From 8cdfb3399a0f35f3c05f89643f3cbd8edf5e41ee Mon Sep 17 00:00:00 2001
From: Rajat Talesra <talesra@talesra-macbookpro.roam.corp.google.com>
Date: Thu, 3 Oct 2019 15:20:32 +0530
Subject: [PATCH 01/28] All xml files for topic-train except layout folder

---
 app/build.gradle                              |  1 +
 .../state_button_primary_background.xml       |  9 +++++++
 .../state_button_transparent_background.xml   |  7 +++++
 app/src/main/res/values/colors.xml            |  4 +++
 app/src/main/res/values/dimens.xml            |  1 +
 app/src/main/res/values/strings.xml           |  3 +++
 app/src/main/res/values/styles.xml            | 27 +++++++++++++++++++
 7 files changed, 52 insertions(+)
 create mode 100644 app/src/main/res/drawable/state_button_primary_background.xml
 create mode 100644 app/src/main/res/drawable/state_button_transparent_background.xml

diff --git a/app/build.gradle b/app/build.gradle
index 22479f62151..5fc0e640fc5 100644
--- a/app/build.gradle
+++ b/app/build.gradle
@@ -61,6 +61,7 @@ dependencies {
       'androidx.constraintlayout:constraintlayout:1.1.3',
       'androidx.core:core-ktx:1.0.2',
       'androidx.lifecycle:lifecycle-runtime-ktx:2.2.0-alpha03',
+      'androidx.recyclerview:recyclerview:1.0.0',
       'com.google.dagger:dagger:2.24',
       "org.jetbrains.kotlin:kotlin-stdlib-jdk7:$kotlin_version",
       "org.jetbrains.kotlinx:kotlinx-coroutines-core:1.2.1",
diff --git a/app/src/main/res/drawable/state_button_primary_background.xml b/app/src/main/res/drawable/state_button_primary_background.xml
new file mode 100644
index 00000000000..c198754b5a8
--- /dev/null
+++ b/app/src/main/res/drawable/state_button_primary_background.xml
@@ -0,0 +1,9 @@
+<?xml version="1.0" encoding="utf-8"?>
+<shape
+  xmlns:android="http://schemas.android.com/apk/res/android"
+  android:shape="rectangle">
+  <corners
+    android:radius="@dimen/state_previous_next_button_radius"/>
+  <solid
+    android:color="@color/colorPrimary"/>
+</shape>
diff --git a/app/src/main/res/drawable/state_button_transparent_background.xml b/app/src/main/res/drawable/state_button_transparent_background.xml
new file mode 100644
index 00000000000..96aa2dbe473
--- /dev/null
+++ b/app/src/main/res/drawable/state_button_transparent_background.xml
@@ -0,0 +1,7 @@
+<?xml version="1.0" encoding="utf-8"?>
+<shape
+  xmlns:android="http://schemas.android.com/apk/res/android"
+  android:shape="rectangle">
+  <solid
+    android:color="@android:color/transparent"/>
+</shape>
diff --git a/app/src/main/res/values/colors.xml b/app/src/main/res/values/colors.xml
index 1f75fbc6809..75cde50851b 100644
--- a/app/src/main/res/values/colors.xml
+++ b/app/src/main/res/values/colors.xml
@@ -9,8 +9,12 @@
   <color name="ic_launcher_background">#26A69A</color>
   <!-- OPPIA COLORS -->
   <color name="oppiaDarkBlue">#2D4A9D</color>
+  <color name="oppiaPrimaryText">#333333</color>
+  <color name="oppiaSecondaryText">#666666</color>
   <!-- BASIC COLORS -->
   <color name="white">#FFFFFF</color>
   <!-- AUDIO COMPONENT -->
   <color name="audioComponentBackground">@color/oppiaDarkBlue</color>
+  <!-- SUBMIT BUTTON INACTIVE -->
+  <color name="submitButtonInactive">#56000000</color>
 </resources>
diff --git a/app/src/main/res/values/dimens.xml b/app/src/main/res/values/dimens.xml
index d9c61be15b7..c96810de821 100755
--- a/app/src/main/res/values/dimens.xml
+++ b/app/src/main/res/values/dimens.xml
@@ -6,4 +6,5 @@
   <dimen name="audio_fragment_corner_radius">8dp</dimen>
   <dimen name="audio_fragment_margin">32dp</dimen>
   <dimen name="cellular_data_dialog_padding">24dp</dimen>
+  <dimen name="state_previous_next_button_radius">4dp</dimen>
 </resources>
diff --git a/app/src/main/res/values/strings.xml b/app/src/main/res/values/strings.xml
index 19d07509e27..de2c8830744 100755
--- a/app/src/main/res/values/strings.xml
+++ b/app/src/main/res/values/strings.xml
@@ -12,4 +12,7 @@
   <string name="cellular_data_alert_dialog_title">Currently on Cellular Data</string>
   <string name="cellular_data_alert_dialog_description">Streaming audio may use a lot of cellular data.</string>
   <string name="cellular_data_alert_dialog_checkbox">Don\'t show this message again</string>
+  <string name="topic_train_master_these_skills">Master These Skills</string>
+  <string name="topic_train_skills_description">Select or unselect skills that you want to practice</string>
+  <string name="topic_train_start">Start</string>
 </resources>
diff --git a/app/src/main/res/values/styles.xml b/app/src/main/res/values/styles.xml
index f5695ca647d..c92ae2e725e 100644
--- a/app/src/main/res/values/styles.xml
+++ b/app/src/main/res/values/styles.xml
@@ -43,4 +43,31 @@
     <item name="android:windowEnterAnimation">@anim/slide_up</item>
     <item name="android:windowExitAnimation">@anim/slide_down</item>
   </style>
+
+  <!-- STATE BUTTON ACTIVE STYLE -->
+  <style name="StateButtonActive" parent="TextAppearance.AppCompat.Widget.Button">
+    <item name="android:layout_width">wrap_content</item>
+    <item name="android:layout_height">wrap_content</item>
+    <item name="android:background">@drawable/state_button_primary_background</item>
+    <item name="android:paddingTop">8dp</item>
+    <item name="android:paddingBottom">8dp</item>
+    <item name="android:paddingStart">16dp</item>
+    <item name="android:paddingEnd">16dp</item>
+    <item name="android:textAllCaps">true</item>
+    <item name="android:textColor">@color/white</item>
+    <item name="android:textSize">14sp</item>
+    <item name="android:clickable">true</item>
+  </style>
+
+  <!-- STATE BUTTON INACTIVE STYLE -->
+  <style name="StateButtonInactive" parent="TextAppearance.AppCompat.Widget.Button">
+    <item name="android:layout_width">wrap_content</item>
+    <item name="android:layout_height">wrap_content</item>
+    <item name="android:padding">8dp</item>
+    <item name="android:textAllCaps">true</item>
+    <item name="android:background">@android:color/transparent</item>
+    <item name="android:textColor">#56000000</item>
+    <item name="android:textSize">14sp</item>
+    <item name="android:clickable">false</item>
+  </style>
 </resources>

From afd819626417fbffec8d0115703859535cbe0ca0 Mon Sep 17 00:00:00 2001
From: Rajat Talesra <talesra@talesra-macbookpro.roam.corp.google.com>
Date: Thu, 3 Oct 2019 15:24:56 +0530
Subject: [PATCH 02/28] Skill item related files

---
 .../oppia/app/topic/train/SkillInterface.kt   |  9 ++++
 .../app/topic/train/SkillSelectionAdapter.kt  | 52 +++++++++++++++++++
 .../res/layout/topic_train_skill_view.xml     | 28 ++++++++++
 3 files changed, 89 insertions(+)
 create mode 100644 app/src/main/java/org/oppia/app/topic/train/SkillInterface.kt
 create mode 100644 app/src/main/java/org/oppia/app/topic/train/SkillSelectionAdapter.kt
 create mode 100644 app/src/main/res/layout/topic_train_skill_view.xml

diff --git a/app/src/main/java/org/oppia/app/topic/train/SkillInterface.kt b/app/src/main/java/org/oppia/app/topic/train/SkillInterface.kt
new file mode 100644
index 00000000000..113ed35f4bc
--- /dev/null
+++ b/app/src/main/java/org/oppia/app/topic/train/SkillInterface.kt
@@ -0,0 +1,9 @@
+package org.oppia.app.topic.train
+
+/** Interface to update the selectedSkillList in [TopicTrainFragmentPresenter]. */
+interface SkillInterface {
+  /** This skill will get added to selectedSkillList in [TopicTrainFragmentPresenter] */
+  fun skillSelected(skill: String)
+  /** This skill will get removed from selectedSkillList in [TopicTrainFragmentPresenter] */
+  fun skillUnselected(skill: String)
+}
diff --git a/app/src/main/java/org/oppia/app/topic/train/SkillSelectionAdapter.kt b/app/src/main/java/org/oppia/app/topic/train/SkillSelectionAdapter.kt
new file mode 100644
index 00000000000..5ddeb7d9f9f
--- /dev/null
+++ b/app/src/main/java/org/oppia/app/topic/train/SkillSelectionAdapter.kt
@@ -0,0 +1,52 @@
+package org.oppia.app.topic.train;
+
+import android.view.LayoutInflater
+import android.view.ViewGroup
+import androidx.databinding.DataBindingUtil
+import androidx.databinding.ViewDataBinding
+import androidx.databinding.library.baseAdapters.BR
+import androidx.recyclerview.widget.RecyclerView
+import kotlinx.android.synthetic.main.topic_train_skill_view.view.*
+import org.oppia.app.R
+import org.oppia.app.databinding.TopicTrainSkillViewBinding
+
+/** Adapter to bind skills to [RecyclerView] inside [TopicTrainFragment]. **/
+class SkillSelectionAdapter(
+  private val skillList: List<String>,
+  private val skillInterface: SkillInterface
+) : RecyclerView.Adapter<RecyclerView.ViewHolder>() {
+
+  override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): RecyclerView.ViewHolder {
+    val inflater = LayoutInflater.from(parent.context)
+    val binding =
+      DataBindingUtil.inflate<TopicTrainSkillViewBinding>(
+        inflater,
+        R.layout.topic_train_skill_view,
+        parent,
+        false
+      )
+    return SkillViewHolder(binding)
+  }
+
+  override fun onBindViewHolder(holder: RecyclerView.ViewHolder, position: Int) {
+    (holder as SkillViewHolder).bind(skillList[position], position)
+  }
+
+  override fun getItemCount(): Int {
+    return skillList.size
+  }
+
+  private inner class SkillViewHolder(val binding: ViewDataBinding) : RecyclerView.ViewHolder(binding.root) {
+    internal fun bind(rawString: String?, position: Int) {
+      binding.setVariable(BR.skill, rawString)
+      binding.root.skill_check_box.setOnCheckedChangeListener { buttonView, isChecked ->
+        val skill = skillList[position]
+        if (isChecked) {
+          skillInterface.skillSelected(skill)
+        } else {
+          skillInterface.skillUnselected(skill)
+        }
+      }
+    }
+  }
+}
diff --git a/app/src/main/res/layout/topic_train_skill_view.xml b/app/src/main/res/layout/topic_train_skill_view.xml
new file mode 100644
index 00000000000..a8ac2d9c8cb
--- /dev/null
+++ b/app/src/main/res/layout/topic_train_skill_view.xml
@@ -0,0 +1,28 @@
+<?xml version="1.0" encoding="utf-8"?>
+<layout
+  xmlns:android="http://schemas.android.com/apk/res/android"
+  xmlns:app="http://schemas.android.com/apk/res-auto">
+  <data>
+    <variable
+      name="skill"
+      type="java.lang.String"/>
+  </data>
+  <androidx.constraintlayout.widget.ConstraintLayout
+    android:layout_width="match_parent"
+    android:layout_height="wrap_content">
+    <CheckBox
+      android:id="@+id/skill_check_box"
+      android:layout_width="match_parent"
+      android:layout_height="wrap_content"
+      android:layout_margin="4dp"
+      android:drawablePadding="4dp"
+      android:gravity="center_vertical"
+      android:text="@{skill}"
+      android:textColor="@color/oppiaPrimaryText"
+      android:textSize="16sp"
+      app:layout_constraintBottom_toBottomOf="parent"
+      app:layout_constraintEnd_toEndOf="parent"
+      app:layout_constraintStart_toStartOf="parent"
+      app:layout_constraintTop_toTopOf="parent"/>
+  </androidx.constraintlayout.widget.ConstraintLayout>
+</layout>

From 87977abdcc98f35dfed933c7efde1f7e9b03d9bc Mon Sep 17 00:00:00 2001
From: Rajat Talesra <talesra@talesra-macbookpro.roam.corp.google.com>
Date: Thu, 3 Oct 2019 15:28:18 +0530
Subject: [PATCH 03/28] TopicTrainFragment implementation

---
 .../app/topic/train/TopicTrainFragment.kt     |  5 ++
 .../train/TopicTrainFragmentPresenter.kt      | 45 +++++++++++++-
 .../app/topic/train/TopicTrainViewModel.kt    | 16 +++++
 .../main/res/layout/topic_train_fragment.xml  | 59 +++++++++++++++++--
 4 files changed, 117 insertions(+), 8 deletions(-)
 create mode 100644 app/src/main/java/org/oppia/app/topic/train/TopicTrainViewModel.kt

diff --git a/app/src/main/java/org/oppia/app/topic/train/TopicTrainFragment.kt b/app/src/main/java/org/oppia/app/topic/train/TopicTrainFragment.kt
index 4d1a5062f9e..598852a3d56 100644
--- a/app/src/main/java/org/oppia/app/topic/train/TopicTrainFragment.kt
+++ b/app/src/main/java/org/oppia/app/topic/train/TopicTrainFragment.kt
@@ -21,4 +21,9 @@ class TopicTrainFragment : InjectableFragment() {
   override fun onCreateView(inflater: LayoutInflater, container: ViewGroup?, savedInstanceState: Bundle?): View? {
     return topicTrainFragmentPresenter.handleCreateView(inflater, container)
   }
+
+  fun submitButtonClicked(){
+    // List of selected skills when submit button is clicked.
+    val skillList = topicTrainFragmentPresenter.getSelectedSkillList()
+  }
 }
diff --git a/app/src/main/java/org/oppia/app/topic/train/TopicTrainFragmentPresenter.kt b/app/src/main/java/org/oppia/app/topic/train/TopicTrainFragmentPresenter.kt
index af436a7e294..df846f1c27d 100644
--- a/app/src/main/java/org/oppia/app/topic/train/TopicTrainFragmentPresenter.kt
+++ b/app/src/main/java/org/oppia/app/topic/train/TopicTrainFragmentPresenter.kt
@@ -4,20 +4,61 @@ import android.view.LayoutInflater
 import android.view.View
 import android.view.ViewGroup
 import androidx.fragment.app.Fragment
+import androidx.recyclerview.widget.LinearLayoutManager
 import org.oppia.app.databinding.TopicTrainFragmentBinding
 import org.oppia.app.fragment.FragmentScope
+import org.oppia.app.viewmodel.ViewModelProvider
 import javax.inject.Inject
 
 /** The presenter for [TopicTrainFragment]. */
 @FragmentScope
 class TopicTrainFragmentPresenter @Inject constructor(
-  private val fragment: Fragment
-) {
+  private val fragment: Fragment,
+  private val viewModelProvider: ViewModelProvider<TopicTrainViewModel>
+) : SkillInterface {
+  private val selectedSkillList = ArrayList<String>()
+
   fun handleCreateView(inflater: LayoutInflater, container: ViewGroup?): View? {
+    val skillAdapter = SkillSelectionAdapter(dummySkillList(), this)
+
     val binding = TopicTrainFragmentBinding.inflate(inflater, container, /* attachToRoot= */ false)
+    binding.skillRecyclerView.apply {
+      adapter = skillAdapter
+      layoutManager = LinearLayoutManager(context)
+    }
     binding.let {
+      it.viewModel = getTopicTrainViewModel()
       it.lifecycleOwner = fragment
     }
     return binding.root
   }
+
+  private fun getTopicTrainViewModel(): TopicTrainViewModel {
+    return viewModelProvider.getForFragment(fragment, TopicTrainViewModel::class.java)
+  }
+
+  override fun skillSelected(skill: String) {
+    selectedSkillList.add(skill)
+    getTopicTrainViewModel().selectedSkillList(selectedSkillList)
+  }
+
+  override fun skillUnselected(skill: String) {
+    selectedSkillList.remove(skill)
+    getTopicTrainViewModel().selectedSkillList(selectedSkillList)
+  }
+
+  private fun dummySkillList(): List<String> {
+    val skillList = ArrayList<String>()
+    skillList.add("Identify the Parts of a Fraction")
+    skillList.add("Writing Fractions")
+    skillList.add("Equivalent Fractions")
+    skillList.add("Mixed Numbers and Improper Fractions")
+    skillList.add("Comparing Fractions")
+    skillList.add("Adding and Subtracting Fractions")
+    skillList.add("Multiplying Fractions")
+    skillList.add("Dividing Fractions")
+    return skillList
+  }
+
+  fun getSelectedSkillList() = selectedSkillList
 }
diff --git a/app/src/main/java/org/oppia/app/topic/train/TopicTrainViewModel.kt b/app/src/main/java/org/oppia/app/topic/train/TopicTrainViewModel.kt
new file mode 100644
index 00000000000..6cbbb2d31c6
--- /dev/null
+++ b/app/src/main/java/org/oppia/app/topic/train/TopicTrainViewModel.kt
@@ -0,0 +1,16 @@
+package org.oppia.app.topic.train
+
+import androidx.databinding.ObservableField
+import androidx.lifecycle.ViewModel
+import org.oppia.app.fragment.FragmentScope
+import javax.inject.Inject
+
+/** [ViewModel] for showing skills in train fragment. */
+@FragmentScope
+class TopicTrainViewModel @Inject constructor() : ViewModel() {
+  var isSubmitButtonActive = ObservableField<Boolean>(false)
+
+  fun selectedSkillList(selectedSkillList: ArrayList<String>) {
+    isSubmitButtonActive.set(selectedSkillList.isNotEmpty())
+  }
+}
diff --git a/app/src/main/res/layout/topic_train_fragment.xml b/app/src/main/res/layout/topic_train_fragment.xml
index e9b0824c1b7..4668220c3d9 100644
--- a/app/src/main/res/layout/topic_train_fragment.xml
+++ b/app/src/main/res/layout/topic_train_fragment.xml
@@ -2,17 +2,64 @@
 <layout
   xmlns:android="http://schemas.android.com/apk/res/android"
   xmlns:app="http://schemas.android.com/apk/res-auto">
+  <data>
+    <import type="android.view.View"/>
+    <variable
+      name="topicTrainFragment"
+      type="org.oppia.app.topic.train.TopicTrainFragment"/>
+    <variable
+      name="viewModel"
+      type="org.oppia.app.topic.train.TopicTrainViewModel"/>
+  </data>
   <androidx.constraintlayout.widget.ConstraintLayout
     android:layout_width="match_parent"
     android:layout_height="match_parent">
-    <TextView
-      android:id="@+id/dummy_text_view"
-      android:layout_width="wrap_content"
-      android:layout_height="wrap_content"
-      android:text="This is dummy TextView for testing"
+    <ScrollView
+      android:layout_width="match_parent"
+      android:layout_height="match_parent"
+      android:overScrollMode="never"
+      android:scrollbars="none"
       app:layout_constraintBottom_toBottomOf="parent"
       app:layout_constraintEnd_toEndOf="parent"
       app:layout_constraintStart_toStartOf="parent"
-      app:layout_constraintTop_toTopOf="parent"/>
+      app:layout_constraintTop_toTopOf="parent">
+      <LinearLayout
+        android:layout_width="match_parent"
+        android:layout_height="wrap_content"
+        android:orientation="vertical"
+        android:padding="32dp">
+        <TextView
+          android:id="@+id/master_skills_text_view"
+          android:layout_width="wrap_content"
+          android:layout_height="wrap_content"
+          android:text="@string/topic_train_master_these_skills"
+          android:textColor="@color/oppiaPrimaryText"
+          android:textSize="20sp"/>
+        <TextView
+          android:id="@+id/skills_description_text_view"
+          android:layout_width="wrap_content"
+          android:layout_height="wrap_content"
+          android:layout_marginTop="16dp"
+          android:text="@string/topic_train_skills_description"
+          android:textColor="@color/oppiaSecondaryText"
+          android:textSize="16sp"/>
+        <androidx.recyclerview.widget.RecyclerView
+          android:id="@+id/skill_recycler_view"
+          android:layout_width="match_parent"
+          android:layout_height="wrap_content"
+          android:layout_marginTop="16dp"
+          app:layoutManager="androidx.recyclerview.widget.LinearLayoutManager"/>
+        <Button
+          android:id="@+id/topic_train_start_button"
+          style="@style/StateButtonInactive"
+          android:layout_gravity="center_horizontal"
+          android:layout_marginTop="24dp"
+          android:background="@{viewModel.isSubmitButtonActive() ? @drawable/state_button_primary_background :@drawable/state_button_transparent_background}"
+          android:clickable="@{viewModel.isSubmitButtonActive()}"
+          android:onClick="@{(v) -> topicTrainFragment.submitButtonClicked()}"
+          android:text="@string/topic_train_start"
+          android:textColor="@{viewModel.isSubmitButtonActive()? @color/white : @color/submitButtonInactive}"/>
+      </LinearLayout>
+    </ScrollView>
   </androidx.constraintlayout.widget.ConstraintLayout>
 </layout>

From 456d1299dd85899b28802b2c1a00192e3c8071b6 Mon Sep 17 00:00:00 2001
From: Rajat Talesra <talesra@talesra-macbookpro.roam.corp.google.com>
Date: Thu, 3 Oct 2019 15:54:25 +0530
Subject: [PATCH 04/28] Topic Train Test Case

---
 .../app/topic/train/TopicTrainFragmentTest.kt   | 17 +++++++++++++----
 1 file changed, 13 insertions(+), 4 deletions(-)

diff --git a/app/src/sharedTest/java/org/oppia/app/topic/train/TopicTrainFragmentTest.kt b/app/src/sharedTest/java/org/oppia/app/topic/train/TopicTrainFragmentTest.kt
index b55c8fa420f..051a6531429 100644
--- a/app/src/sharedTest/java/org/oppia/app/topic/train/TopicTrainFragmentTest.kt
+++ b/app/src/sharedTest/java/org/oppia/app/topic/train/TopicTrainFragmentTest.kt
@@ -4,7 +4,11 @@ import android.app.Application
 import android.content.Context
 import androidx.test.core.app.ActivityScenario
 import androidx.test.espresso.Espresso.onView
+import androidx.test.espresso.action.ViewActions.click
+import androidx.test.espresso.action.ViewActions.scrollTo
 import androidx.test.espresso.assertion.ViewAssertions.matches
+import androidx.test.espresso.matcher.ViewMatchers.isClickable
+import androidx.test.espresso.matcher.ViewMatchers.isNotChecked
 import androidx.test.espresso.matcher.ViewMatchers.withId
 import androidx.test.espresso.matcher.ViewMatchers.withText
 import androidx.test.ext.junit.runners.AndroidJUnit4
@@ -13,10 +17,11 @@ import dagger.Component
 import dagger.Module
 import dagger.Provides
 import kotlinx.coroutines.CoroutineDispatcher
+import org.hamcrest.Matchers.not
 import org.junit.Test
 import org.junit.runner.RunWith
 import org.oppia.app.R
-import org.oppia.app.topic.TopicActivity
+import org.oppia.app.home.HomeActivity
 import org.oppia.util.threading.BackgroundDispatcher
 import org.oppia.util.threading.BlockingDispatcher
 import javax.inject.Singleton
@@ -26,9 +31,13 @@ import javax.inject.Singleton
 class TopicTrainFragmentTest {
 
   @Test
-  fun testTopicTrainFragment_loadFragment_textIsDisplayed() {
-    ActivityScenario.launch(TopicActivity::class.java).use {
-      onView(withId(R.id.dummy_text_view)).check(matches(withText("This is dummy TextView for testing")))
+  fun testTopicTrainFragment_loadFragment_selectSkills_submitButtonIsActivated() {
+    ActivityScenario.launch(HomeActivity::class.java).use {
+      onView(withId(R.id.master_skills_text_view)).check(matches(withText(R.string.topic_train_master_these_skills)))
+      onView(withId(R.id.topic_train_start_button)).check(matches(not(isClickable())))
+      onView(withText("Writing Fractions")).check(matches(isNotChecked())).perform(scrollTo(), click())
+      onView(withText("Equivalent Fractions")).check(matches(isNotChecked())).perform(scrollTo(), click())
+      onView(withId(R.id.topic_train_start_button)).check(matches(isClickable()))
     }
   }
 

From e39fa93a5d658435ef63d3b0e20f2c72fa056a90 Mon Sep 17 00:00:00 2001
From: Rajat Talesra <talesra@talesra-macbookpro.roam.corp.google.com>
Date: Sat, 5 Oct 2019 15:11:21 +0530
Subject: [PATCH 05/28] Domain layer code integration

---
 app/src/main/AndroidManifest.xml              |  2 +-
 .../questionplayer/QuestionPlayerActivity.kt  |  3 +-
 .../questionplayer/QuestionPlayerFragment.kt  |  2 +-
 .../QuestionPlayerFragmentPresenter.kt        |  2 +-
 .../app/topic/train/SkillSelectionAdapter.kt  |  5 +-
 .../oppia/app/topic/train/SkillSelector.kt    |  6 +-
 .../app/topic/train/TopicTrainFragment.kt     |  9 +--
 .../train/TopicTrainFragmentPresenter.kt      | 73 ++++++++++++++-----
 .../app/topic/train/TopicTrainViewModel.kt    |  3 +-
 .../main/res/layout/topic_train_fragment.xml  |  8 +-
 .../res/layout/topic_train_skill_view.xml     |  4 +-
 app/src/main/res/values/styles.xml            |  1 -
 12 files changed, 76 insertions(+), 42 deletions(-)

diff --git a/app/src/main/AndroidManifest.xml b/app/src/main/AndroidManifest.xml
index bcbe1a3c526..d5754174871 100644
--- a/app/src/main/AndroidManifest.xml
+++ b/app/src/main/AndroidManifest.xml
@@ -28,4 +28,4 @@
       android:theme="@style/SplashScreenTheme">
     </activity>
   </application>
-</manifest>
\ No newline at end of file
+</manifest>
diff --git a/app/src/main/java/org/oppia/app/topic/questionplayer/QuestionPlayerActivity.kt b/app/src/main/java/org/oppia/app/topic/questionplayer/QuestionPlayerActivity.kt
index a10681fa687..0faf20086ca 100644
--- a/app/src/main/java/org/oppia/app/topic/questionplayer/QuestionPlayerActivity.kt
+++ b/app/src/main/java/org/oppia/app/topic/questionplayer/QuestionPlayerActivity.kt
@@ -1,6 +1,7 @@
 package org.oppia.app.topic.questionplayer
 
 import android.os.Bundle
+import android.util.Log
 import org.oppia.app.activity.InjectableAppCompatActivity
 import javax.inject.Inject
 
@@ -20,6 +21,6 @@ class QuestionPlayerActivity : InjectableAppCompatActivity() {
 
   private fun getSkillList(): ArrayList<String> {
     val topicTrainIntent = intent
-    return topicTrainIntent.getStringArrayListExtra("SKILL_LIST")
+    return topicTrainIntent.getStringArrayListExtra("SKILL_ID_LIST")
   }
 }
diff --git a/app/src/main/java/org/oppia/app/topic/questionplayer/QuestionPlayerFragment.kt b/app/src/main/java/org/oppia/app/topic/questionplayer/QuestionPlayerFragment.kt
index 966e5dcb5c6..c3b2ce22195 100644
--- a/app/src/main/java/org/oppia/app/topic/questionplayer/QuestionPlayerFragment.kt
+++ b/app/src/main/java/org/oppia/app/topic/questionplayer/QuestionPlayerFragment.kt
@@ -21,4 +21,4 @@ class QuestionPlayerFragment: InjectableFragment(){
   override fun onCreateView(inflater: LayoutInflater, container: ViewGroup?, savedInstanceState: Bundle?): View? {
     return questionPlayerFragmentPresenter.handleCreateView(inflater, container)
   }
-}
\ No newline at end of file
+}
diff --git a/app/src/main/java/org/oppia/app/topic/questionplayer/QuestionPlayerFragmentPresenter.kt b/app/src/main/java/org/oppia/app/topic/questionplayer/QuestionPlayerFragmentPresenter.kt
index 1d7211e308b..92d7e7b97ad 100644
--- a/app/src/main/java/org/oppia/app/topic/questionplayer/QuestionPlayerFragmentPresenter.kt
+++ b/app/src/main/java/org/oppia/app/topic/questionplayer/QuestionPlayerFragmentPresenter.kt
@@ -8,7 +8,7 @@ import org.oppia.app.databinding.QuestionPlayerFragmentBinding
 import org.oppia.app.fragment.FragmentScope
 import javax.inject.Inject
 
-/** The controller for [QuestionPlayerFragment]. */
+/** The presenter for [QuestionPlayerFragment]. */
 @FragmentScope
 class QuestionPlayerFragmentPresenter @Inject constructor(
   private val fragment: Fragment
diff --git a/app/src/main/java/org/oppia/app/topic/train/SkillSelectionAdapter.kt b/app/src/main/java/org/oppia/app/topic/train/SkillSelectionAdapter.kt
index 7b45fbef6bd..57c30f539cd 100644
--- a/app/src/main/java/org/oppia/app/topic/train/SkillSelectionAdapter.kt
+++ b/app/src/main/java/org/oppia/app/topic/train/SkillSelectionAdapter.kt
@@ -9,11 +9,12 @@ import androidx.recyclerview.widget.RecyclerView
 import kotlinx.android.synthetic.main.topic_train_skill_view.view.*
 import org.oppia.app.R
 import org.oppia.app.databinding.TopicTrainSkillViewBinding
+import org.oppia.app.model.SkillSummary
 
 // TODO(#172): Make use of generic data-binding-enabled RecyclerView adapter.
 /** Adapter to bind skills to [RecyclerView] inside [TopicTrainFragment]. */
 class SkillSelectionAdapter(
-  private val skillList: List<String>,
+  private val skillList: List<SkillSummary>,
   private val skillSelector: SkillSelector
 ) : RecyclerView.Adapter<RecyclerView.ViewHolder>() {
 
@@ -38,7 +39,7 @@ class SkillSelectionAdapter(
   }
 
   private inner class SkillViewHolder(val binding: ViewDataBinding) : RecyclerView.ViewHolder(binding.root) {
-    internal fun bind(rawString: String?, position: Int) {
+    internal fun bind(rawString: SkillSummary, position: Int) {
       binding.setVariable(BR.skill, rawString)
       binding.root.skill_check_box.setOnCheckedChangeListener { buttonView, isChecked ->
         val skill = skillList[position]
diff --git a/app/src/main/java/org/oppia/app/topic/train/SkillSelector.kt b/app/src/main/java/org/oppia/app/topic/train/SkillSelector.kt
index 2888b705161..00cc51efd86 100644
--- a/app/src/main/java/org/oppia/app/topic/train/SkillSelector.kt
+++ b/app/src/main/java/org/oppia/app/topic/train/SkillSelector.kt
@@ -1,9 +1,11 @@
 package org.oppia.app.topic.train
 
+import org.oppia.app.model.SkillSummary
+
 /** Interface to update the selectedSkillList in [TopicTrainFragmentPresenter]. */
 interface SkillSelector {
   /** This skill will get added to selectedSkillList in [TopicTrainFragmentPresenter]. */
-  fun skillSelected(skill: String)
+  fun skillSelected(skill: SkillSummary)
   /** This skill will get removed from selectedSkillList in [TopicTrainFragmentPresenter]. */
-  fun skillUnselected(skill: String)
+  fun skillUnselected(skill: SkillSummary)
 }
diff --git a/app/src/main/java/org/oppia/app/topic/train/TopicTrainFragment.kt b/app/src/main/java/org/oppia/app/topic/train/TopicTrainFragment.kt
index 865aaf7634e..bfa26bef8ef 100644
--- a/app/src/main/java/org/oppia/app/topic/train/TopicTrainFragment.kt
+++ b/app/src/main/java/org/oppia/app/topic/train/TopicTrainFragment.kt
@@ -3,10 +3,12 @@ package org.oppia.app.topic.train
 import android.content.Context
 import android.content.Intent
 import android.os.Bundle
+import android.util.Log
 import android.view.LayoutInflater
 import android.view.View
 import android.view.ViewGroup
 import org.oppia.app.fragment.InjectableFragment
+import org.oppia.app.topic.questionplayer.QuestionPlayerActivity
 import javax.inject.Inject
 
 /** Fragment that contains skills for topic train mode. */
@@ -22,11 +24,4 @@ class TopicTrainFragment : InjectableFragment() {
   override fun onCreateView(inflater: LayoutInflater, container: ViewGroup?, savedInstanceState: Bundle?): View? {
     return topicTrainFragmentPresenter.handleCreateView(inflater, container)
   }
-
-  fun submitButtonClicked() {
-    val skillList = topicTrainFragmentPresenter.getSelectedSkillList()
-    val questionPlayerIntent = Intent()
-    questionPlayerIntent.putStringArrayListExtra("SKILL_LIST", skillList)
-    startActivity(questionPlayerIntent)
-  }
 }
diff --git a/app/src/main/java/org/oppia/app/topic/train/TopicTrainFragmentPresenter.kt b/app/src/main/java/org/oppia/app/topic/train/TopicTrainFragmentPresenter.kt
index 19af3f69e2e..9957600777a 100644
--- a/app/src/main/java/org/oppia/app/topic/train/TopicTrainFragmentPresenter.kt
+++ b/app/src/main/java/org/oppia/app/topic/train/TopicTrainFragmentPresenter.kt
@@ -1,64 +1,99 @@
 package org.oppia.app.topic.train
 
+import android.content.Context
+import android.content.Intent
 import android.view.LayoutInflater
 import android.view.View
 import android.view.ViewGroup
 import androidx.fragment.app.Fragment
+import androidx.lifecycle.LiveData
+import androidx.lifecycle.Observer
+import androidx.lifecycle.Transformations
 import androidx.recyclerview.widget.LinearLayoutManager
+import org.oppia.app.application.ApplicationContext
 import org.oppia.app.databinding.TopicTrainFragmentBinding
 import org.oppia.app.fragment.FragmentScope
+import org.oppia.app.model.SkillSummary
+import org.oppia.app.model.Topic
+import org.oppia.app.topic.questionplayer.QuestionPlayerActivity
 import org.oppia.app.viewmodel.ViewModelProvider
+import org.oppia.domain.topic.TEST_TOPIC_ID_0
+import org.oppia.domain.topic.TopicController
+import org.oppia.util.data.AsyncResult
+import org.oppia.util.logging.Logger
 import javax.inject.Inject
 
 /** The presenter for [TopicTrainFragment]. */
 @FragmentScope
 class TopicTrainFragmentPresenter @Inject constructor(
+  @ApplicationContext private val context: Context,
   private val fragment: Fragment,
+  private val logger: Logger,
+  private val topicController: TopicController,
   private val viewModelProvider: ViewModelProvider<TopicTrainViewModel>
 ) : SkillSelector {
-  private val selectedSkillList = ArrayList<String>()
+  val selectedSkillList = ArrayList<SkillSummary>()
 
   fun handleCreateView(inflater: LayoutInflater, container: ViewGroup?): View? {
-    val skillAdapter = SkillSelectionAdapter(dummySkillList(), this)
-
     val binding = TopicTrainFragmentBinding.inflate(inflater, container, /* attachToRoot= */ false)
     binding.skillRecyclerView.apply {
-      adapter = skillAdapter
       layoutManager = LinearLayoutManager(context)
     }
     binding.let {
       it.viewModel = getTopicTrainViewModel()
       it.lifecycleOwner = fragment
     }
+    getSkillList(binding)
     return binding.root
   }
 
+  // TODO(#135): Get this topic-id or get skillList from from [TopicFragment].
+  private val topicResultLiveData: LiveData<AsyncResult<Topic>> by lazy {
+    topicController.getTopic(TEST_TOPIC_ID_0)
+  }
+
+  private fun getSkillList(binding: TopicTrainFragmentBinding) {
+    topicLiveData.observe(fragment, Observer<Topic> { result ->
+      val skillAdapter = SkillSelectionAdapter(result.skillList, this)
+      binding.skillRecyclerView.adapter = skillAdapter
+    })
+  }
+
+  private val topicLiveData: LiveData<Topic> by lazy { getTopicList() }
+
+  private fun getTopicList(): LiveData<Topic> {
+    return Transformations.map(topicResultLiveData, ::processTopicResult)
+  }
+
+  private fun processTopicResult(topic: AsyncResult<Topic>): Topic {
+    if (topic.isFailure()) {
+      logger.e("TopicTrainFragmentPresenter", "Failed to retrieve ephemeral state ${topic.getErrorOrNull()}")
+    }
+    return topic.getOrDefault(Topic.getDefaultInstance())
+  }
+
   private fun getTopicTrainViewModel(): TopicTrainViewModel {
     return viewModelProvider.getForFragment(fragment, TopicTrainViewModel::class.java)
   }
 
-  override fun skillSelected(skill: String) {
+  override fun skillSelected(skill: SkillSummary) {
     selectedSkillList.add(skill)
     getTopicTrainViewModel().selectedSkillList(selectedSkillList)
   }
 
-  override fun skillUnselected(skill: String) {
+  override fun skillUnselected(skill: SkillSummary) {
     selectedSkillList.remove(skill)
     getTopicTrainViewModel().selectedSkillList(selectedSkillList)
   }
 
-  private fun dummySkillList(): List<String> {
-    val skillList = ArrayList<String>()
-    skillList.add("Identify the Parts of a Fraction")
-    skillList.add("Writing Fractions")
-    skillList.add("Equivalent Fractions")
-    skillList.add("Mixed Numbers and Improper Fractions")
-    skillList.add("Comparing Fractions")
-    skillList.add("Adding and Subtracting Fractions")
-    skillList.add("Multiplying Fractions")
-    skillList.add("Dividing Fractions")
-    return skillList
+  fun startButtonClicked(v: View) {
+    val skillList = selectedSkillList
+    val skillIdList = ArrayList<String>()
+    for (skill in skillList) {
+      skillIdList.add(skill.skillId)
+    }
+    val questionPlayerIntent = Intent(context, QuestionPlayerActivity::class.java)
+    questionPlayerIntent.putStringArrayListExtra("SKILL_ID_LIST", skillIdList)
+    context.startActivity(questionPlayerIntent)
   }
-
-  fun getSelectedSkillList() = selectedSkillList
 }
diff --git a/app/src/main/java/org/oppia/app/topic/train/TopicTrainViewModel.kt b/app/src/main/java/org/oppia/app/topic/train/TopicTrainViewModel.kt
index 6cbbb2d31c6..a1e5f9e9876 100644
--- a/app/src/main/java/org/oppia/app/topic/train/TopicTrainViewModel.kt
+++ b/app/src/main/java/org/oppia/app/topic/train/TopicTrainViewModel.kt
@@ -3,6 +3,7 @@ package org.oppia.app.topic.train
 import androidx.databinding.ObservableField
 import androidx.lifecycle.ViewModel
 import org.oppia.app.fragment.FragmentScope
+import org.oppia.app.model.SkillSummary
 import javax.inject.Inject
 
 /** [ViewModel] for showing skills in train fragment. */
@@ -10,7 +11,7 @@ import javax.inject.Inject
 class TopicTrainViewModel @Inject constructor() : ViewModel() {
   var isSubmitButtonActive = ObservableField<Boolean>(false)
 
-  fun selectedSkillList(selectedSkillList: ArrayList<String>) {
+  fun selectedSkillList(selectedSkillList: ArrayList<SkillSummary>) {
     isSubmitButtonActive.set(selectedSkillList.isNotEmpty())
   }
 }
diff --git a/app/src/main/res/layout/topic_train_fragment.xml b/app/src/main/res/layout/topic_train_fragment.xml
index 4668220c3d9..50d34d69427 100644
--- a/app/src/main/res/layout/topic_train_fragment.xml
+++ b/app/src/main/res/layout/topic_train_fragment.xml
@@ -4,12 +4,12 @@
   xmlns:app="http://schemas.android.com/apk/res-auto">
   <data>
     <import type="android.view.View"/>
-    <variable
-      name="topicTrainFragment"
-      type="org.oppia.app.topic.train.TopicTrainFragment"/>
     <variable
       name="viewModel"
       type="org.oppia.app.topic.train.TopicTrainViewModel"/>
+    <variable
+      name="presenter"
+      type="org.oppia.app.topic.train.TopicTrainFragmentPresenter"/>
   </data>
   <androidx.constraintlayout.widget.ConstraintLayout
     android:layout_width="match_parent"
@@ -56,7 +56,7 @@
           android:layout_marginTop="24dp"
           android:background="@{viewModel.isSubmitButtonActive() ? @drawable/state_button_primary_background :@drawable/state_button_transparent_background}"
           android:clickable="@{viewModel.isSubmitButtonActive()}"
-          android:onClick="@{(v) -> topicTrainFragment.submitButtonClicked()}"
+          android:onClick="@{presenter::startButtonClicked}"
           android:text="@string/topic_train_start"
           android:textColor="@{viewModel.isSubmitButtonActive()? @color/white : @color/submitButtonInactive}"/>
       </LinearLayout>
diff --git a/app/src/main/res/layout/topic_train_skill_view.xml b/app/src/main/res/layout/topic_train_skill_view.xml
index a8ac2d9c8cb..b25416135f2 100644
--- a/app/src/main/res/layout/topic_train_skill_view.xml
+++ b/app/src/main/res/layout/topic_train_skill_view.xml
@@ -5,7 +5,7 @@
   <data>
     <variable
       name="skill"
-      type="java.lang.String"/>
+      type="org.oppia.app.model.SkillSummaryOrBuilder"/>
   </data>
   <androidx.constraintlayout.widget.ConstraintLayout
     android:layout_width="match_parent"
@@ -17,7 +17,7 @@
       android:layout_margin="4dp"
       android:drawablePadding="4dp"
       android:gravity="center_vertical"
-      android:text="@{skill}"
+      android:text="@{skill.description}"
       android:textColor="@color/oppiaPrimaryText"
       android:textSize="16sp"
       app:layout_constraintBottom_toBottomOf="parent"
diff --git a/app/src/main/res/values/styles.xml b/app/src/main/res/values/styles.xml
index c92ae2e725e..b36413eb4a9 100644
--- a/app/src/main/res/values/styles.xml
+++ b/app/src/main/res/values/styles.xml
@@ -68,6 +68,5 @@
     <item name="android:background">@android:color/transparent</item>
     <item name="android:textColor">#56000000</item>
     <item name="android:textSize">14sp</item>
-    <item name="android:clickable">false</item>
   </style>
 </resources>

From 1cd605fd529afaf15b45b89e813e58c56b4701a9 Mon Sep 17 00:00:00 2001
From: Rajat Talesra <talesra@talesra-macbookpro.roam.corp.google.com>
Date: Sat, 5 Oct 2019 15:50:24 +0530
Subject: [PATCH 06/28] Start button activated

---
 .../app/topic/train/TopicTrainFragmentPresenter.kt    | 11 ++++-------
 .../org/oppia/app/topic/train/TopicTrainViewModel.kt  | 10 +++++++++-
 app/src/main/res/layout/topic_train_fragment.xml      |  2 +-
 3 files changed, 14 insertions(+), 9 deletions(-)

diff --git a/app/src/main/java/org/oppia/app/topic/train/TopicTrainFragmentPresenter.kt b/app/src/main/java/org/oppia/app/topic/train/TopicTrainFragmentPresenter.kt
index 9957600777a..29b8441a842 100644
--- a/app/src/main/java/org/oppia/app/topic/train/TopicTrainFragmentPresenter.kt
+++ b/app/src/main/java/org/oppia/app/topic/train/TopicTrainFragmentPresenter.kt
@@ -1,6 +1,5 @@
 package org.oppia.app.topic.train
 
-import android.content.Context
 import android.content.Intent
 import android.view.LayoutInflater
 import android.view.View
@@ -10,7 +9,6 @@ import androidx.lifecycle.LiveData
 import androidx.lifecycle.Observer
 import androidx.lifecycle.Transformations
 import androidx.recyclerview.widget.LinearLayoutManager
-import org.oppia.app.application.ApplicationContext
 import org.oppia.app.databinding.TopicTrainFragmentBinding
 import org.oppia.app.fragment.FragmentScope
 import org.oppia.app.model.SkillSummary
@@ -26,13 +24,12 @@ import javax.inject.Inject
 /** The presenter for [TopicTrainFragment]. */
 @FragmentScope
 class TopicTrainFragmentPresenter @Inject constructor(
-  @ApplicationContext private val context: Context,
   private val fragment: Fragment,
   private val logger: Logger,
   private val topicController: TopicController,
   private val viewModelProvider: ViewModelProvider<TopicTrainViewModel>
 ) : SkillSelector {
-  val selectedSkillList = ArrayList<SkillSummary>()
+  private val selectedSkillList = ArrayList<SkillSummary>()
 
   fun handleCreateView(inflater: LayoutInflater, container: ViewGroup?): View? {
     val binding = TopicTrainFragmentBinding.inflate(inflater, container, /* attachToRoot= */ false)
@@ -86,14 +83,14 @@ class TopicTrainFragmentPresenter @Inject constructor(
     getTopicTrainViewModel().selectedSkillList(selectedSkillList)
   }
 
-  fun startButtonClicked(v: View) {
+  fun startQuestionPlayer() {
     val skillList = selectedSkillList
     val skillIdList = ArrayList<String>()
     for (skill in skillList) {
       skillIdList.add(skill.skillId)
     }
-    val questionPlayerIntent = Intent(context, QuestionPlayerActivity::class.java)
+    val questionPlayerIntent = Intent(fragment.context, QuestionPlayerActivity::class.java)
     questionPlayerIntent.putStringArrayListExtra("SKILL_ID_LIST", skillIdList)
-    context.startActivity(questionPlayerIntent)
+    fragment.context!!.startActivity(questionPlayerIntent)
   }
 }
diff --git a/app/src/main/java/org/oppia/app/topic/train/TopicTrainViewModel.kt b/app/src/main/java/org/oppia/app/topic/train/TopicTrainViewModel.kt
index a1e5f9e9876..c69bc18dd6c 100644
--- a/app/src/main/java/org/oppia/app/topic/train/TopicTrainViewModel.kt
+++ b/app/src/main/java/org/oppia/app/topic/train/TopicTrainViewModel.kt
@@ -1,5 +1,6 @@
 package org.oppia.app.topic.train
 
+import android.view.View
 import androidx.databinding.ObservableField
 import androidx.lifecycle.ViewModel
 import org.oppia.app.fragment.FragmentScope
@@ -8,10 +9,17 @@ import javax.inject.Inject
 
 /** [ViewModel] for showing skills in train fragment. */
 @FragmentScope
-class TopicTrainViewModel @Inject constructor() : ViewModel() {
+class TopicTrainViewModel @Inject constructor(
+  private val topicTrainFragmentPresenter: TopicTrainFragmentPresenter
+) : ViewModel() {
+
   var isSubmitButtonActive = ObservableField<Boolean>(false)
 
   fun selectedSkillList(selectedSkillList: ArrayList<SkillSummary>) {
     isSubmitButtonActive.set(selectedSkillList.isNotEmpty())
   }
+
+  fun startButtonClicked(v: View) {
+    topicTrainFragmentPresenter.startQuestionPlayer()
+  }
 }
diff --git a/app/src/main/res/layout/topic_train_fragment.xml b/app/src/main/res/layout/topic_train_fragment.xml
index 50d34d69427..d09ed6151fe 100644
--- a/app/src/main/res/layout/topic_train_fragment.xml
+++ b/app/src/main/res/layout/topic_train_fragment.xml
@@ -56,7 +56,7 @@
           android:layout_marginTop="24dp"
           android:background="@{viewModel.isSubmitButtonActive() ? @drawable/state_button_primary_background :@drawable/state_button_transparent_background}"
           android:clickable="@{viewModel.isSubmitButtonActive()}"
-          android:onClick="@{presenter::startButtonClicked}"
+          android:onClick="@{viewModel::startButtonClicked}"
           android:text="@string/topic_train_start"
           android:textColor="@{viewModel.isSubmitButtonActive()? @color/white : @color/submitButtonInactive}"/>
       </LinearLayout>

From e30e58a01a8db7d63f49f9f6f46b9c52298f6c1b Mon Sep 17 00:00:00 2001
From: Rajat Talesra <talesra@talesra-macbookpro.roam.corp.google.com>
Date: Sat, 5 Oct 2019 15:52:43 +0530
Subject: [PATCH 07/28] Start button activated

---
 app/src/main/res/values/styles.xml | 1 +
 1 file changed, 1 insertion(+)

diff --git a/app/src/main/res/values/styles.xml b/app/src/main/res/values/styles.xml
index b36413eb4a9..c92ae2e725e 100644
--- a/app/src/main/res/values/styles.xml
+++ b/app/src/main/res/values/styles.xml
@@ -68,5 +68,6 @@
     <item name="android:background">@android:color/transparent</item>
     <item name="android:textColor">#56000000</item>
     <item name="android:textSize">14sp</item>
+    <item name="android:clickable">false</item>
   </style>
 </resources>

From b1cef8220f96118115c3c24779f6bbebaea98cd2 Mon Sep 17 00:00:00 2001
From: Rajat Talesra <talesra@talesra-macbookpro.roam.corp.google.com>
Date: Sat, 5 Oct 2019 21:07:42 +0530
Subject: [PATCH 08/28] Separate ViewModel for item

---
 .../app/topic/train/SkillSelectionAdapter.kt  | 41 ++++++++++---------
 .../train/TopicTrainFragmentPresenter.kt      | 10 ++++-
 .../res/layout/topic_train_skill_view.xml     |  2 +-
 3 files changed, 30 insertions(+), 23 deletions(-)

diff --git a/app/src/main/java/org/oppia/app/topic/train/SkillSelectionAdapter.kt b/app/src/main/java/org/oppia/app/topic/train/SkillSelectionAdapter.kt
index 57c30f539cd..bc3a2384007 100644
--- a/app/src/main/java/org/oppia/app/topic/train/SkillSelectionAdapter.kt
+++ b/app/src/main/java/org/oppia/app/topic/train/SkillSelectionAdapter.kt
@@ -1,9 +1,8 @@
-package org.oppia.app.topic.train;
+package org.oppia.app.topic.train
 
 import android.view.LayoutInflater
 import android.view.ViewGroup
 import androidx.databinding.DataBindingUtil
-import androidx.databinding.ViewDataBinding
 import androidx.databinding.library.baseAdapters.BR
 import androidx.recyclerview.widget.RecyclerView
 import kotlinx.android.synthetic.main.topic_train_skill_view.view.*
@@ -13,32 +12,34 @@ import org.oppia.app.model.SkillSummary
 
 // TODO(#172): Make use of generic data-binding-enabled RecyclerView adapter.
 /** Adapter to bind skills to [RecyclerView] inside [TopicTrainFragment]. */
-class SkillSelectionAdapter(
-  private val skillList: List<SkillSummary>,
-  private val skillSelector: SkillSelector
-) : RecyclerView.Adapter<RecyclerView.ViewHolder>() {
-
-  override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): RecyclerView.ViewHolder {
-    val inflater = LayoutInflater.from(parent.context)
-    val binding =
-      DataBindingUtil.inflate<TopicTrainSkillViewBinding>(
-        inflater,
-        R.layout.topic_train_skill_view,
-        parent,
-        /* attachToParent= */false
-      )
-    return SkillViewHolder(binding)
+class SkillSelectionAdapter(private val skillSelector: SkillSelector) :
+  RecyclerView.Adapter<SkillSelectionAdapter.SkillViewHolder>() {
+
+  private var skillList: List<SkillSummary> = ArrayList()
+
+  override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): SkillViewHolder {
+    val skillListItemBinding = DataBindingUtil.inflate<TopicTrainSkillViewBinding>(
+      LayoutInflater.from(parent.context),
+      R.layout.topic_train_skill_view, parent, false
+    )
+    return SkillViewHolder(skillListItemBinding)
   }
 
-  override fun onBindViewHolder(holder: RecyclerView.ViewHolder, position: Int) {
-    (holder as SkillViewHolder).bind(skillList[position], position)
+  override fun onBindViewHolder(skillViewHolder: SkillViewHolder, i: Int) {
+    val skill = skillList[i]
+    skillViewHolder.bind(skill, i)
   }
 
   override fun getItemCount(): Int {
     return skillList.size
   }
 
-  private inner class SkillViewHolder(val binding: ViewDataBinding) : RecyclerView.ViewHolder(binding.root) {
+  fun setSkillList(skillList: List<SkillSummary>) {
+    this.skillList = skillList
+    notifyDataSetChanged()
+  }
+
+  inner class SkillViewHolder(val binding: TopicTrainSkillViewBinding) : RecyclerView.ViewHolder(binding.root) {
     internal fun bind(rawString: SkillSummary, position: Int) {
       binding.setVariable(BR.skill, rawString)
       binding.root.skill_check_box.setOnCheckedChangeListener { buttonView, isChecked ->
diff --git a/app/src/main/java/org/oppia/app/topic/train/TopicTrainFragmentPresenter.kt b/app/src/main/java/org/oppia/app/topic/train/TopicTrainFragmentPresenter.kt
index 29b8441a842..55983ffad9e 100644
--- a/app/src/main/java/org/oppia/app/topic/train/TopicTrainFragmentPresenter.kt
+++ b/app/src/main/java/org/oppia/app/topic/train/TopicTrainFragmentPresenter.kt
@@ -31,10 +31,15 @@ class TopicTrainFragmentPresenter @Inject constructor(
 ) : SkillSelector {
   private val selectedSkillList = ArrayList<SkillSummary>()
 
+  private lateinit var skillSelectionAdapter: SkillSelectionAdapter
+
   fun handleCreateView(inflater: LayoutInflater, container: ViewGroup?): View? {
     val binding = TopicTrainFragmentBinding.inflate(inflater, container, /* attachToRoot= */ false)
+
+    skillSelectionAdapter = SkillSelectionAdapter(this)
     binding.skillRecyclerView.apply {
       layoutManager = LinearLayoutManager(context)
+      adapter = skillSelectionAdapter
     }
     binding.let {
       it.viewModel = getTopicTrainViewModel()
@@ -51,8 +56,9 @@ class TopicTrainFragmentPresenter @Inject constructor(
 
   private fun getSkillList(binding: TopicTrainFragmentBinding) {
     topicLiveData.observe(fragment, Observer<Topic> { result ->
-      val skillAdapter = SkillSelectionAdapter(result.skillList, this)
-      binding.skillRecyclerView.adapter = skillAdapter
+      skillSelectionAdapter.setSkillList(result.skillList)
+      //val skillSelectionAdapter = SkillSelectionAdapter(result.skillList, this)
+      //binding.skillRecyclerView.adapter = skillSelectionAdapter
     })
   }
 
diff --git a/app/src/main/res/layout/topic_train_skill_view.xml b/app/src/main/res/layout/topic_train_skill_view.xml
index b25416135f2..cad5d95786f 100644
--- a/app/src/main/res/layout/topic_train_skill_view.xml
+++ b/app/src/main/res/layout/topic_train_skill_view.xml
@@ -5,7 +5,7 @@
   <data>
     <variable
       name="skill"
-      type="org.oppia.app.model.SkillSummaryOrBuilder"/>
+      type="org.oppia.app.model.SkillSummary"/>
   </data>
   <androidx.constraintlayout.widget.ConstraintLayout
     android:layout_width="match_parent"

From 23e4d27995c26de82bd0657fa261a3dd0f24ebac Mon Sep 17 00:00:00 2001
From: Rajat Talesra <talesra@talesra-macbookpro.roam.corp.google.com>
Date: Sat, 5 Oct 2019 23:56:21 +0530
Subject: [PATCH 09/28] Managing configuration changes

---
 .../app/topic/train/SkillSelectionAdapter.kt  | 21 +++++++-----
 .../oppia/app/topic/train/SkillSelector.kt    |  6 ++--
 .../app/topic/train/TopicTrainFragment.kt     | 18 +++++++---
 .../train/TopicTrainFragmentPresenter.kt      | 33 +++++++++----------
 .../app/topic/train/TopicTrainViewModel.kt    |  3 +-
 5 files changed, 44 insertions(+), 37 deletions(-)

diff --git a/app/src/main/java/org/oppia/app/topic/train/SkillSelectionAdapter.kt b/app/src/main/java/org/oppia/app/topic/train/SkillSelectionAdapter.kt
index bc3a2384007..2490910c546 100644
--- a/app/src/main/java/org/oppia/app/topic/train/SkillSelectionAdapter.kt
+++ b/app/src/main/java/org/oppia/app/topic/train/SkillSelectionAdapter.kt
@@ -16,18 +16,19 @@ class SkillSelectionAdapter(private val skillSelector: SkillSelector) :
   RecyclerView.Adapter<SkillSelectionAdapter.SkillViewHolder>() {
 
   private var skillList: List<SkillSummary> = ArrayList()
+  private var selectedSkillIdList: List<String> = ArrayList()
 
   override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): SkillViewHolder {
     val skillListItemBinding = DataBindingUtil.inflate<TopicTrainSkillViewBinding>(
       LayoutInflater.from(parent.context),
-      R.layout.topic_train_skill_view, parent, false
+      R.layout.topic_train_skill_view, parent,
+      /* attachToRoot= */false
     )
     return SkillViewHolder(skillListItemBinding)
   }
 
   override fun onBindViewHolder(skillViewHolder: SkillViewHolder, i: Int) {
-    val skill = skillList[i]
-    skillViewHolder.bind(skill, i)
+    skillViewHolder.bind(skillList[i], i)
   }
 
   override fun getItemCount(): Int {
@@ -39,15 +40,19 @@ class SkillSelectionAdapter(private val skillSelector: SkillSelector) :
     notifyDataSetChanged()
   }
 
+  fun setSelectedSkillList(skillIdList: ArrayList<String>) {
+    selectedSkillIdList = skillIdList
+  }
+
   inner class SkillViewHolder(val binding: TopicTrainSkillViewBinding) : RecyclerView.ViewHolder(binding.root) {
-    internal fun bind(rawString: SkillSummary, position: Int) {
-      binding.setVariable(BR.skill, rawString)
+    internal fun bind(skill: SkillSummary, position: Int) {
+      binding.setVariable(BR.skill, skill)
+      binding.root.skill_check_box.isChecked = selectedSkillIdList.contains(skill.skillId)
       binding.root.skill_check_box.setOnCheckedChangeListener { buttonView, isChecked ->
-        val skill = skillList[position]
         if (isChecked) {
-          skillSelector.skillSelected(skill)
+          skillSelector.skillSelected(skill.skillId)
         } else {
-          skillSelector.skillUnselected(skill)
+          skillSelector.skillUnselected(skill.skillId)
         }
       }
     }
diff --git a/app/src/main/java/org/oppia/app/topic/train/SkillSelector.kt b/app/src/main/java/org/oppia/app/topic/train/SkillSelector.kt
index 00cc51efd86..6cdc24442a4 100644
--- a/app/src/main/java/org/oppia/app/topic/train/SkillSelector.kt
+++ b/app/src/main/java/org/oppia/app/topic/train/SkillSelector.kt
@@ -1,11 +1,9 @@
 package org.oppia.app.topic.train
 
-import org.oppia.app.model.SkillSummary
-
 /** Interface to update the selectedSkillList in [TopicTrainFragmentPresenter]. */
 interface SkillSelector {
   /** This skill will get added to selectedSkillList in [TopicTrainFragmentPresenter]. */
-  fun skillSelected(skill: SkillSummary)
+  fun skillSelected(skillId: String)
   /** This skill will get removed from selectedSkillList in [TopicTrainFragmentPresenter]. */
-  fun skillUnselected(skill: SkillSummary)
+  fun skillUnselected(skillId: String)
 }
diff --git a/app/src/main/java/org/oppia/app/topic/train/TopicTrainFragment.kt b/app/src/main/java/org/oppia/app/topic/train/TopicTrainFragment.kt
index bfa26bef8ef..60192ccfec5 100644
--- a/app/src/main/java/org/oppia/app/topic/train/TopicTrainFragment.kt
+++ b/app/src/main/java/org/oppia/app/topic/train/TopicTrainFragment.kt
@@ -1,17 +1,16 @@
 package org.oppia.app.topic.train
 
 import android.content.Context
-import android.content.Intent
 import android.os.Bundle
-import android.util.Log
 import android.view.LayoutInflater
 import android.view.View
 import android.view.ViewGroup
 import org.oppia.app.fragment.InjectableFragment
-import org.oppia.app.topic.questionplayer.QuestionPlayerActivity
 import javax.inject.Inject
 
-/** Fragment that contains skills for topic train mode. */
+private const val KEY_SKILL_ID_LIST = "SKILL_ID_LIST"
+
+/** Fragment that displays skills for topic train mode. */
 class TopicTrainFragment : InjectableFragment() {
   @Inject
   lateinit var topicTrainFragmentPresenter: TopicTrainFragmentPresenter
@@ -22,6 +21,15 @@ class TopicTrainFragment : InjectableFragment() {
   }
 
   override fun onCreateView(inflater: LayoutInflater, container: ViewGroup?, savedInstanceState: Bundle?): View? {
-    return topicTrainFragmentPresenter.handleCreateView(inflater, container)
+    var selectedIdList = ArrayList<String>()
+    if (savedInstanceState != null) {
+      selectedIdList = savedInstanceState.getStringArrayList(KEY_SKILL_ID_LIST)
+    }
+    return topicTrainFragmentPresenter.handleCreateView(inflater, container, selectedIdList)
+  }
+
+  override fun onSaveInstanceState(outState: Bundle) {
+    super.onSaveInstanceState(outState)
+    outState.putStringArrayList(KEY_SKILL_ID_LIST, topicTrainFragmentPresenter.selectedSkillList)
   }
 }
diff --git a/app/src/main/java/org/oppia/app/topic/train/TopicTrainFragmentPresenter.kt b/app/src/main/java/org/oppia/app/topic/train/TopicTrainFragmentPresenter.kt
index 55983ffad9e..57362cf1d52 100644
--- a/app/src/main/java/org/oppia/app/topic/train/TopicTrainFragmentPresenter.kt
+++ b/app/src/main/java/org/oppia/app/topic/train/TopicTrainFragmentPresenter.kt
@@ -11,7 +11,6 @@ import androidx.lifecycle.Transformations
 import androidx.recyclerview.widget.LinearLayoutManager
 import org.oppia.app.databinding.TopicTrainFragmentBinding
 import org.oppia.app.fragment.FragmentScope
-import org.oppia.app.model.SkillSummary
 import org.oppia.app.model.Topic
 import org.oppia.app.topic.questionplayer.QuestionPlayerActivity
 import org.oppia.app.viewmodel.ViewModelProvider
@@ -29,11 +28,12 @@ class TopicTrainFragmentPresenter @Inject constructor(
   private val topicController: TopicController,
   private val viewModelProvider: ViewModelProvider<TopicTrainViewModel>
 ) : SkillSelector {
-  private val selectedSkillList = ArrayList<SkillSummary>()
+  lateinit var selectedSkillList: ArrayList<String>
 
   private lateinit var skillSelectionAdapter: SkillSelectionAdapter
 
-  fun handleCreateView(inflater: LayoutInflater, container: ViewGroup?): View? {
+  fun handleCreateView(inflater: LayoutInflater, container: ViewGroup?, skillList : ArrayList<String>): View? {
+    selectedSkillList = skillList
     val binding = TopicTrainFragmentBinding.inflate(inflater, container, /* attachToRoot= */ false)
 
     skillSelectionAdapter = SkillSelectionAdapter(this)
@@ -45,32 +45,34 @@ class TopicTrainFragmentPresenter @Inject constructor(
       it.viewModel = getTopicTrainViewModel()
       it.lifecycleOwner = fragment
     }
-    getSkillList(binding)
+    getSkillList()
     return binding.root
   }
 
+  private val topicLiveData: LiveData<Topic> by lazy { getTopicList() }
+
   // TODO(#135): Get this topic-id or get skillList from from [TopicFragment].
   private val topicResultLiveData: LiveData<AsyncResult<Topic>> by lazy {
     topicController.getTopic(TEST_TOPIC_ID_0)
   }
 
-  private fun getSkillList(binding: TopicTrainFragmentBinding) {
+  private fun getSkillList() {
     topicLiveData.observe(fragment, Observer<Topic> { result ->
       skillSelectionAdapter.setSkillList(result.skillList)
-      //val skillSelectionAdapter = SkillSelectionAdapter(result.skillList, this)
-      //binding.skillRecyclerView.adapter = skillSelectionAdapter
+      if(selectedSkillList.isNotEmpty()) {
+        skillSelectionAdapter.setSelectedSkillList(selectedSkillList)
+        getTopicTrainViewModel().selectedSkillList(selectedSkillList)
+      }
     })
   }
 
-  private val topicLiveData: LiveData<Topic> by lazy { getTopicList() }
-
   private fun getTopicList(): LiveData<Topic> {
     return Transformations.map(topicResultLiveData, ::processTopicResult)
   }
 
   private fun processTopicResult(topic: AsyncResult<Topic>): Topic {
     if (topic.isFailure()) {
-      logger.e("TopicTrainFragmentPresenter", "Failed to retrieve ephemeral state ${topic.getErrorOrNull()}")
+      logger.e("TopicTrainFragmentPresenter", "Failed to retrieve topic ${topic.getErrorOrNull()}")
     }
     return topic.getOrDefault(Topic.getDefaultInstance())
   }
@@ -79,24 +81,19 @@ class TopicTrainFragmentPresenter @Inject constructor(
     return viewModelProvider.getForFragment(fragment, TopicTrainViewModel::class.java)
   }
 
-  override fun skillSelected(skill: SkillSummary) {
+  override fun skillSelected(skill: String) {
     selectedSkillList.add(skill)
     getTopicTrainViewModel().selectedSkillList(selectedSkillList)
   }
 
-  override fun skillUnselected(skill: SkillSummary) {
+  override fun skillUnselected(skill: String) {
     selectedSkillList.remove(skill)
     getTopicTrainViewModel().selectedSkillList(selectedSkillList)
   }
 
   fun startQuestionPlayer() {
-    val skillList = selectedSkillList
-    val skillIdList = ArrayList<String>()
-    for (skill in skillList) {
-      skillIdList.add(skill.skillId)
-    }
     val questionPlayerIntent = Intent(fragment.context, QuestionPlayerActivity::class.java)
-    questionPlayerIntent.putStringArrayListExtra("SKILL_ID_LIST", skillIdList)
+    questionPlayerIntent.putStringArrayListExtra("SKILL_ID_LIST", selectedSkillList)
     fragment.context!!.startActivity(questionPlayerIntent)
   }
 }
diff --git a/app/src/main/java/org/oppia/app/topic/train/TopicTrainViewModel.kt b/app/src/main/java/org/oppia/app/topic/train/TopicTrainViewModel.kt
index c69bc18dd6c..c7c87de4ece 100644
--- a/app/src/main/java/org/oppia/app/topic/train/TopicTrainViewModel.kt
+++ b/app/src/main/java/org/oppia/app/topic/train/TopicTrainViewModel.kt
@@ -4,7 +4,6 @@ import android.view.View
 import androidx.databinding.ObservableField
 import androidx.lifecycle.ViewModel
 import org.oppia.app.fragment.FragmentScope
-import org.oppia.app.model.SkillSummary
 import javax.inject.Inject
 
 /** [ViewModel] for showing skills in train fragment. */
@@ -15,7 +14,7 @@ class TopicTrainViewModel @Inject constructor(
 
   var isSubmitButtonActive = ObservableField<Boolean>(false)
 
-  fun selectedSkillList(selectedSkillList: ArrayList<SkillSummary>) {
+  fun selectedSkillList(selectedSkillList: ArrayList<String>) {
     isSubmitButtonActive.set(selectedSkillList.isNotEmpty())
   }
 

From 7fe1f87b6d62a6024f167e3e078258062639af75 Mon Sep 17 00:00:00 2001
From: Rajat Talesra <talesra@talesra-macbookpro.roam.corp.google.com>
Date: Sun, 6 Oct 2019 00:39:51 +0530
Subject: [PATCH 10/28] Checkbox state save

---
 .../app/topic/train/SkillSelectionAdapter.kt  |  4 ++--
 .../app/topic/train/TopicTrainFragment.kt     |  2 +-
 .../train/TopicTrainFragmentPresenter.kt      | 23 ++++++++-----------
 .../res/layout/topic_train_skill_view.xml     |  4 ++++
 4 files changed, 17 insertions(+), 16 deletions(-)

diff --git a/app/src/main/java/org/oppia/app/topic/train/SkillSelectionAdapter.kt b/app/src/main/java/org/oppia/app/topic/train/SkillSelectionAdapter.kt
index 2490910c546..f3e9527e8f1 100644
--- a/app/src/main/java/org/oppia/app/topic/train/SkillSelectionAdapter.kt
+++ b/app/src/main/java/org/oppia/app/topic/train/SkillSelectionAdapter.kt
@@ -16,7 +16,7 @@ class SkillSelectionAdapter(private val skillSelector: SkillSelector) :
   RecyclerView.Adapter<SkillSelectionAdapter.SkillViewHolder>() {
 
   private var skillList: List<SkillSummary> = ArrayList()
-  private var selectedSkillIdList: List<String> = ArrayList()
+  private var selectedSkillIdList: ArrayList<String> = ArrayList()
 
   override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): SkillViewHolder {
     val skillListItemBinding = DataBindingUtil.inflate<TopicTrainSkillViewBinding>(
@@ -46,8 +46,8 @@ class SkillSelectionAdapter(private val skillSelector: SkillSelector) :
 
   inner class SkillViewHolder(val binding: TopicTrainSkillViewBinding) : RecyclerView.ViewHolder(binding.root) {
     internal fun bind(skill: SkillSummary, position: Int) {
+      binding.setVariable(BR.isChecked, selectedSkillIdList.contains(skill.skillId))
       binding.setVariable(BR.skill, skill)
-      binding.root.skill_check_box.isChecked = selectedSkillIdList.contains(skill.skillId)
       binding.root.skill_check_box.setOnCheckedChangeListener { buttonView, isChecked ->
         if (isChecked) {
           skillSelector.skillSelected(skill.skillId)
diff --git a/app/src/main/java/org/oppia/app/topic/train/TopicTrainFragment.kt b/app/src/main/java/org/oppia/app/topic/train/TopicTrainFragment.kt
index 60192ccfec5..dde27acf032 100644
--- a/app/src/main/java/org/oppia/app/topic/train/TopicTrainFragment.kt
+++ b/app/src/main/java/org/oppia/app/topic/train/TopicTrainFragment.kt
@@ -30,6 +30,6 @@ class TopicTrainFragment : InjectableFragment() {
 
   override fun onSaveInstanceState(outState: Bundle) {
     super.onSaveInstanceState(outState)
-    outState.putStringArrayList(KEY_SKILL_ID_LIST, topicTrainFragmentPresenter.selectedSkillList)
+    outState.putStringArrayList(KEY_SKILL_ID_LIST, topicTrainFragmentPresenter.selectedSkillIdList)
   }
 }
diff --git a/app/src/main/java/org/oppia/app/topic/train/TopicTrainFragmentPresenter.kt b/app/src/main/java/org/oppia/app/topic/train/TopicTrainFragmentPresenter.kt
index 57362cf1d52..c537d9ee39c 100644
--- a/app/src/main/java/org/oppia/app/topic/train/TopicTrainFragmentPresenter.kt
+++ b/app/src/main/java/org/oppia/app/topic/train/TopicTrainFragmentPresenter.kt
@@ -28,12 +28,12 @@ class TopicTrainFragmentPresenter @Inject constructor(
   private val topicController: TopicController,
   private val viewModelProvider: ViewModelProvider<TopicTrainViewModel>
 ) : SkillSelector {
-  lateinit var selectedSkillList: ArrayList<String>
+  lateinit var selectedSkillIdList: ArrayList<String>
 
   private lateinit var skillSelectionAdapter: SkillSelectionAdapter
 
   fun handleCreateView(inflater: LayoutInflater, container: ViewGroup?, skillList : ArrayList<String>): View? {
-    selectedSkillList = skillList
+    selectedSkillIdList = skillList
     val binding = TopicTrainFragmentBinding.inflate(inflater, container, /* attachToRoot= */ false)
 
     skillSelectionAdapter = SkillSelectionAdapter(this)
@@ -59,10 +59,7 @@ class TopicTrainFragmentPresenter @Inject constructor(
   private fun getSkillList() {
     topicLiveData.observe(fragment, Observer<Topic> { result ->
       skillSelectionAdapter.setSkillList(result.skillList)
-      if(selectedSkillList.isNotEmpty()) {
-        skillSelectionAdapter.setSelectedSkillList(selectedSkillList)
-        getTopicTrainViewModel().selectedSkillList(selectedSkillList)
-      }
+      skillSelectionAdapter.setSelectedSkillList(selectedSkillIdList)
     })
   }
 
@@ -81,19 +78,19 @@ class TopicTrainFragmentPresenter @Inject constructor(
     return viewModelProvider.getForFragment(fragment, TopicTrainViewModel::class.java)
   }
 
-  override fun skillSelected(skill: String) {
-    selectedSkillList.add(skill)
-    getTopicTrainViewModel().selectedSkillList(selectedSkillList)
+  override fun skillSelected(skillId: String) {
+    selectedSkillIdList.add(skillId)
+    getTopicTrainViewModel().selectedSkillList(selectedSkillIdList)
   }
 
-  override fun skillUnselected(skill: String) {
-    selectedSkillList.remove(skill)
-    getTopicTrainViewModel().selectedSkillList(selectedSkillList)
+  override fun skillUnselected(skillId: String) {
+    selectedSkillIdList.remove(skillId)
+    getTopicTrainViewModel().selectedSkillList(selectedSkillIdList)
   }
 
   fun startQuestionPlayer() {
     val questionPlayerIntent = Intent(fragment.context, QuestionPlayerActivity::class.java)
-    questionPlayerIntent.putStringArrayListExtra("SKILL_ID_LIST", selectedSkillList)
+    questionPlayerIntent.putStringArrayListExtra("SKILL_ID_LIST", selectedSkillIdList)
     fragment.context!!.startActivity(questionPlayerIntent)
   }
 }
diff --git a/app/src/main/res/layout/topic_train_skill_view.xml b/app/src/main/res/layout/topic_train_skill_view.xml
index cad5d95786f..a9968e57f19 100644
--- a/app/src/main/res/layout/topic_train_skill_view.xml
+++ b/app/src/main/res/layout/topic_train_skill_view.xml
@@ -3,6 +3,9 @@
   xmlns:android="http://schemas.android.com/apk/res/android"
   xmlns:app="http://schemas.android.com/apk/res-auto">
   <data>
+    <variable
+      name="isChecked"
+      type="Boolean"/>
     <variable
       name="skill"
       type="org.oppia.app.model.SkillSummary"/>
@@ -15,6 +18,7 @@
       android:layout_width="match_parent"
       android:layout_height="wrap_content"
       android:layout_margin="4dp"
+      android:checked="@{isChecked}"
       android:drawablePadding="4dp"
       android:gravity="center_vertical"
       android:text="@{skill.description}"

From 3d0315a52f1600dd688c8535251b17e78043b4df Mon Sep 17 00:00:00 2001
From: Rajat Talesra <talesra@talesra-macbookpro.roam.corp.google.com>
Date: Sun, 6 Oct 2019 00:54:23 +0530
Subject: [PATCH 11/28] Nit changes

---
 .../org/oppia/app/topic/train/TopicTrainFragmentPresenter.kt    | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/app/src/main/java/org/oppia/app/topic/train/TopicTrainFragmentPresenter.kt b/app/src/main/java/org/oppia/app/topic/train/TopicTrainFragmentPresenter.kt
index c537d9ee39c..b5eba4f8163 100644
--- a/app/src/main/java/org/oppia/app/topic/train/TopicTrainFragmentPresenter.kt
+++ b/app/src/main/java/org/oppia/app/topic/train/TopicTrainFragmentPresenter.kt
@@ -51,7 +51,7 @@ class TopicTrainFragmentPresenter @Inject constructor(
 
   private val topicLiveData: LiveData<Topic> by lazy { getTopicList() }
 
-  // TODO(#135): Get this topic-id or get skillList from from [TopicFragment].
+  // TODO(#135): Get this topic-id or get skillList from [TopicFragment].
   private val topicResultLiveData: LiveData<AsyncResult<Topic>> by lazy {
     topicController.getTopic(TEST_TOPIC_ID_0)
   }

From 6c5387ffdcc9c9848b529fe0ce9ad0785dd8b188 Mon Sep 17 00:00:00 2001
From: Rajat Talesra <talesra@talesra-macbookpro.roam.corp.google.com>
Date: Sun, 6 Oct 2019 14:47:00 +0530
Subject: [PATCH 12/28] Fixing HomeActivityController

---
 .../org/oppia/app/home/HomeActivityController.kt  | 15 +++++++++++----
 1 file changed, 11 insertions(+), 4 deletions(-)

diff --git a/app/src/main/java/org/oppia/app/home/HomeActivityController.kt b/app/src/main/java/org/oppia/app/home/HomeActivityController.kt
index 9fd3b0e7f81..c4ea78ec150 100644
--- a/app/src/main/java/org/oppia/app/home/HomeActivityController.kt
+++ b/app/src/main/java/org/oppia/app/home/HomeActivityController.kt
@@ -3,6 +3,7 @@ package org.oppia.app.home
 import androidx.appcompat.app.AppCompatActivity
 import org.oppia.app.R
 import org.oppia.app.activity.ActivityScope
+import org.oppia.app.topic.train.TopicTrainFragment
 import javax.inject.Inject
 
 /** The controller for [HomeActivity]. */
@@ -10,9 +11,15 @@ import javax.inject.Inject
 class HomeActivityController @Inject constructor(private val activity: AppCompatActivity) {
   fun handleOnCreate() {
     activity.setContentView(R.layout.home_activity)
-    activity.supportFragmentManager.beginTransaction().add(
-      R.id.home_fragment_placeholder,
-      HomeFragment()
-    ).commitNow()
+    if (getHomeFragment() == null) {
+      activity.supportFragmentManager.beginTransaction().add(
+        R.id.home_fragment_placeholder,
+        HomeFragment()
+      ).commitNow()
+    }
+  }
+
+  private fun getHomeFragment(): HomeFragment? {
+    return activity.supportFragmentManager.findFragmentById(R.id.home_fragment_placeholder) as HomeFragment?
   }
 }

From 5b2dc90b2e45eed2cb4dcf73cf61a07dce951d6b Mon Sep 17 00:00:00 2001
From: Rajat Talesra <talesra@talesra-macbookpro.roam.corp.google.com>
Date: Sun, 6 Oct 2019 16:28:08 +0530
Subject: [PATCH 13/28] Managing configuration change in checkboxes

---
 .../org/oppia/app/home/HomeActivityController.kt |  1 -
 .../app/topic/train/SkillSelectionAdapter.kt     |  1 +
 .../topic/train/TopicTrainFragmentPresenter.kt   | 16 ++++++++++++----
 .../oppia/app/topic/train/TopicTrainViewModel.kt |  2 ++
 4 files changed, 15 insertions(+), 5 deletions(-)

diff --git a/app/src/main/java/org/oppia/app/home/HomeActivityController.kt b/app/src/main/java/org/oppia/app/home/HomeActivityController.kt
index c4ea78ec150..3b8188d7b09 100644
--- a/app/src/main/java/org/oppia/app/home/HomeActivityController.kt
+++ b/app/src/main/java/org/oppia/app/home/HomeActivityController.kt
@@ -3,7 +3,6 @@ package org.oppia.app.home
 import androidx.appcompat.app.AppCompatActivity
 import org.oppia.app.R
 import org.oppia.app.activity.ActivityScope
-import org.oppia.app.topic.train.TopicTrainFragment
 import javax.inject.Inject
 
 /** The controller for [HomeActivity]. */
diff --git a/app/src/main/java/org/oppia/app/topic/train/SkillSelectionAdapter.kt b/app/src/main/java/org/oppia/app/topic/train/SkillSelectionAdapter.kt
index f3e9527e8f1..36e09f14b11 100644
--- a/app/src/main/java/org/oppia/app/topic/train/SkillSelectionAdapter.kt
+++ b/app/src/main/java/org/oppia/app/topic/train/SkillSelectionAdapter.kt
@@ -1,5 +1,6 @@
 package org.oppia.app.topic.train
 
+import android.util.Log
 import android.view.LayoutInflater
 import android.view.ViewGroup
 import androidx.databinding.DataBindingUtil
diff --git a/app/src/main/java/org/oppia/app/topic/train/TopicTrainFragmentPresenter.kt b/app/src/main/java/org/oppia/app/topic/train/TopicTrainFragmentPresenter.kt
index b5eba4f8163..2cc2daed0c8 100644
--- a/app/src/main/java/org/oppia/app/topic/train/TopicTrainFragmentPresenter.kt
+++ b/app/src/main/java/org/oppia/app/topic/train/TopicTrainFragmentPresenter.kt
@@ -1,5 +1,6 @@
 package org.oppia.app.topic.train
 
+import android.content.Context
 import android.content.Intent
 import android.view.LayoutInflater
 import android.view.View
@@ -9,6 +10,7 @@ import androidx.lifecycle.LiveData
 import androidx.lifecycle.Observer
 import androidx.lifecycle.Transformations
 import androidx.recyclerview.widget.LinearLayoutManager
+import org.oppia.app.application.ApplicationContext
 import org.oppia.app.databinding.TopicTrainFragmentBinding
 import org.oppia.app.fragment.FragmentScope
 import org.oppia.app.model.Topic
@@ -23,6 +25,7 @@ import javax.inject.Inject
 /** The presenter for [TopicTrainFragment]. */
 @FragmentScope
 class TopicTrainFragmentPresenter @Inject constructor(
+  @ApplicationContext private val context: Context,
   private val fragment: Fragment,
   private val logger: Logger,
   private val topicController: TopicController,
@@ -79,18 +82,23 @@ class TopicTrainFragmentPresenter @Inject constructor(
   }
 
   override fun skillSelected(skillId: String) {
-    selectedSkillIdList.add(skillId)
+    if(!selectedSkillIdList.contains(skillId)) {
+      selectedSkillIdList.add(skillId)
+    }
     getTopicTrainViewModel().selectedSkillList(selectedSkillIdList)
   }
 
   override fun skillUnselected(skillId: String) {
-    selectedSkillIdList.remove(skillId)
+    if(selectedSkillIdList.contains(skillId)) {
+      selectedSkillIdList.remove(skillId)
+    }
     getTopicTrainViewModel().selectedSkillList(selectedSkillIdList)
   }
 
   fun startQuestionPlayer() {
-    val questionPlayerIntent = Intent(fragment.context, QuestionPlayerActivity::class.java)
+    val questionPlayerIntent = Intent(context, QuestionPlayerActivity::class.java)
     questionPlayerIntent.putStringArrayListExtra("SKILL_ID_LIST", selectedSkillIdList)
-    fragment.context!!.startActivity(questionPlayerIntent)
+    questionPlayerIntent.flags = Intent.FLAG_ACTIVITY_NEW_TASK
+    context.startActivity(questionPlayerIntent)
   }
 }
diff --git a/app/src/main/java/org/oppia/app/topic/train/TopicTrainViewModel.kt b/app/src/main/java/org/oppia/app/topic/train/TopicTrainViewModel.kt
index c7c87de4ece..cff248324e9 100644
--- a/app/src/main/java/org/oppia/app/topic/train/TopicTrainViewModel.kt
+++ b/app/src/main/java/org/oppia/app/topic/train/TopicTrainViewModel.kt
@@ -1,5 +1,6 @@
 package org.oppia.app.topic.train
 
+import android.util.Log
 import android.view.View
 import androidx.databinding.ObservableField
 import androidx.lifecycle.ViewModel
@@ -15,6 +16,7 @@ class TopicTrainViewModel @Inject constructor(
   var isSubmitButtonActive = ObservableField<Boolean>(false)
 
   fun selectedSkillList(selectedSkillList: ArrayList<String>) {
+    Log.d("TAG", "Size: "+selectedSkillList.size)
     isSubmitButtonActive.set(selectedSkillList.isNotEmpty())
   }
 

From b9b9683e03e1a86983ff1b5191ae61f6d4d8b08a Mon Sep 17 00:00:00 2001
From: Rajat Talesra <talesra@talesra-macbookpro.roam.corp.google.com>
Date: Sun, 6 Oct 2019 19:58:55 +0530
Subject: [PATCH 14/28] Proper route to QuestionPlayer

---
 .../oppia/app/home/HomeActivityController.kt  | 14 ++++---------
 .../topic/RouteToQuestionPlayerListener.kt    |  6 ++++++
 .../java/org/oppia/app/topic/TopicActivity.kt |  7 ++++++-
 .../oppia/app/topic/TopicActivityPresenter.kt |  7 ++++---
 .../questionplayer/QuestionPlayerActivity.kt  | 20 ++++++++++++-------
 .../train/TopicTrainFragmentPresenter.kt      | 17 +++++++---------
 .../app/topic/train/TopicTrainViewModel.kt    |  2 +-
 7 files changed, 41 insertions(+), 32 deletions(-)
 create mode 100755 app/src/main/java/org/oppia/app/topic/RouteToQuestionPlayerListener.kt

diff --git a/app/src/main/java/org/oppia/app/home/HomeActivityController.kt b/app/src/main/java/org/oppia/app/home/HomeActivityController.kt
index 3b8188d7b09..9fd3b0e7f81 100644
--- a/app/src/main/java/org/oppia/app/home/HomeActivityController.kt
+++ b/app/src/main/java/org/oppia/app/home/HomeActivityController.kt
@@ -10,15 +10,9 @@ import javax.inject.Inject
 class HomeActivityController @Inject constructor(private val activity: AppCompatActivity) {
   fun handleOnCreate() {
     activity.setContentView(R.layout.home_activity)
-    if (getHomeFragment() == null) {
-      activity.supportFragmentManager.beginTransaction().add(
-        R.id.home_fragment_placeholder,
-        HomeFragment()
-      ).commitNow()
-    }
-  }
-
-  private fun getHomeFragment(): HomeFragment? {
-    return activity.supportFragmentManager.findFragmentById(R.id.home_fragment_placeholder) as HomeFragment?
+    activity.supportFragmentManager.beginTransaction().add(
+      R.id.home_fragment_placeholder,
+      HomeFragment()
+    ).commitNow()
   }
 }
diff --git a/app/src/main/java/org/oppia/app/topic/RouteToQuestionPlayerListener.kt b/app/src/main/java/org/oppia/app/topic/RouteToQuestionPlayerListener.kt
new file mode 100755
index 00000000000..56297cc1405
--- /dev/null
+++ b/app/src/main/java/org/oppia/app/topic/RouteToQuestionPlayerListener.kt
@@ -0,0 +1,6 @@
+package org.oppia.app.topic
+
+/** Listener for when an activity should route to a Question Player. */
+interface RouteToQuestionPlayerListener {
+  fun routeToQuestionPlayer(skillIdList: ArrayList<String>)
+}
diff --git a/app/src/main/java/org/oppia/app/topic/TopicActivity.kt b/app/src/main/java/org/oppia/app/topic/TopicActivity.kt
index 31772522639..ddacb40a12d 100644
--- a/app/src/main/java/org/oppia/app/topic/TopicActivity.kt
+++ b/app/src/main/java/org/oppia/app/topic/TopicActivity.kt
@@ -2,10 +2,11 @@ package org.oppia.app.topic
 
 import android.os.Bundle
 import org.oppia.app.activity.InjectableAppCompatActivity
+import org.oppia.app.topic.questionplayer.QuestionPlayerActivity
 import javax.inject.Inject
 
 /** The activity for tabs in Topic. */
-class TopicActivity : InjectableAppCompatActivity() {
+class TopicActivity : InjectableAppCompatActivity(), RouteToQuestionPlayerListener {
   @Inject lateinit var topicActivityPresenter: TopicActivityPresenter
 
   override fun onCreate(savedInstanceState: Bundle?) {
@@ -13,4 +14,8 @@ class TopicActivity : InjectableAppCompatActivity() {
     activityComponent.inject(this)
     topicActivityPresenter.handleOnCreate()
   }
+
+  override fun routeToQuestionPlayer(skillIdList: ArrayList<String>) {
+    startActivity(QuestionPlayerActivity.createQuestionPlayerActivityIntent(this, skillIdList))
+  }
 }
diff --git a/app/src/main/java/org/oppia/app/topic/TopicActivityPresenter.kt b/app/src/main/java/org/oppia/app/topic/TopicActivityPresenter.kt
index 2e807be8c74..cec58a91b1d 100644
--- a/app/src/main/java/org/oppia/app/topic/TopicActivityPresenter.kt
+++ b/app/src/main/java/org/oppia/app/topic/TopicActivityPresenter.kt
@@ -3,6 +3,7 @@ package org.oppia.app.topic
 import androidx.appcompat.app.AppCompatActivity
 import org.oppia.app.R
 import org.oppia.app.activity.ActivityScope
+import org.oppia.app.topic.train.TopicTrainFragment
 import javax.inject.Inject
 
 /** The presenter for [TopicActivity]. */
@@ -13,12 +14,12 @@ class TopicActivityPresenter @Inject constructor(private val activity: AppCompat
     if (getTopicFragment() == null) {
       activity.supportFragmentManager.beginTransaction().add(
         R.id.topic_fragment_placeholder,
-        TopicFragment()
+        TopicTrainFragment()
       ).commitNow()
     }
   }
 
-  private fun getTopicFragment(): TopicFragment? {
-    return activity.supportFragmentManager.findFragmentById(R.id.topic_fragment_placeholder) as TopicFragment?
+  private fun getTopicFragment(): TopicTrainFragment? {
+    return activity.supportFragmentManager.findFragmentById(R.id.topic_fragment_placeholder) as TopicTrainFragment?
   }
 }
diff --git a/app/src/main/java/org/oppia/app/topic/questionplayer/QuestionPlayerActivity.kt b/app/src/main/java/org/oppia/app/topic/questionplayer/QuestionPlayerActivity.kt
index 0faf20086ca..d506601c5ce 100644
--- a/app/src/main/java/org/oppia/app/topic/questionplayer/QuestionPlayerActivity.kt
+++ b/app/src/main/java/org/oppia/app/topic/questionplayer/QuestionPlayerActivity.kt
@@ -1,10 +1,14 @@
 package org.oppia.app.topic.questionplayer
 
+import android.content.Context
+import android.content.Intent
 import android.os.Bundle
-import android.util.Log
 import org.oppia.app.activity.InjectableAppCompatActivity
+import org.oppia.app.topic.TopicActivity
 import javax.inject.Inject
 
+const val QUESTION_PLAYER_ACTIVITY_SKILL_ID_LIST_ARGUMENT_KEY = "QuestionPlayerActivity.skill_id_list"
+
 /** Activity for QuestionPlayer in train mode. */
 class QuestionPlayerActivity : InjectableAppCompatActivity() {
   @Inject
@@ -14,13 +18,15 @@ class QuestionPlayerActivity : InjectableAppCompatActivity() {
     super.onCreate(savedInstanceState)
     activityComponent.inject(this)
     questionPlayerActivityPresenter.handleOnCreate()
-
-    // TODO(#159): Use this skillList from TopicTrainFragment to fetch questions and start train mode.
-    val skillList: ArrayList<String> = getSkillList()
   }
 
-  private fun getSkillList(): ArrayList<String> {
-    val topicTrainIntent = intent
-    return topicTrainIntent.getStringArrayListExtra("SKILL_ID_LIST")
+  companion object {
+    // TODO(#159): Use this skillList from TopicTrainFragment to fetch questions and start train mode.
+    /** Returns a new [Intent] to route to [TopicActivity] for a specified skill ID list. */
+    fun createQuestionPlayerActivityIntent(context: Context, skillIdList: ArrayList<String>): Intent {
+      val intent = Intent(context, QuestionPlayerActivity::class.java)
+      intent.putExtra(QUESTION_PLAYER_ACTIVITY_SKILL_ID_LIST_ARGUMENT_KEY, skillIdList)
+      return intent
+    }
   }
 }
diff --git a/app/src/main/java/org/oppia/app/topic/train/TopicTrainFragmentPresenter.kt b/app/src/main/java/org/oppia/app/topic/train/TopicTrainFragmentPresenter.kt
index 2cc2daed0c8..4594c2b193b 100644
--- a/app/src/main/java/org/oppia/app/topic/train/TopicTrainFragmentPresenter.kt
+++ b/app/src/main/java/org/oppia/app/topic/train/TopicTrainFragmentPresenter.kt
@@ -1,20 +1,18 @@
 package org.oppia.app.topic.train
 
-import android.content.Context
-import android.content.Intent
 import android.view.LayoutInflater
 import android.view.View
 import android.view.ViewGroup
+import androidx.appcompat.app.AppCompatActivity
 import androidx.fragment.app.Fragment
 import androidx.lifecycle.LiveData
 import androidx.lifecycle.Observer
 import androidx.lifecycle.Transformations
 import androidx.recyclerview.widget.LinearLayoutManager
-import org.oppia.app.application.ApplicationContext
 import org.oppia.app.databinding.TopicTrainFragmentBinding
 import org.oppia.app.fragment.FragmentScope
 import org.oppia.app.model.Topic
-import org.oppia.app.topic.questionplayer.QuestionPlayerActivity
+import org.oppia.app.topic.RouteToQuestionPlayerListener
 import org.oppia.app.viewmodel.ViewModelProvider
 import org.oppia.domain.topic.TEST_TOPIC_ID_0
 import org.oppia.domain.topic.TopicController
@@ -25,7 +23,7 @@ import javax.inject.Inject
 /** The presenter for [TopicTrainFragment]. */
 @FragmentScope
 class TopicTrainFragmentPresenter @Inject constructor(
-  @ApplicationContext private val context: Context,
+  activity: AppCompatActivity,
   private val fragment: Fragment,
   private val logger: Logger,
   private val topicController: TopicController,
@@ -33,6 +31,8 @@ class TopicTrainFragmentPresenter @Inject constructor(
 ) : SkillSelector {
   lateinit var selectedSkillIdList: ArrayList<String>
 
+  private val routeToQuestionPlayerListener = activity as RouteToQuestionPlayerListener
+
   private lateinit var skillSelectionAdapter: SkillSelectionAdapter
 
   fun handleCreateView(inflater: LayoutInflater, container: ViewGroup?, skillList : ArrayList<String>): View? {
@@ -95,10 +95,7 @@ class TopicTrainFragmentPresenter @Inject constructor(
     getTopicTrainViewModel().selectedSkillList(selectedSkillIdList)
   }
 
-  fun startQuestionPlayer() {
-    val questionPlayerIntent = Intent(context, QuestionPlayerActivity::class.java)
-    questionPlayerIntent.putStringArrayListExtra("SKILL_ID_LIST", selectedSkillIdList)
-    questionPlayerIntent.flags = Intent.FLAG_ACTIVITY_NEW_TASK
-    context.startActivity(questionPlayerIntent)
+  fun onStartButtonClicked() {
+    routeToQuestionPlayerListener.routeToQuestionPlayer(selectedSkillIdList)
   }
 }
diff --git a/app/src/main/java/org/oppia/app/topic/train/TopicTrainViewModel.kt b/app/src/main/java/org/oppia/app/topic/train/TopicTrainViewModel.kt
index cff248324e9..216fe9be652 100644
--- a/app/src/main/java/org/oppia/app/topic/train/TopicTrainViewModel.kt
+++ b/app/src/main/java/org/oppia/app/topic/train/TopicTrainViewModel.kt
@@ -21,6 +21,6 @@ class TopicTrainViewModel @Inject constructor(
   }
 
   fun startButtonClicked(v: View) {
-    topicTrainFragmentPresenter.startQuestionPlayer()
+    topicTrainFragmentPresenter.onStartButtonClicked()
   }
 }

From 37a4837929a06acc86867a554e31c5ae41e901b7 Mon Sep 17 00:00:00 2001
From: Rajat Talesra <talesra@talesra-macbookpro.roam.corp.google.com>
Date: Sun, 6 Oct 2019 21:10:44 +0530
Subject: [PATCH 15/28] QuestionPlayerActivity test case

---
 .../org/oppia/app/topic/TopicActivityTest.kt  |  3 +-
 .../QuestionPlayerActivityTest.kt             | 65 +++++++++++++++++++
 2 files changed, 66 insertions(+), 2 deletions(-)
 create mode 100644 app/src/sharedTest/java/org/oppia/app/topic/questionplayer/QuestionPlayerActivityTest.kt

diff --git a/app/src/sharedTest/java/org/oppia/app/topic/TopicActivityTest.kt b/app/src/sharedTest/java/org/oppia/app/topic/TopicActivityTest.kt
index 341b0afbe66..be8a8e8bcaa 100644
--- a/app/src/sharedTest/java/org/oppia/app/topic/TopicActivityTest.kt
+++ b/app/src/sharedTest/java/org/oppia/app/topic/TopicActivityTest.kt
@@ -16,7 +16,6 @@ import kotlinx.coroutines.CoroutineDispatcher
 import org.junit.Test
 import org.junit.runner.RunWith
 import org.oppia.app.R
-import org.oppia.app.player.exploration.ExplorationActivity
 import org.oppia.util.threading.BackgroundDispatcher
 import org.oppia.util.threading.BlockingDispatcher
 import javax.inject.Singleton
@@ -27,7 +26,7 @@ class TopicActivityTest {
 
   @Test
   fun testTopicActivity_loadTopicFragment_hasDummyString() {
-    ActivityScenario.launch(ExplorationActivity::class.java).use {
+    ActivityScenario.launch(TopicActivity::class.java).use {
       onView(withId(R.id.dummy_text_view)).check(matches(withText("This is dummy TextView for testing")))
     }
   }
diff --git a/app/src/sharedTest/java/org/oppia/app/topic/questionplayer/QuestionPlayerActivityTest.kt b/app/src/sharedTest/java/org/oppia/app/topic/questionplayer/QuestionPlayerActivityTest.kt
new file mode 100644
index 00000000000..7bc3c1df511
--- /dev/null
+++ b/app/src/sharedTest/java/org/oppia/app/topic/questionplayer/QuestionPlayerActivityTest.kt
@@ -0,0 +1,65 @@
+package org.oppia.app.topic.questionplayer
+
+import android.app.Application
+import android.content.Context
+import androidx.test.core.app.ActivityScenario
+import androidx.test.espresso.Espresso.onView
+import androidx.test.espresso.assertion.ViewAssertions.matches
+import androidx.test.espresso.matcher.ViewMatchers.withId
+import androidx.test.espresso.matcher.ViewMatchers.withText
+import androidx.test.ext.junit.runners.AndroidJUnit4
+import dagger.BindsInstance
+import dagger.Component
+import dagger.Module
+import dagger.Provides
+import kotlinx.coroutines.CoroutineDispatcher
+import org.junit.Test
+import org.junit.runner.RunWith
+import org.oppia.app.R
+import org.oppia.util.threading.BackgroundDispatcher
+import org.oppia.util.threading.BlockingDispatcher
+import javax.inject.Singleton
+
+/** Tests for [QuestionPlayerActivity]. */
+@RunWith(AndroidJUnit4::class)
+class QuestionPlayerActivityTest {
+
+  @Test
+  fun testQuestionPlayerActivity_loadQuestionPlayerFragment_hasDummyString() {
+    ActivityScenario.launch(QuestionPlayerActivity::class.java).use {
+      onView(withId(R.id.dummy_text_view)).check(matches(withText("This is dummy TextView for testing")))
+    }
+  }
+
+  @Module
+  class TestModule {
+    @Provides
+    @Singleton
+    fun provideContext(application: Application): Context {
+      return application
+    }
+
+    // TODO(#89): Introduce a proper IdlingResource for background dispatchers to ensure they all complete before
+    //  proceeding in an Espresso test. This solution should also be interoperative with Robolectric contexts by using a
+    //  test coroutine dispatcher.
+
+    @Singleton
+    @Provides
+    @BackgroundDispatcher
+    fun provideBackgroundDispatcher(@BlockingDispatcher blockingDispatcher: CoroutineDispatcher): CoroutineDispatcher {
+      return blockingDispatcher
+    }
+  }
+
+  @Singleton
+  @Component(modules = [TestModule::class])
+  interface TestApplicationComponent {
+    @Component.Builder
+    interface Builder {
+      @BindsInstance
+      fun setApplication(application: Application): Builder
+
+      fun build(): TestApplicationComponent
+    }
+  }
+}

From 6321130af56c22cb3e6d87784b918e58e4417156 Mon Sep 17 00:00:00 2001
From: Rajat Talesra <talesra@talesra-macbookpro.roam.corp.google.com>
Date: Sun, 6 Oct 2019 21:11:46 +0530
Subject: [PATCH 16/28] Nit changes

---
 .../java/org/oppia/app/topic/TopicActivityPresenter.kt     | 7 +++----
 1 file changed, 3 insertions(+), 4 deletions(-)

diff --git a/app/src/main/java/org/oppia/app/topic/TopicActivityPresenter.kt b/app/src/main/java/org/oppia/app/topic/TopicActivityPresenter.kt
index cec58a91b1d..2e807be8c74 100644
--- a/app/src/main/java/org/oppia/app/topic/TopicActivityPresenter.kt
+++ b/app/src/main/java/org/oppia/app/topic/TopicActivityPresenter.kt
@@ -3,7 +3,6 @@ package org.oppia.app.topic
 import androidx.appcompat.app.AppCompatActivity
 import org.oppia.app.R
 import org.oppia.app.activity.ActivityScope
-import org.oppia.app.topic.train.TopicTrainFragment
 import javax.inject.Inject
 
 /** The presenter for [TopicActivity]. */
@@ -14,12 +13,12 @@ class TopicActivityPresenter @Inject constructor(private val activity: AppCompat
     if (getTopicFragment() == null) {
       activity.supportFragmentManager.beginTransaction().add(
         R.id.topic_fragment_placeholder,
-        TopicTrainFragment()
+        TopicFragment()
       ).commitNow()
     }
   }
 
-  private fun getTopicFragment(): TopicTrainFragment? {
-    return activity.supportFragmentManager.findFragmentById(R.id.topic_fragment_placeholder) as TopicTrainFragment?
+  private fun getTopicFragment(): TopicFragment? {
+    return activity.supportFragmentManager.findFragmentById(R.id.topic_fragment_placeholder) as TopicFragment?
   }
 }

From 7bb449b1f8633c227267e6eef3b8c4f42185802c Mon Sep 17 00:00:00 2001
From: Rajat Talesra <talesra@talesra-macbookpro.roam.corp.google.com>
Date: Mon, 7 Oct 2019 09:41:18 +0530
Subject: [PATCH 17/28] More test cases

---
 .../java/org/oppia/app/RecyclerViewMatcher.kt |  54 +++++++++
 .../app/topic/train/TopicTrainFragmentTest.kt | 109 ++++++++++++++++--
 2 files changed, 155 insertions(+), 8 deletions(-)
 create mode 100644 app/src/sharedTest/java/org/oppia/app/RecyclerViewMatcher.kt

diff --git a/app/src/sharedTest/java/org/oppia/app/RecyclerViewMatcher.kt b/app/src/sharedTest/java/org/oppia/app/RecyclerViewMatcher.kt
new file mode 100644
index 00000000000..5674c95321c
--- /dev/null
+++ b/app/src/sharedTest/java/org/oppia/app/RecyclerViewMatcher.kt
@@ -0,0 +1,54 @@
+package org.oppia.app
+
+import android.content.res.Resources
+import android.view.View
+import androidx.recyclerview.widget.RecyclerView
+import org.hamcrest.Description
+import org.hamcrest.Matcher
+import org.hamcrest.TypeSafeMatcher
+
+class RecyclerViewMatcher(private val recyclerViewId: Int) {
+  fun atPosition(position: Int): Matcher<View> {
+    return atPositionOnView(position, -1)
+  }
+
+  fun atPositionOnView(position: Int, targetViewId: Int): Matcher<View> {
+    return object : TypeSafeMatcher<View>() {
+      var resources: Resources? = null
+      var childView: View? = null
+
+      override fun describeTo(description: Description) {
+        var idDescription = Integer.toString(recyclerViewId)
+        if (this.resources != null) {
+          idDescription = try {
+            this.resources!!.getResourceName(recyclerViewId)
+          } catch (var4: Resources.NotFoundException) {
+            String.format(
+              "%s (resource name not found)",
+              recyclerViewId
+            )
+          }
+        }
+        description.appendText("with id: $idDescription")
+      }
+
+      public override fun matchesSafely(view: View): Boolean {
+        this.resources = view.resources
+        if (childView == null) {
+          val recyclerView = view.rootView.findViewById<View>(recyclerViewId) as RecyclerView
+          if (recyclerView.id == recyclerViewId) {
+            childView = recyclerView.findViewHolderForAdapterPosition(position)!!.itemView
+          } else {
+            return false
+          }
+        }
+        return if (targetViewId == -1) {
+          view === childView
+        } else {
+          val targetView = childView!!.findViewById<View>(targetViewId)
+          view === targetView
+        }
+      }
+    }
+  }
+}
\ No newline at end of file
diff --git a/app/src/sharedTest/java/org/oppia/app/topic/train/TopicTrainFragmentTest.kt b/app/src/sharedTest/java/org/oppia/app/topic/train/TopicTrainFragmentTest.kt
index 051a6531429..463aa18580e 100644
--- a/app/src/sharedTest/java/org/oppia/app/topic/train/TopicTrainFragmentTest.kt
+++ b/app/src/sharedTest/java/org/oppia/app/topic/train/TopicTrainFragmentTest.kt
@@ -2,16 +2,19 @@ package org.oppia.app.topic.train
 
 import android.app.Application
 import android.content.Context
+import android.content.pm.ActivityInfo
 import androidx.test.core.app.ActivityScenario
 import androidx.test.espresso.Espresso.onView
 import androidx.test.espresso.action.ViewActions.click
-import androidx.test.espresso.action.ViewActions.scrollTo
 import androidx.test.espresso.assertion.ViewAssertions.matches
+import androidx.test.espresso.intent.Intents.intended
+import androidx.test.espresso.matcher.ViewMatchers.hasDescendant
 import androidx.test.espresso.matcher.ViewMatchers.isClickable
-import androidx.test.espresso.matcher.ViewMatchers.isNotChecked
 import androidx.test.espresso.matcher.ViewMatchers.withId
 import androidx.test.espresso.matcher.ViewMatchers.withText
 import androidx.test.ext.junit.runners.AndroidJUnit4
+import androidx.test.espresso.intent.matcher.IntentMatchers.hasExtra
+import androidx.test.espresso.intent.matcher.IntentMatchers.hasComponent
 import dagger.BindsInstance
 import dagger.Component
 import dagger.Module
@@ -20,27 +23,117 @@ import kotlinx.coroutines.CoroutineDispatcher
 import org.hamcrest.Matchers.not
 import org.junit.Test
 import org.junit.runner.RunWith
-import org.oppia.app.R
-import org.oppia.app.home.HomeActivity
+import org.oppia.app.topic.TopicActivity
 import org.oppia.util.threading.BackgroundDispatcher
 import org.oppia.util.threading.BlockingDispatcher
 import javax.inject.Singleton
+import androidx.test.espresso.intent.Intents
+import androidx.test.espresso.matcher.ViewMatchers.isChecked
+import org.oppia.app.R
+import org.oppia.app.RecyclerViewMatcher
+import org.junit.After
+import org.junit.Before
+import org.junit.Rule
+import androidx.test.rule.ActivityTestRule
 
 /** Tests for [TopicTrainFragment]. */
 @RunWith(AndroidJUnit4::class)
 class TopicTrainFragmentTest {
 
+  private var skillIdListIntent = ArrayList<String>()
+
+  @get:Rule
+  var activityTestRule: ActivityTestRule<TopicActivity> = ActivityTestRule(
+    TopicActivity::class.java, /* initialTouchMode= */ true, /* launchActivity= */ false
+  )
+
+  @Before
+  fun setUp() {
+    Intents.init()
+    skillIdListIntent.add("test_skill_id_0")
+    skillIdListIntent.add("test_skill_id_1")
+  }
+
   @Test
-  fun testTopicTrainFragment_loadFragment_selectSkills_submitButtonIsActivated() {
-    ActivityScenario.launch(HomeActivity::class.java).use {
+  fun testTopicTrainFragment_loadFragment_displaySkills_startButtonIsInactive() {
+    ActivityScenario.launch(TopicActivity::class.java).use {
       onView(withId(R.id.master_skills_text_view)).check(matches(withText(R.string.topic_train_master_these_skills)))
+      onView(withRecyclerView(R.id.skill_recycler_view).atPosition(0))
+        .check(matches(hasDescendant(withId(R.id.skill_check_box))))
       onView(withId(R.id.topic_train_start_button)).check(matches(not(isClickable())))
-      onView(withText("Writing Fractions")).check(matches(isNotChecked())).perform(scrollTo(), click())
-      onView(withText("Equivalent Fractions")).check(matches(isNotChecked())).perform(scrollTo(), click())
+    }
+  }
+
+  @Test
+  fun testTopicTrainFragment_loadFragment_selectSkills_deselectSkills_startButtonIsInactive() {
+    ActivityScenario.launch(TopicActivity::class.java).use {
+      onView(withId(R.id.master_skills_text_view)).check(matches(withText(R.string.topic_train_master_these_skills)))
+      onView(withRecyclerView(R.id.skill_recycler_view).atPosition(0)).perform(click())
       onView(withId(R.id.topic_train_start_button)).check(matches(isClickable()))
+      onView(withRecyclerView(R.id.skill_recycler_view).atPosition(0)).perform(click())
+      onView(withId(R.id.topic_train_start_button)).check(matches(not(isClickable())))
     }
   }
 
+  @Test
+  fun testTopicTrainFragment_loadFragment_selectSkills_clickStartButton_skillListTransferSuccessfully() {
+    activityTestRule.launchActivity(null)
+    onView(withId(R.id.master_skills_text_view)).check(matches(withText(R.string.topic_train_master_these_skills)))
+    onView(withRecyclerView(R.id.skill_recycler_view).atPosition(0)).perform(click())
+    onView(withRecyclerView(R.id.skill_recycler_view).atPosition(1)).perform(click())
+    onView(withId(R.id.topic_train_start_button)).check(matches(isClickable()))
+    onView(withId(R.id.topic_train_start_button)).perform(click())
+    intended(hasComponent("org.oppia.app.topic.questionplayer.QuestionPlayerActivity"))
+    intended(hasExtra("QuestionPlayerActivity.skill_id_list", skillIdListIntent))
+  }
+
+  @Test
+  fun testTopicTrainFragment_loadFragment_selectSkills_configurationChange_skillsAreSelected() {
+    activityTestRule.launchActivity(null)
+    onView(withId(R.id.master_skills_text_view)).check(matches(withText(R.string.topic_train_master_these_skills)))
+    onView(withRecyclerView(R.id.skill_recycler_view).atPosition(0)).perform(click())
+    activityTestRule.activity.requestedOrientation = ActivityInfo.SCREEN_ORIENTATION_LANDSCAPE
+    onView(
+      withRecyclerView(R.id.skill_recycler_view).atPositionOnView(
+        0,
+        R.id.skill_check_box
+      )
+    ).check(matches(isChecked()))
+  }
+
+  @Test
+  fun testTopicTrainFragment_loadFragment_configurationChange_startButtonRemainsInactive() {
+    activityTestRule.launchActivity(null)
+    onView(withId(R.id.topic_train_start_button)).check(matches(not(isClickable())))
+    activityTestRule.activity.requestedOrientation = ActivityInfo.SCREEN_ORIENTATION_LANDSCAPE
+    onView(withId(R.id.topic_train_start_button)).check(matches(not(isClickable())))
+  }
+
+  @Test
+  fun testTopicTrainFragment_loadFragment_selectSkills_configurationChange_startButtonRemainsActive() {
+    activityTestRule.launchActivity(null)
+    onView(withId(R.id.master_skills_text_view)).check(matches(withText(R.string.topic_train_master_these_skills)))
+    onView(withRecyclerView(R.id.skill_recycler_view).atPosition(0)).perform(click())
+    onView(withId(R.id.topic_train_start_button)).check(matches(isClickable()))
+    activityTestRule.activity.requestedOrientation = ActivityInfo.SCREEN_ORIENTATION_LANDSCAPE
+    onView(
+      withRecyclerView(R.id.skill_recycler_view).atPositionOnView(
+        0,
+        R.id.skill_check_box
+      )
+    ).check(matches(isChecked()))
+    onView(withId(R.id.topic_train_start_button)).check(matches(isClickable()))
+  }
+
+  private fun withRecyclerView(recyclerViewId: Int): RecyclerViewMatcher {
+    return RecyclerViewMatcher(recyclerViewId)
+  }
+
+  @After
+  fun tearDown() {
+    Intents.release()
+  }
+
   @Module
   class TestModule {
     @Provides

From 06f03b9679d2afc30ae846df452c7c27d8897f00 Mon Sep 17 00:00:00 2001
From: Rajat Talesra <talesra@talesra-macbookpro.roam.corp.google.com>
Date: Mon, 7 Oct 2019 09:44:34 +0530
Subject: [PATCH 18/28] Nit changes

---
 .../oppia/app/topic/questionplayer/QuestionPlayerActivity.kt   | 3 +--
 .../java/org/oppia/app/topic/train/SkillSelectionAdapter.kt    | 1 -
 .../main/java/org/oppia/app/topic/train/TopicTrainViewModel.kt | 2 --
 3 files changed, 1 insertion(+), 5 deletions(-)

diff --git a/app/src/main/java/org/oppia/app/topic/questionplayer/QuestionPlayerActivity.kt b/app/src/main/java/org/oppia/app/topic/questionplayer/QuestionPlayerActivity.kt
index d506601c5ce..b8a404f524a 100644
--- a/app/src/main/java/org/oppia/app/topic/questionplayer/QuestionPlayerActivity.kt
+++ b/app/src/main/java/org/oppia/app/topic/questionplayer/QuestionPlayerActivity.kt
@@ -4,7 +4,6 @@ import android.content.Context
 import android.content.Intent
 import android.os.Bundle
 import org.oppia.app.activity.InjectableAppCompatActivity
-import org.oppia.app.topic.TopicActivity
 import javax.inject.Inject
 
 const val QUESTION_PLAYER_ACTIVITY_SKILL_ID_LIST_ARGUMENT_KEY = "QuestionPlayerActivity.skill_id_list"
@@ -22,7 +21,7 @@ class QuestionPlayerActivity : InjectableAppCompatActivity() {
 
   companion object {
     // TODO(#159): Use this skillList from TopicTrainFragment to fetch questions and start train mode.
-    /** Returns a new [Intent] to route to [TopicActivity] for a specified skill ID list. */
+    /** Returns a new [Intent] to route to [QuestionPlayerActivity] for a specified skill ID list. */
     fun createQuestionPlayerActivityIntent(context: Context, skillIdList: ArrayList<String>): Intent {
       val intent = Intent(context, QuestionPlayerActivity::class.java)
       intent.putExtra(QUESTION_PLAYER_ACTIVITY_SKILL_ID_LIST_ARGUMENT_KEY, skillIdList)
diff --git a/app/src/main/java/org/oppia/app/topic/train/SkillSelectionAdapter.kt b/app/src/main/java/org/oppia/app/topic/train/SkillSelectionAdapter.kt
index 36e09f14b11..f3e9527e8f1 100644
--- a/app/src/main/java/org/oppia/app/topic/train/SkillSelectionAdapter.kt
+++ b/app/src/main/java/org/oppia/app/topic/train/SkillSelectionAdapter.kt
@@ -1,6 +1,5 @@
 package org.oppia.app.topic.train
 
-import android.util.Log
 import android.view.LayoutInflater
 import android.view.ViewGroup
 import androidx.databinding.DataBindingUtil
diff --git a/app/src/main/java/org/oppia/app/topic/train/TopicTrainViewModel.kt b/app/src/main/java/org/oppia/app/topic/train/TopicTrainViewModel.kt
index 216fe9be652..453758f3f0b 100644
--- a/app/src/main/java/org/oppia/app/topic/train/TopicTrainViewModel.kt
+++ b/app/src/main/java/org/oppia/app/topic/train/TopicTrainViewModel.kt
@@ -1,6 +1,5 @@
 package org.oppia.app.topic.train
 
-import android.util.Log
 import android.view.View
 import androidx.databinding.ObservableField
 import androidx.lifecycle.ViewModel
@@ -16,7 +15,6 @@ class TopicTrainViewModel @Inject constructor(
   var isSubmitButtonActive = ObservableField<Boolean>(false)
 
   fun selectedSkillList(selectedSkillList: ArrayList<String>) {
-    Log.d("TAG", "Size: "+selectedSkillList.size)
     isSubmitButtonActive.set(selectedSkillList.isNotEmpty())
   }
 

From 81eee40c25af502928bb32758d5b8682b6ac2552 Mon Sep 17 00:00:00 2001
From: Rajat Talesra <talesra@talesra-macbookpro.roam.corp.google.com>
Date: Mon, 7 Oct 2019 16:28:18 +0530
Subject: [PATCH 19/28] EOF added

---
 app/src/sharedTest/java/org/oppia/app/RecyclerViewMatcher.kt | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/app/src/sharedTest/java/org/oppia/app/RecyclerViewMatcher.kt b/app/src/sharedTest/java/org/oppia/app/RecyclerViewMatcher.kt
index 5674c95321c..02fffb27d42 100644
--- a/app/src/sharedTest/java/org/oppia/app/RecyclerViewMatcher.kt
+++ b/app/src/sharedTest/java/org/oppia/app/RecyclerViewMatcher.kt
@@ -51,4 +51,4 @@ class RecyclerViewMatcher(private val recyclerViewId: Int) {
       }
     }
   }
-}
\ No newline at end of file
+}

From 45b1b18566448f11140dc138c38d521ae5bb2250 Mon Sep 17 00:00:00 2001
From: Rajat Talesra <talesra@talesra-macbookpro.roam.corp.google.com>
Date: Tue, 8 Oct 2019 22:43:27 +0530
Subject: [PATCH 20/28] Test nit changes

---
 .../app/topic/train/TopicTrainFragmentTest.kt      | 14 ++++----------
 1 file changed, 4 insertions(+), 10 deletions(-)

diff --git a/app/src/sharedTest/java/org/oppia/app/topic/train/TopicTrainFragmentTest.kt b/app/src/sharedTest/java/org/oppia/app/topic/train/TopicTrainFragmentTest.kt
index 463aa18580e..f3e31881a5d 100644
--- a/app/src/sharedTest/java/org/oppia/app/topic/train/TopicTrainFragmentTest.kt
+++ b/app/src/sharedTest/java/org/oppia/app/topic/train/TopicTrainFragmentTest.kt
@@ -40,7 +40,7 @@ import androidx.test.rule.ActivityTestRule
 @RunWith(AndroidJUnit4::class)
 class TopicTrainFragmentTest {
 
-  private var skillIdListIntent = ArrayList<String>()
+  private var skillIdList = ArrayList<String>()
 
   @get:Rule
   var activityTestRule: ActivityTestRule<TopicActivity> = ActivityTestRule(
@@ -50,8 +50,8 @@ class TopicTrainFragmentTest {
   @Before
   fun setUp() {
     Intents.init()
-    skillIdListIntent.add("test_skill_id_0")
-    skillIdListIntent.add("test_skill_id_1")
+    skillIdList.add("test_skill_id_0")
+    skillIdList.add("test_skill_id_1")
   }
 
   @Test
@@ -84,7 +84,7 @@ class TopicTrainFragmentTest {
     onView(withId(R.id.topic_train_start_button)).check(matches(isClickable()))
     onView(withId(R.id.topic_train_start_button)).perform(click())
     intended(hasComponent("org.oppia.app.topic.questionplayer.QuestionPlayerActivity"))
-    intended(hasExtra("QuestionPlayerActivity.skill_id_list", skillIdListIntent))
+    intended(hasExtra("QuestionPlayerActivity.skill_id_list", skillIdList))
   }
 
   @Test
@@ -116,12 +116,6 @@ class TopicTrainFragmentTest {
     onView(withRecyclerView(R.id.skill_recycler_view).atPosition(0)).perform(click())
     onView(withId(R.id.topic_train_start_button)).check(matches(isClickable()))
     activityTestRule.activity.requestedOrientation = ActivityInfo.SCREEN_ORIENTATION_LANDSCAPE
-    onView(
-      withRecyclerView(R.id.skill_recycler_view).atPositionOnView(
-        0,
-        R.id.skill_check_box
-      )
-    ).check(matches(isChecked()))
     onView(withId(R.id.topic_train_start_button)).check(matches(isClickable()))
   }
 

From d9f586deb06ef71274735364aa34d77b45d46e93 Mon Sep 17 00:00:00 2001
From: Rajat Talesra <talesra@talesra-macbookpro.roam.corp.google.com>
Date: Wed, 9 Oct 2019 11:32:30 +0530
Subject: [PATCH 21/28] Test case updated

---
 .../oppia/app/topic/questionplayer/QuestionPlayerActivity.kt | 4 ++++
 .../java/org/oppia/app/topic/train/TopicTrainFragmentTest.kt | 5 +++--
 2 files changed, 7 insertions(+), 2 deletions(-)

diff --git a/app/src/main/java/org/oppia/app/topic/questionplayer/QuestionPlayerActivity.kt b/app/src/main/java/org/oppia/app/topic/questionplayer/QuestionPlayerActivity.kt
index b8a404f524a..38ffaa98ed5 100644
--- a/app/src/main/java/org/oppia/app/topic/questionplayer/QuestionPlayerActivity.kt
+++ b/app/src/main/java/org/oppia/app/topic/questionplayer/QuestionPlayerActivity.kt
@@ -27,5 +27,9 @@ class QuestionPlayerActivity : InjectableAppCompatActivity() {
       intent.putExtra(QUESTION_PLAYER_ACTIVITY_SKILL_ID_LIST_ARGUMENT_KEY, skillIdList)
       return intent
     }
+
+    fun getIntentKey():String{
+      return QUESTION_PLAYER_ACTIVITY_SKILL_ID_LIST_ARGUMENT_KEY
+    }
   }
 }
diff --git a/app/src/sharedTest/java/org/oppia/app/topic/train/TopicTrainFragmentTest.kt b/app/src/sharedTest/java/org/oppia/app/topic/train/TopicTrainFragmentTest.kt
index f3e31881a5d..2ad05c9379f 100644
--- a/app/src/sharedTest/java/org/oppia/app/topic/train/TopicTrainFragmentTest.kt
+++ b/app/src/sharedTest/java/org/oppia/app/topic/train/TopicTrainFragmentTest.kt
@@ -35,6 +35,7 @@ import org.junit.After
 import org.junit.Before
 import org.junit.Rule
 import androidx.test.rule.ActivityTestRule
+import org.oppia.app.topic.questionplayer.QuestionPlayerActivity
 
 /** Tests for [TopicTrainFragment]. */
 @RunWith(AndroidJUnit4::class)
@@ -83,8 +84,8 @@ class TopicTrainFragmentTest {
     onView(withRecyclerView(R.id.skill_recycler_view).atPosition(1)).perform(click())
     onView(withId(R.id.topic_train_start_button)).check(matches(isClickable()))
     onView(withId(R.id.topic_train_start_button)).perform(click())
-    intended(hasComponent("org.oppia.app.topic.questionplayer.QuestionPlayerActivity"))
-    intended(hasExtra("QuestionPlayerActivity.skill_id_list", skillIdList))
+    intended(hasComponent(QuestionPlayerActivity::class.java.name))
+    intended(hasExtra(QuestionPlayerActivity.getIntentKey(), skillIdList))
   }
 
   @Test

From b7fb1e4c17c63d0eab61cefb6de779174f4d4394 Mon Sep 17 00:00:00 2001
From: Rajat Talesra <talesra@talesra-macbookpro.roam.corp.google.com>
Date: Fri, 11 Oct 2019 00:09:09 +0530
Subject: [PATCH 22/28] Updated RecyclerViewMatcher

---
 .../java/org/oppia/app/RecyclerViewMatcher.kt | 80 +++++++++++--------
 .../app/topic/train/TopicTrainFragmentTest.kt | 58 ++++++++------
 2 files changed, 79 insertions(+), 59 deletions(-)

diff --git a/app/src/sharedTest/java/org/oppia/app/RecyclerViewMatcher.kt b/app/src/sharedTest/java/org/oppia/app/RecyclerViewMatcher.kt
index 02fffb27d42..7eeda86211f 100644
--- a/app/src/sharedTest/java/org/oppia/app/RecyclerViewMatcher.kt
+++ b/app/src/sharedTest/java/org/oppia/app/RecyclerViewMatcher.kt
@@ -7,48 +7,60 @@ import org.hamcrest.Description
 import org.hamcrest.Matcher
 import org.hamcrest.TypeSafeMatcher
 
-class RecyclerViewMatcher(private val recyclerViewId: Int) {
-  fun atPosition(position: Int): Matcher<View> {
-    return atPositionOnView(position, -1)
-  }
+// Reference Link: https://github.com/dannyroa/espresso-samples/blob/master/RecyclerView/app/src/androidTest/java/com/dannyroa/espresso_samples/recyclerview/RecyclerViewMatcher.java
+class RecyclerViewMatcher {
+
+  companion object {
+
+    /**
+     * This function returns a Matcher for a item inside RecyclerView from a specified position.
+     */
+    fun atPosition(recyclerViewId: Int, position: Int): Matcher<View> {
+      return atPositionOnView(recyclerViewId, position, -1)
+    }
+
+    /**
+     * This function returns a Matcher for a specific view within the item inside RecyclerView from a specified position.
+     */
+    fun atPositionOnView(recyclerViewId: Int, position: Int, targetViewId: Int): Matcher<View> {
+      return object : TypeSafeMatcher<View>() {
+        var resources: Resources? = null
+        var childView: View? = null
 
-  fun atPositionOnView(position: Int, targetViewId: Int): Matcher<View> {
-    return object : TypeSafeMatcher<View>() {
-      var resources: Resources? = null
-      var childView: View? = null
-
-      override fun describeTo(description: Description) {
-        var idDescription = Integer.toString(recyclerViewId)
-        if (this.resources != null) {
-          idDescription = try {
-            this.resources!!.getResourceName(recyclerViewId)
-          } catch (var4: Resources.NotFoundException) {
-            String.format(
-              "%s (resource name not found)",
-              recyclerViewId
-            )
+        override fun describeTo(description: Description) {
+          var idDescription = Integer.toString(recyclerViewId)
+          if (this.resources != null) {
+            idDescription = try {
+              this.resources!!.getResourceName(recyclerViewId)
+            } catch (var4: Resources.NotFoundException) {
+              String.format(
+                "%s (resource name not found)",
+                recyclerViewId
+              )
+            }
           }
+          description.appendText("with id: $idDescription")
         }
-        description.appendText("with id: $idDescription")
-      }
 
-      public override fun matchesSafely(view: View): Boolean {
-        this.resources = view.resources
-        if (childView == null) {
-          val recyclerView = view.rootView.findViewById<View>(recyclerViewId) as RecyclerView
-          if (recyclerView.id == recyclerViewId) {
-            childView = recyclerView.findViewHolderForAdapterPosition(position)!!.itemView
+        public override fun matchesSafely(view: View): Boolean {
+          this.resources = view.resources
+          if (childView == null) {
+            val recyclerView = view.rootView.findViewById<View>(recyclerViewId) as RecyclerView
+            if (recyclerView.id == recyclerViewId) {
+              childView = recyclerView.findViewHolderForAdapterPosition(position)!!.itemView
+            } else {
+              return false
+            }
+          }
+          return if (targetViewId == -1) {
+            view === childView
           } else {
-            return false
+            val targetView = childView!!.findViewById<View>(targetViewId)
+            view === targetView
           }
         }
-        return if (targetViewId == -1) {
-          view === childView
-        } else {
-          val targetView = childView!!.findViewById<View>(targetViewId)
-          view === targetView
-        }
       }
     }
+
   }
 }
diff --git a/app/src/sharedTest/java/org/oppia/app/topic/train/TopicTrainFragmentTest.kt b/app/src/sharedTest/java/org/oppia/app/topic/train/TopicTrainFragmentTest.kt
index 2ad05c9379f..9f0d1c13fee 100644
--- a/app/src/sharedTest/java/org/oppia/app/topic/train/TopicTrainFragmentTest.kt
+++ b/app/src/sharedTest/java/org/oppia/app/topic/train/TopicTrainFragmentTest.kt
@@ -30,11 +30,12 @@ import javax.inject.Singleton
 import androidx.test.espresso.intent.Intents
 import androidx.test.espresso.matcher.ViewMatchers.isChecked
 import org.oppia.app.R
-import org.oppia.app.RecyclerViewMatcher
 import org.junit.After
 import org.junit.Before
 import org.junit.Rule
 import androidx.test.rule.ActivityTestRule
+import org.oppia.app.RecyclerViewMatcher.Companion.atPosition
+import org.oppia.app.RecyclerViewMatcher.Companion.atPositionOnView
 import org.oppia.app.topic.questionplayer.QuestionPlayerActivity
 
 /** Tests for [TopicTrainFragment]. */
@@ -59,19 +60,41 @@ class TopicTrainFragmentTest {
   fun testTopicTrainFragment_loadFragment_displaySkills_startButtonIsInactive() {
     ActivityScenario.launch(TopicActivity::class.java).use {
       onView(withId(R.id.master_skills_text_view)).check(matches(withText(R.string.topic_train_master_these_skills)))
-      onView(withRecyclerView(R.id.skill_recycler_view).atPosition(0))
+      onView(atPosition(R.id.skill_recycler_view,0))
         .check(matches(hasDescendant(withId(R.id.skill_check_box))))
       onView(withId(R.id.topic_train_start_button)).check(matches(not(isClickable())))
     }
   }
 
   @Test
-  fun testTopicTrainFragment_loadFragment_selectSkills_deselectSkills_startButtonIsInactive() {
+  fun testTopicTrainFragment_loadFragment_selectSkills_isSuccessful() {
     ActivityScenario.launch(TopicActivity::class.java).use {
-      onView(withId(R.id.master_skills_text_view)).check(matches(withText(R.string.topic_train_master_these_skills)))
-      onView(withRecyclerView(R.id.skill_recycler_view).atPosition(0)).perform(click())
+      onView(atPosition(R.id.skill_recycler_view,0)).perform(click())
+      onView(atPosition(R.id.skill_recycler_view,1)).perform(click())
+    }
+  }
+
+  @Test
+  fun testTopicTrainFragment_loadFragment_selectSkills_startButtonIsActive() {
+    ActivityScenario.launch(TopicActivity::class.java).use {
+      onView(atPosition(R.id.skill_recycler_view,0)).perform(click())
       onView(withId(R.id.topic_train_start_button)).check(matches(isClickable()))
-      onView(withRecyclerView(R.id.skill_recycler_view).atPosition(0)).perform(click())
+    }
+  }
+
+  @Test
+  fun testTopicTrainFragment_loadFragment_selectSkills_deselectSkills_isSuccessful() {
+    ActivityScenario.launch(TopicActivity::class.java).use {
+      onView(atPosition(R.id.skill_recycler_view,0)).perform(click())
+      onView(atPosition(R.id.skill_recycler_view,0)).perform(click())
+    }
+  }
+
+  @Test
+  fun testTopicTrainFragment_loadFragment_selectSkills_deselectSkills_startButtonIsInactive() {
+    ActivityScenario.launch(TopicActivity::class.java).use {
+      onView(atPosition(R.id.skill_recycler_view,0)).perform(click())
+      onView(atPosition(R.id.skill_recycler_view,0)).perform(click())
       onView(withId(R.id.topic_train_start_button)).check(matches(not(isClickable())))
     }
   }
@@ -79,10 +102,7 @@ class TopicTrainFragmentTest {
   @Test
   fun testTopicTrainFragment_loadFragment_selectSkills_clickStartButton_skillListTransferSuccessfully() {
     activityTestRule.launchActivity(null)
-    onView(withId(R.id.master_skills_text_view)).check(matches(withText(R.string.topic_train_master_these_skills)))
-    onView(withRecyclerView(R.id.skill_recycler_view).atPosition(0)).perform(click())
-    onView(withRecyclerView(R.id.skill_recycler_view).atPosition(1)).perform(click())
-    onView(withId(R.id.topic_train_start_button)).check(matches(isClickable()))
+    onView(atPosition(R.id.skill_recycler_view,0)).perform(click())
     onView(withId(R.id.topic_train_start_button)).perform(click())
     intended(hasComponent(QuestionPlayerActivity::class.java.name))
     intended(hasExtra(QuestionPlayerActivity.getIntentKey(), skillIdList))
@@ -91,15 +111,9 @@ class TopicTrainFragmentTest {
   @Test
   fun testTopicTrainFragment_loadFragment_selectSkills_configurationChange_skillsAreSelected() {
     activityTestRule.launchActivity(null)
-    onView(withId(R.id.master_skills_text_view)).check(matches(withText(R.string.topic_train_master_these_skills)))
-    onView(withRecyclerView(R.id.skill_recycler_view).atPosition(0)).perform(click())
+    onView(atPosition(R.id.skill_recycler_view,0)).perform(click())
     activityTestRule.activity.requestedOrientation = ActivityInfo.SCREEN_ORIENTATION_LANDSCAPE
-    onView(
-      withRecyclerView(R.id.skill_recycler_view).atPositionOnView(
-        0,
-        R.id.skill_check_box
-      )
-    ).check(matches(isChecked()))
+    onView(atPositionOnView(R.id.skill_recycler_view, 0, R.id.skill_check_box)).check(matches(isChecked()))
   }
 
   @Test
@@ -113,17 +127,11 @@ class TopicTrainFragmentTest {
   @Test
   fun testTopicTrainFragment_loadFragment_selectSkills_configurationChange_startButtonRemainsActive() {
     activityTestRule.launchActivity(null)
-    onView(withId(R.id.master_skills_text_view)).check(matches(withText(R.string.topic_train_master_these_skills)))
-    onView(withRecyclerView(R.id.skill_recycler_view).atPosition(0)).perform(click())
-    onView(withId(R.id.topic_train_start_button)).check(matches(isClickable()))
+    onView(atPosition(R.id.skill_recycler_view,0)).perform(click())
     activityTestRule.activity.requestedOrientation = ActivityInfo.SCREEN_ORIENTATION_LANDSCAPE
     onView(withId(R.id.topic_train_start_button)).check(matches(isClickable()))
   }
 
-  private fun withRecyclerView(recyclerViewId: Int): RecyclerViewMatcher {
-    return RecyclerViewMatcher(recyclerViewId)
-  }
-
   @After
   fun tearDown() {
     Intents.release()

From 9e81bb5bb6604b37dba6514cd278516b61a7ff94 Mon Sep 17 00:00:00 2001
From: Rajat Talesra <talesra@talesra-macbookpro.roam.corp.google.com>
Date: Fri, 11 Oct 2019 00:11:27 +0530
Subject: [PATCH 23/28] Nit change

---
 .../org/oppia/app/{ => recyclerview}/RecyclerViewMatcher.kt  | 4 ++--
 .../java/org/oppia/app/topic/train/TopicTrainFragmentTest.kt | 5 ++---
 2 files changed, 4 insertions(+), 5 deletions(-)
 rename app/src/sharedTest/java/org/oppia/app/{ => recyclerview}/RecyclerViewMatcher.kt (94%)

diff --git a/app/src/sharedTest/java/org/oppia/app/RecyclerViewMatcher.kt b/app/src/sharedTest/java/org/oppia/app/recyclerview/RecyclerViewMatcher.kt
similarity index 94%
rename from app/src/sharedTest/java/org/oppia/app/RecyclerViewMatcher.kt
rename to app/src/sharedTest/java/org/oppia/app/recyclerview/RecyclerViewMatcher.kt
index 7eeda86211f..2c51333a942 100644
--- a/app/src/sharedTest/java/org/oppia/app/RecyclerViewMatcher.kt
+++ b/app/src/sharedTest/java/org/oppia/app/recyclerview/RecyclerViewMatcher.kt
@@ -1,4 +1,4 @@
-package org.oppia.app
+package org.oppia.app.recyclerview
 
 import android.content.res.Resources
 import android.view.View
@@ -13,7 +13,7 @@ class RecyclerViewMatcher {
   companion object {
 
     /**
-     * This function returns a Matcher for a item inside RecyclerView from a specified position.
+     * This function returns a Matcher for an item inside RecyclerView from a specified position.
      */
     fun atPosition(recyclerViewId: Int, position: Int): Matcher<View> {
       return atPositionOnView(recyclerViewId, position, -1)
diff --git a/app/src/sharedTest/java/org/oppia/app/topic/train/TopicTrainFragmentTest.kt b/app/src/sharedTest/java/org/oppia/app/topic/train/TopicTrainFragmentTest.kt
index 9f0d1c13fee..9f0a87a7425 100644
--- a/app/src/sharedTest/java/org/oppia/app/topic/train/TopicTrainFragmentTest.kt
+++ b/app/src/sharedTest/java/org/oppia/app/topic/train/TopicTrainFragmentTest.kt
@@ -34,8 +34,8 @@ import org.junit.After
 import org.junit.Before
 import org.junit.Rule
 import androidx.test.rule.ActivityTestRule
-import org.oppia.app.RecyclerViewMatcher.Companion.atPosition
-import org.oppia.app.RecyclerViewMatcher.Companion.atPositionOnView
+import org.oppia.app.recyclerview.RecyclerViewMatcher.Companion.atPosition
+import org.oppia.app.recyclerview.RecyclerViewMatcher.Companion.atPositionOnView
 import org.oppia.app.topic.questionplayer.QuestionPlayerActivity
 
 /** Tests for [TopicTrainFragment]. */
@@ -53,7 +53,6 @@ class TopicTrainFragmentTest {
   fun setUp() {
     Intents.init()
     skillIdList.add("test_skill_id_0")
-    skillIdList.add("test_skill_id_1")
   }
 
   @Test

From 52740778c4779fb6eb4c162378d63cc5a7177e54 Mon Sep 17 00:00:00 2001
From: Rajat Talesra <talesra@talesra-macbookpro.roam.corp.google.com>
Date: Fri, 11 Oct 2019 11:51:32 +0530
Subject: [PATCH 24/28] Test added

---
 .../app/recyclerview/BindableAdapterTest.kt   | 60 ++++++++++++++++-
 .../app/recyclerview/RecyclerViewMatcher.kt   | 66 -------------------
 .../app/topic/train/TopicTrainFragmentTest.kt | 29 ++++----
 3 files changed, 71 insertions(+), 84 deletions(-)
 delete mode 100644 app/src/sharedTest/java/org/oppia/app/recyclerview/RecyclerViewMatcher.kt

diff --git a/app/src/sharedTest/java/org/oppia/app/recyclerview/BindableAdapterTest.kt b/app/src/sharedTest/java/org/oppia/app/recyclerview/BindableAdapterTest.kt
index 39423e79895..d9c8db7b657 100644
--- a/app/src/sharedTest/java/org/oppia/app/recyclerview/BindableAdapterTest.kt
+++ b/app/src/sharedTest/java/org/oppia/app/recyclerview/BindableAdapterTest.kt
@@ -1,5 +1,6 @@
 package org.oppia.app.recyclerview
 
+import android.content.res.Resources
 import android.view.LayoutInflater
 import android.view.ViewGroup
 import android.widget.TextView
@@ -30,6 +31,7 @@ import androidx.test.espresso.matcher.BoundedMatcher
 import android.view.View
 import org.hamcrest.Description
 import org.hamcrest.Matcher
+import org.hamcrest.TypeSafeMatcher
 import org.oppia.app.databinding.TestTextViewForIntWithDataBindingBinding
 import org.oppia.app.databinding.TestTextViewForStringWithDataBindingBinding
 
@@ -273,13 +275,15 @@ class BindableAdapterTest {
   private fun inflateTextViewForStringWithoutDataBinding(viewGroup: ViewGroup): TextView {
     val inflater = LayoutInflater.from(ApplicationProvider.getApplicationContext())
     return inflater.inflate(
-      R.layout.test_text_view_for_string_no_data_binding, viewGroup, /* attachToRoot= */ false) as TextView
+      R.layout.test_text_view_for_string_no_data_binding, viewGroup, /* attachToRoot= */ false
+    ) as TextView
   }
 
   private fun inflateTextViewForIntWithoutDataBinding(viewGroup: ViewGroup): TextView {
     val inflater = LayoutInflater.from(ApplicationProvider.getApplicationContext())
     return inflater.inflate(
-      R.layout.test_text_view_for_int_no_data_binding, viewGroup, /* attachToRoot= */ false) as TextView
+      R.layout.test_text_view_for_int_no_data_binding, viewGroup, /* attachToRoot= */ false
+    ) as TextView
   }
 
   private fun bindTextViewForStringWithoutDataBinding(textView: TextView, data: TestModel) {
@@ -313,7 +317,7 @@ class BindableAdapterTest {
 
   // TODO(#89): Move this to a consolidated test library.
   // https://stackoverflow.com/a/34795431
-  private fun atPosition(position: Int, itemMatcher: Matcher<View>): Matcher<View> {
+  fun atPosition(position: Int, itemMatcher: Matcher<View>): Matcher<View> {
     return object : BoundedMatcher<View, RecyclerView>(RecyclerView::class.java) {
       override fun describeTo(description: Description) {
         description.appendText("has item at position $position: ")
@@ -326,4 +330,54 @@ class BindableAdapterTest {
       }
     }
   }
+
+  /**
+   * This function returns a Matcher for an item inside RecyclerView from a specified position.
+   */
+  fun atPosition(recyclerViewId: Int, position: Int): Matcher<View> {
+    return atPositionOnView(recyclerViewId, position, -1)
+  }
+
+  /**
+   * This function returns a Matcher for a specific view within the item inside RecyclerView from a specified position.
+   */
+  fun atPositionOnView(recyclerViewId: Int, position: Int, targetViewId: Int): Matcher<View> {
+    return object : TypeSafeMatcher<View>() {
+      var resources: Resources? = null
+      var childView: View? = null
+
+      override fun describeTo(description: Description) {
+        var idDescription = Integer.toString(recyclerViewId)
+        if (this.resources != null) {
+          idDescription = try {
+            this.resources!!.getResourceName(recyclerViewId)
+          } catch (var4: Resources.NotFoundException) {
+            String.format(
+              "%s (resource name not found)",
+              recyclerViewId
+            )
+          }
+        }
+        description.appendText("with id: $idDescription")
+      }
+
+      public override fun matchesSafely(view: View): Boolean {
+        this.resources = view.resources
+        if (childView == null) {
+          val recyclerView = view.rootView.findViewById<View>(recyclerViewId) as RecyclerView
+          if (recyclerView.id == recyclerViewId) {
+            childView = recyclerView.findViewHolderForAdapterPosition(position)!!.itemView
+          } else {
+            return false
+          }
+        }
+        return if (targetViewId == -1) {
+          view === childView
+        } else {
+          val targetView = childView!!.findViewById<View>(targetViewId)
+          view === targetView
+        }
+      }
+    }
+  }
 }
diff --git a/app/src/sharedTest/java/org/oppia/app/recyclerview/RecyclerViewMatcher.kt b/app/src/sharedTest/java/org/oppia/app/recyclerview/RecyclerViewMatcher.kt
deleted file mode 100644
index 2c51333a942..00000000000
--- a/app/src/sharedTest/java/org/oppia/app/recyclerview/RecyclerViewMatcher.kt
+++ /dev/null
@@ -1,66 +0,0 @@
-package org.oppia.app.recyclerview
-
-import android.content.res.Resources
-import android.view.View
-import androidx.recyclerview.widget.RecyclerView
-import org.hamcrest.Description
-import org.hamcrest.Matcher
-import org.hamcrest.TypeSafeMatcher
-
-// Reference Link: https://github.com/dannyroa/espresso-samples/blob/master/RecyclerView/app/src/androidTest/java/com/dannyroa/espresso_samples/recyclerview/RecyclerViewMatcher.java
-class RecyclerViewMatcher {
-
-  companion object {
-
-    /**
-     * This function returns a Matcher for an item inside RecyclerView from a specified position.
-     */
-    fun atPosition(recyclerViewId: Int, position: Int): Matcher<View> {
-      return atPositionOnView(recyclerViewId, position, -1)
-    }
-
-    /**
-     * This function returns a Matcher for a specific view within the item inside RecyclerView from a specified position.
-     */
-    fun atPositionOnView(recyclerViewId: Int, position: Int, targetViewId: Int): Matcher<View> {
-      return object : TypeSafeMatcher<View>() {
-        var resources: Resources? = null
-        var childView: View? = null
-
-        override fun describeTo(description: Description) {
-          var idDescription = Integer.toString(recyclerViewId)
-          if (this.resources != null) {
-            idDescription = try {
-              this.resources!!.getResourceName(recyclerViewId)
-            } catch (var4: Resources.NotFoundException) {
-              String.format(
-                "%s (resource name not found)",
-                recyclerViewId
-              )
-            }
-          }
-          description.appendText("with id: $idDescription")
-        }
-
-        public override fun matchesSafely(view: View): Boolean {
-          this.resources = view.resources
-          if (childView == null) {
-            val recyclerView = view.rootView.findViewById<View>(recyclerViewId) as RecyclerView
-            if (recyclerView.id == recyclerViewId) {
-              childView = recyclerView.findViewHolderForAdapterPosition(position)!!.itemView
-            } else {
-              return false
-            }
-          }
-          return if (targetViewId == -1) {
-            view === childView
-          } else {
-            val targetView = childView!!.findViewById<View>(targetViewId)
-            view === targetView
-          }
-        }
-      }
-    }
-
-  }
-}
diff --git a/app/src/sharedTest/java/org/oppia/app/topic/train/TopicTrainFragmentTest.kt b/app/src/sharedTest/java/org/oppia/app/topic/train/TopicTrainFragmentTest.kt
index 9f0a87a7425..0916dda813d 100644
--- a/app/src/sharedTest/java/org/oppia/app/topic/train/TopicTrainFragmentTest.kt
+++ b/app/src/sharedTest/java/org/oppia/app/topic/train/TopicTrainFragmentTest.kt
@@ -34,8 +34,7 @@ import org.junit.After
 import org.junit.Before
 import org.junit.Rule
 import androidx.test.rule.ActivityTestRule
-import org.oppia.app.recyclerview.RecyclerViewMatcher.Companion.atPosition
-import org.oppia.app.recyclerview.RecyclerViewMatcher.Companion.atPositionOnView
+import org.oppia.app.recyclerview.BindableAdapterTest
 import org.oppia.app.topic.questionplayer.QuestionPlayerActivity
 
 /** Tests for [TopicTrainFragment]. */
@@ -43,6 +42,7 @@ import org.oppia.app.topic.questionplayer.QuestionPlayerActivity
 class TopicTrainFragmentTest {
 
   private var skillIdList = ArrayList<String>()
+  private val bindableAdapterTest:BindableAdapterTest = BindableAdapterTest()
 
   @get:Rule
   var activityTestRule: ActivityTestRule<TopicActivity> = ActivityTestRule(
@@ -59,8 +59,7 @@ class TopicTrainFragmentTest {
   fun testTopicTrainFragment_loadFragment_displaySkills_startButtonIsInactive() {
     ActivityScenario.launch(TopicActivity::class.java).use {
       onView(withId(R.id.master_skills_text_view)).check(matches(withText(R.string.topic_train_master_these_skills)))
-      onView(atPosition(R.id.skill_recycler_view,0))
-        .check(matches(hasDescendant(withId(R.id.skill_check_box))))
+      onView(bindableAdapterTest.atPosition(R.id.skill_recycler_view,0)).check(matches(hasDescendant(withId(R.id.skill_check_box))))
       onView(withId(R.id.topic_train_start_button)).check(matches(not(isClickable())))
     }
   }
@@ -68,15 +67,15 @@ class TopicTrainFragmentTest {
   @Test
   fun testTopicTrainFragment_loadFragment_selectSkills_isSuccessful() {
     ActivityScenario.launch(TopicActivity::class.java).use {
-      onView(atPosition(R.id.skill_recycler_view,0)).perform(click())
-      onView(atPosition(R.id.skill_recycler_view,1)).perform(click())
+      onView(bindableAdapterTest.atPosition(R.id.skill_recycler_view,0)).perform(click())
+      onView(bindableAdapterTest.atPosition(R.id.skill_recycler_view,1)).perform(click())
     }
   }
 
   @Test
   fun testTopicTrainFragment_loadFragment_selectSkills_startButtonIsActive() {
     ActivityScenario.launch(TopicActivity::class.java).use {
-      onView(atPosition(R.id.skill_recycler_view,0)).perform(click())
+      onView(bindableAdapterTest.atPosition(R.id.skill_recycler_view,0)).perform(click())
       onView(withId(R.id.topic_train_start_button)).check(matches(isClickable()))
     }
   }
@@ -84,16 +83,16 @@ class TopicTrainFragmentTest {
   @Test
   fun testTopicTrainFragment_loadFragment_selectSkills_deselectSkills_isSuccessful() {
     ActivityScenario.launch(TopicActivity::class.java).use {
-      onView(atPosition(R.id.skill_recycler_view,0)).perform(click())
-      onView(atPosition(R.id.skill_recycler_view,0)).perform(click())
+      onView(bindableAdapterTest.atPosition(R.id.skill_recycler_view,0)).perform(click())
+      onView(bindableAdapterTest.atPosition(R.id.skill_recycler_view,0)).perform(click())
     }
   }
 
   @Test
   fun testTopicTrainFragment_loadFragment_selectSkills_deselectSkills_startButtonIsInactive() {
     ActivityScenario.launch(TopicActivity::class.java).use {
-      onView(atPosition(R.id.skill_recycler_view,0)).perform(click())
-      onView(atPosition(R.id.skill_recycler_view,0)).perform(click())
+      onView(bindableAdapterTest.atPosition(R.id.skill_recycler_view,0)).perform(click())
+      onView(bindableAdapterTest.atPosition(R.id.skill_recycler_view,0)).perform(click())
       onView(withId(R.id.topic_train_start_button)).check(matches(not(isClickable())))
     }
   }
@@ -101,7 +100,7 @@ class TopicTrainFragmentTest {
   @Test
   fun testTopicTrainFragment_loadFragment_selectSkills_clickStartButton_skillListTransferSuccessfully() {
     activityTestRule.launchActivity(null)
-    onView(atPosition(R.id.skill_recycler_view,0)).perform(click())
+    onView(bindableAdapterTest.atPosition(R.id.skill_recycler_view,0)).perform(click())
     onView(withId(R.id.topic_train_start_button)).perform(click())
     intended(hasComponent(QuestionPlayerActivity::class.java.name))
     intended(hasExtra(QuestionPlayerActivity.getIntentKey(), skillIdList))
@@ -110,9 +109,9 @@ class TopicTrainFragmentTest {
   @Test
   fun testTopicTrainFragment_loadFragment_selectSkills_configurationChange_skillsAreSelected() {
     activityTestRule.launchActivity(null)
-    onView(atPosition(R.id.skill_recycler_view,0)).perform(click())
+    onView(bindableAdapterTest.atPosition(R.id.skill_recycler_view,0)).perform(click())
     activityTestRule.activity.requestedOrientation = ActivityInfo.SCREEN_ORIENTATION_LANDSCAPE
-    onView(atPositionOnView(R.id.skill_recycler_view, 0, R.id.skill_check_box)).check(matches(isChecked()))
+    onView(bindableAdapterTest.atPositionOnView(R.id.skill_recycler_view,0, R.id.skill_check_box)).check(matches(isChecked()))
   }
 
   @Test
@@ -126,7 +125,7 @@ class TopicTrainFragmentTest {
   @Test
   fun testTopicTrainFragment_loadFragment_selectSkills_configurationChange_startButtonRemainsActive() {
     activityTestRule.launchActivity(null)
-    onView(atPosition(R.id.skill_recycler_view,0)).perform(click())
+    onView(bindableAdapterTest.atPosition(R.id.skill_recycler_view,0)).perform(click())
     activityTestRule.activity.requestedOrientation = ActivityInfo.SCREEN_ORIENTATION_LANDSCAPE
     onView(withId(R.id.topic_train_start_button)).check(matches(isClickable()))
   }

From 1b446ff3bcdac12048899deef4dee4dbe34216c5 Mon Sep 17 00:00:00 2001
From: Rajat Talesra <talesra@talesra-macbookpro.roam.corp.google.com>
Date: Tue, 15 Oct 2019 13:17:21 +0530
Subject: [PATCH 25/28] Nit changes

---
 .../questionplayer/QuestionPlayerActivity.kt  |  2 +-
 .../app/recyclerview/BindableAdapterTest.kt   | 52 ---------------
 .../app/recyclerview/RecyclerViewMatcher.kt   | 66 +++++++++++++++++++
 .../app/topic/train/TopicTrainFragmentTest.kt | 27 ++++----
 4 files changed, 80 insertions(+), 67 deletions(-)
 create mode 100644 app/src/sharedTest/java/org/oppia/app/recyclerview/RecyclerViewMatcher.kt

diff --git a/app/src/main/java/org/oppia/app/topic/questionplayer/QuestionPlayerActivity.kt b/app/src/main/java/org/oppia/app/topic/questionplayer/QuestionPlayerActivity.kt
index 38ffaa98ed5..99113fcfe80 100644
--- a/app/src/main/java/org/oppia/app/topic/questionplayer/QuestionPlayerActivity.kt
+++ b/app/src/main/java/org/oppia/app/topic/questionplayer/QuestionPlayerActivity.kt
@@ -28,7 +28,7 @@ class QuestionPlayerActivity : InjectableAppCompatActivity() {
       return intent
     }
 
-    fun getIntentKey():String{
+    fun getIntentKey(): String {
       return QUESTION_PLAYER_ACTIVITY_SKILL_ID_LIST_ARGUMENT_KEY
     }
   }
diff --git a/app/src/sharedTest/java/org/oppia/app/recyclerview/BindableAdapterTest.kt b/app/src/sharedTest/java/org/oppia/app/recyclerview/BindableAdapterTest.kt
index d9c8db7b657..f9d694bf951 100644
--- a/app/src/sharedTest/java/org/oppia/app/recyclerview/BindableAdapterTest.kt
+++ b/app/src/sharedTest/java/org/oppia/app/recyclerview/BindableAdapterTest.kt
@@ -1,6 +1,5 @@
 package org.oppia.app.recyclerview
 
-import android.content.res.Resources
 import android.view.LayoutInflater
 import android.view.ViewGroup
 import android.widget.TextView
@@ -31,7 +30,6 @@ import androidx.test.espresso.matcher.BoundedMatcher
 import android.view.View
 import org.hamcrest.Description
 import org.hamcrest.Matcher
-import org.hamcrest.TypeSafeMatcher
 import org.oppia.app.databinding.TestTextViewForIntWithDataBindingBinding
 import org.oppia.app.databinding.TestTextViewForStringWithDataBindingBinding
 
@@ -330,54 +328,4 @@ class BindableAdapterTest {
       }
     }
   }
-
-  /**
-   * This function returns a Matcher for an item inside RecyclerView from a specified position.
-   */
-  fun atPosition(recyclerViewId: Int, position: Int): Matcher<View> {
-    return atPositionOnView(recyclerViewId, position, -1)
-  }
-
-  /**
-   * This function returns a Matcher for a specific view within the item inside RecyclerView from a specified position.
-   */
-  fun atPositionOnView(recyclerViewId: Int, position: Int, targetViewId: Int): Matcher<View> {
-    return object : TypeSafeMatcher<View>() {
-      var resources: Resources? = null
-      var childView: View? = null
-
-      override fun describeTo(description: Description) {
-        var idDescription = Integer.toString(recyclerViewId)
-        if (this.resources != null) {
-          idDescription = try {
-            this.resources!!.getResourceName(recyclerViewId)
-          } catch (var4: Resources.NotFoundException) {
-            String.format(
-              "%s (resource name not found)",
-              recyclerViewId
-            )
-          }
-        }
-        description.appendText("with id: $idDescription")
-      }
-
-      public override fun matchesSafely(view: View): Boolean {
-        this.resources = view.resources
-        if (childView == null) {
-          val recyclerView = view.rootView.findViewById<View>(recyclerViewId) as RecyclerView
-          if (recyclerView.id == recyclerViewId) {
-            childView = recyclerView.findViewHolderForAdapterPosition(position)!!.itemView
-          } else {
-            return false
-          }
-        }
-        return if (targetViewId == -1) {
-          view === childView
-        } else {
-          val targetView = childView!!.findViewById<View>(targetViewId)
-          view === targetView
-        }
-      }
-    }
-  }
 }
diff --git a/app/src/sharedTest/java/org/oppia/app/recyclerview/RecyclerViewMatcher.kt b/app/src/sharedTest/java/org/oppia/app/recyclerview/RecyclerViewMatcher.kt
new file mode 100644
index 00000000000..2c51333a942
--- /dev/null
+++ b/app/src/sharedTest/java/org/oppia/app/recyclerview/RecyclerViewMatcher.kt
@@ -0,0 +1,66 @@
+package org.oppia.app.recyclerview
+
+import android.content.res.Resources
+import android.view.View
+import androidx.recyclerview.widget.RecyclerView
+import org.hamcrest.Description
+import org.hamcrest.Matcher
+import org.hamcrest.TypeSafeMatcher
+
+// Reference Link: https://github.com/dannyroa/espresso-samples/blob/master/RecyclerView/app/src/androidTest/java/com/dannyroa/espresso_samples/recyclerview/RecyclerViewMatcher.java
+class RecyclerViewMatcher {
+
+  companion object {
+
+    /**
+     * This function returns a Matcher for an item inside RecyclerView from a specified position.
+     */
+    fun atPosition(recyclerViewId: Int, position: Int): Matcher<View> {
+      return atPositionOnView(recyclerViewId, position, -1)
+    }
+
+    /**
+     * This function returns a Matcher for a specific view within the item inside RecyclerView from a specified position.
+     */
+    fun atPositionOnView(recyclerViewId: Int, position: Int, targetViewId: Int): Matcher<View> {
+      return object : TypeSafeMatcher<View>() {
+        var resources: Resources? = null
+        var childView: View? = null
+
+        override fun describeTo(description: Description) {
+          var idDescription = Integer.toString(recyclerViewId)
+          if (this.resources != null) {
+            idDescription = try {
+              this.resources!!.getResourceName(recyclerViewId)
+            } catch (var4: Resources.NotFoundException) {
+              String.format(
+                "%s (resource name not found)",
+                recyclerViewId
+              )
+            }
+          }
+          description.appendText("with id: $idDescription")
+        }
+
+        public override fun matchesSafely(view: View): Boolean {
+          this.resources = view.resources
+          if (childView == null) {
+            val recyclerView = view.rootView.findViewById<View>(recyclerViewId) as RecyclerView
+            if (recyclerView.id == recyclerViewId) {
+              childView = recyclerView.findViewHolderForAdapterPosition(position)!!.itemView
+            } else {
+              return false
+            }
+          }
+          return if (targetViewId == -1) {
+            view === childView
+          } else {
+            val targetView = childView!!.findViewById<View>(targetViewId)
+            view === targetView
+          }
+        }
+      }
+    }
+
+  }
+}
diff --git a/app/src/sharedTest/java/org/oppia/app/topic/train/TopicTrainFragmentTest.kt b/app/src/sharedTest/java/org/oppia/app/topic/train/TopicTrainFragmentTest.kt
index 0916dda813d..08177240703 100644
--- a/app/src/sharedTest/java/org/oppia/app/topic/train/TopicTrainFragmentTest.kt
+++ b/app/src/sharedTest/java/org/oppia/app/topic/train/TopicTrainFragmentTest.kt
@@ -34,7 +34,7 @@ import org.junit.After
 import org.junit.Before
 import org.junit.Rule
 import androidx.test.rule.ActivityTestRule
-import org.oppia.app.recyclerview.BindableAdapterTest
+import org.oppia.app.recyclerview.RecyclerViewMatcher
 import org.oppia.app.topic.questionplayer.QuestionPlayerActivity
 
 /** Tests for [TopicTrainFragment]. */
@@ -42,7 +42,6 @@ import org.oppia.app.topic.questionplayer.QuestionPlayerActivity
 class TopicTrainFragmentTest {
 
   private var skillIdList = ArrayList<String>()
-  private val bindableAdapterTest:BindableAdapterTest = BindableAdapterTest()
 
   @get:Rule
   var activityTestRule: ActivityTestRule<TopicActivity> = ActivityTestRule(
@@ -59,7 +58,7 @@ class TopicTrainFragmentTest {
   fun testTopicTrainFragment_loadFragment_displaySkills_startButtonIsInactive() {
     ActivityScenario.launch(TopicActivity::class.java).use {
       onView(withId(R.id.master_skills_text_view)).check(matches(withText(R.string.topic_train_master_these_skills)))
-      onView(bindableAdapterTest.atPosition(R.id.skill_recycler_view,0)).check(matches(hasDescendant(withId(R.id.skill_check_box))))
+      onView(RecyclerViewMatcher.atPosition(R.id.skill_recycler_view,0)).check(matches(hasDescendant(withId(R.id.skill_check_box))))
       onView(withId(R.id.topic_train_start_button)).check(matches(not(isClickable())))
     }
   }
@@ -67,15 +66,15 @@ class TopicTrainFragmentTest {
   @Test
   fun testTopicTrainFragment_loadFragment_selectSkills_isSuccessful() {
     ActivityScenario.launch(TopicActivity::class.java).use {
-      onView(bindableAdapterTest.atPosition(R.id.skill_recycler_view,0)).perform(click())
-      onView(bindableAdapterTest.atPosition(R.id.skill_recycler_view,1)).perform(click())
+      onView(RecyclerViewMatcher.atPosition(R.id.skill_recycler_view,0)).perform(click())
+      onView(RecyclerViewMatcher.atPosition(R.id.skill_recycler_view,1)).perform(click())
     }
   }
 
   @Test
   fun testTopicTrainFragment_loadFragment_selectSkills_startButtonIsActive() {
     ActivityScenario.launch(TopicActivity::class.java).use {
-      onView(bindableAdapterTest.atPosition(R.id.skill_recycler_view,0)).perform(click())
+      onView(RecyclerViewMatcher.atPosition(R.id.skill_recycler_view,0)).perform(click())
       onView(withId(R.id.topic_train_start_button)).check(matches(isClickable()))
     }
   }
@@ -83,16 +82,16 @@ class TopicTrainFragmentTest {
   @Test
   fun testTopicTrainFragment_loadFragment_selectSkills_deselectSkills_isSuccessful() {
     ActivityScenario.launch(TopicActivity::class.java).use {
-      onView(bindableAdapterTest.atPosition(R.id.skill_recycler_view,0)).perform(click())
-      onView(bindableAdapterTest.atPosition(R.id.skill_recycler_view,0)).perform(click())
+      onView(RecyclerViewMatcher.atPosition(R.id.skill_recycler_view,0)).perform(click())
+      onView(RecyclerViewMatcher.atPosition(R.id.skill_recycler_view,0)).perform(click())
     }
   }
 
   @Test
   fun testTopicTrainFragment_loadFragment_selectSkills_deselectSkills_startButtonIsInactive() {
     ActivityScenario.launch(TopicActivity::class.java).use {
-      onView(bindableAdapterTest.atPosition(R.id.skill_recycler_view,0)).perform(click())
-      onView(bindableAdapterTest.atPosition(R.id.skill_recycler_view,0)).perform(click())
+      onView(RecyclerViewMatcher.atPosition(R.id.skill_recycler_view,0)).perform(click())
+      onView(RecyclerViewMatcher.atPosition(R.id.skill_recycler_view,0)).perform(click())
       onView(withId(R.id.topic_train_start_button)).check(matches(not(isClickable())))
     }
   }
@@ -100,7 +99,7 @@ class TopicTrainFragmentTest {
   @Test
   fun testTopicTrainFragment_loadFragment_selectSkills_clickStartButton_skillListTransferSuccessfully() {
     activityTestRule.launchActivity(null)
-    onView(bindableAdapterTest.atPosition(R.id.skill_recycler_view,0)).perform(click())
+    onView(RecyclerViewMatcher.atPosition(R.id.skill_recycler_view,0)).perform(click())
     onView(withId(R.id.topic_train_start_button)).perform(click())
     intended(hasComponent(QuestionPlayerActivity::class.java.name))
     intended(hasExtra(QuestionPlayerActivity.getIntentKey(), skillIdList))
@@ -109,9 +108,9 @@ class TopicTrainFragmentTest {
   @Test
   fun testTopicTrainFragment_loadFragment_selectSkills_configurationChange_skillsAreSelected() {
     activityTestRule.launchActivity(null)
-    onView(bindableAdapterTest.atPosition(R.id.skill_recycler_view,0)).perform(click())
+    onView(RecyclerViewMatcher.atPosition(R.id.skill_recycler_view,0)).perform(click())
     activityTestRule.activity.requestedOrientation = ActivityInfo.SCREEN_ORIENTATION_LANDSCAPE
-    onView(bindableAdapterTest.atPositionOnView(R.id.skill_recycler_view,0, R.id.skill_check_box)).check(matches(isChecked()))
+    onView(RecyclerViewMatcher.atPositionOnView(R.id.skill_recycler_view,0, R.id.skill_check_box)).check(matches(isChecked()))
   }
 
   @Test
@@ -125,7 +124,7 @@ class TopicTrainFragmentTest {
   @Test
   fun testTopicTrainFragment_loadFragment_selectSkills_configurationChange_startButtonRemainsActive() {
     activityTestRule.launchActivity(null)
-    onView(bindableAdapterTest.atPosition(R.id.skill_recycler_view,0)).perform(click())
+    onView(RecyclerViewMatcher.atPosition(R.id.skill_recycler_view,0)).perform(click())
     activityTestRule.activity.requestedOrientation = ActivityInfo.SCREEN_ORIENTATION_LANDSCAPE
     onView(withId(R.id.topic_train_start_button)).check(matches(isClickable()))
   }

From 2e9a334cf10d27b21e09f452ac8b116a081c9b02 Mon Sep 17 00:00:00 2001
From: Rajat Talesra <talesra@talesra-macbookpro.roam.corp.google.com>
Date: Tue, 15 Oct 2019 13:18:34 +0530
Subject: [PATCH 26/28] Nit changes

---
 .../java/org/oppia/app/recyclerview/RecyclerViewMatcher.kt     | 3 ---
 1 file changed, 3 deletions(-)

diff --git a/app/src/sharedTest/java/org/oppia/app/recyclerview/RecyclerViewMatcher.kt b/app/src/sharedTest/java/org/oppia/app/recyclerview/RecyclerViewMatcher.kt
index 2c51333a942..92296136d1d 100644
--- a/app/src/sharedTest/java/org/oppia/app/recyclerview/RecyclerViewMatcher.kt
+++ b/app/src/sharedTest/java/org/oppia/app/recyclerview/RecyclerViewMatcher.kt
@@ -9,9 +9,7 @@ import org.hamcrest.TypeSafeMatcher
 
 // Reference Link: https://github.com/dannyroa/espresso-samples/blob/master/RecyclerView/app/src/androidTest/java/com/dannyroa/espresso_samples/recyclerview/RecyclerViewMatcher.java
 class RecyclerViewMatcher {
-
   companion object {
-
     /**
      * This function returns a Matcher for an item inside RecyclerView from a specified position.
      */
@@ -61,6 +59,5 @@ class RecyclerViewMatcher {
         }
       }
     }
-
   }
 }

From 5b9d0ddffcaa5ea3a2d05651f8cf9159ce648afb Mon Sep 17 00:00:00 2001
From: Rajat Talesra <talesra@talesra-macbookpro.roam.corp.google.com>
Date: Fri, 18 Oct 2019 11:03:34 +0530
Subject: [PATCH 27/28] Test cases

---
 .../app/recyclerview/BindableAdapterTest.kt   | 57 ++++++-------------
 .../app/topic/train/TopicTrainFragmentTest.kt | 27 ++++-----
 2 files changed, 32 insertions(+), 52 deletions(-)

diff --git a/app/src/sharedTest/java/org/oppia/app/recyclerview/BindableAdapterTest.kt b/app/src/sharedTest/java/org/oppia/app/recyclerview/BindableAdapterTest.kt
index f9d694bf951..4b20747e0d0 100644
--- a/app/src/sharedTest/java/org/oppia/app/recyclerview/BindableAdapterTest.kt
+++ b/app/src/sharedTest/java/org/oppia/app/recyclerview/BindableAdapterTest.kt
@@ -10,7 +10,6 @@ import androidx.test.core.app.ApplicationProvider
 import androidx.test.espresso.Espresso.onIdle
 import androidx.test.espresso.Espresso.onView
 import androidx.test.espresso.assertion.ViewAssertions.matches
-import androidx.test.espresso.matcher.ViewMatchers.withId
 import androidx.test.espresso.matcher.ViewMatchers.withSubstring
 import androidx.test.espresso.matcher.ViewMatchers.withText
 import androidx.test.ext.junit.runners.AndroidJUnit4
@@ -26,12 +25,9 @@ import org.oppia.app.testing.BindableAdapterTestActivity
 import org.oppia.app.testing.BindableAdapterTestFragment
 import org.oppia.app.testing.BindableAdapterTestFragmentPresenter
 import org.oppia.app.testing.BindableAdapterTestViewModel
-import androidx.test.espresso.matcher.BoundedMatcher
-import android.view.View
-import org.hamcrest.Description
-import org.hamcrest.Matcher
 import org.oppia.app.databinding.TestTextViewForIntWithDataBindingBinding
 import org.oppia.app.databinding.TestTextViewForStringWithDataBindingBinding
+import org.oppia.app.recyclerview.RecyclerViewMatcher.Companion.atPosition
 
 /** Tests for [BindableAdapter]. */
 @RunWith(AndroidJUnit4::class)
@@ -88,7 +84,7 @@ class BindableAdapterTest {
         assertThat(recyclerView.childCount).isEqualTo(1)
       }
       // Perform onView() verification off the the main thread to avoid deadlocking.
-      onView(withId(R.id.test_recycler_view)).check(matches(atPosition(0, withText(STR_VALUE_0.strValue))))
+      onView(atPosition(R.id.test_recycler_view, 0)).check(matches(withText(STR_VALUE_0.strValue)))
     }
   }
 
@@ -109,9 +105,9 @@ class BindableAdapterTest {
         val recyclerView: RecyclerView = getTestFragment(activity).view!!.findViewById(R.id.test_recycler_view)
         assertThat(recyclerView.childCount).isEqualTo(3)
       }
-      onView(withId(R.id.test_recycler_view)).check(matches(atPosition(0, withText(STR_VALUE_1.strValue))))
-      onView(withId(R.id.test_recycler_view)).check(matches(atPosition(1, withText(STR_VALUE_0.strValue))))
-      onView(withId(R.id.test_recycler_view)).check(matches(atPosition(2, withText(STR_VALUE_2.strValue))))
+      onView(atPosition(R.id.test_recycler_view, 0)).check(matches(withText(STR_VALUE_1.strValue)))
+      onView(atPosition(R.id.test_recycler_view, 1)).check(matches(withText(STR_VALUE_0.strValue)))
+      onView(atPosition(R.id.test_recycler_view, 2)).check(matches(withText(STR_VALUE_2.strValue)))
     }
   }
 
@@ -133,11 +129,10 @@ class BindableAdapterTest {
         val recyclerView: RecyclerView = getTestFragment(activity).view!!.findViewById(R.id.test_recycler_view)
         assertThat(recyclerView.childCount).isEqualTo(3)
       }
-      onView(withId(R.id.test_recycler_view)).check(matches(atPosition(0, withText(STR_VALUE_1.strValue))))
-      onView(withId(R.id.test_recycler_view))
-        .check(matches(atPosition(1, withSubstring(INT_VALUE_0.intValue.toString()))))
-      onView(withId(R.id.test_recycler_view))
-        .check(matches(atPosition(2, withSubstring(INT_VALUE_1.intValue.toString()))))
+
+      onView(atPosition(R.id.test_recycler_view, 0)).check(matches(withText(STR_VALUE_1.strValue)))
+      onView(atPosition(R.id.test_recycler_view, 1)).check(matches(withSubstring(INT_VALUE_0.intValue.toString())))
+      onView(atPosition(R.id.test_recycler_view, 2)).check(matches(withSubstring(INT_VALUE_1.intValue.toString())))
     }
   }
 
@@ -159,7 +154,7 @@ class BindableAdapterTest {
         assertThat(recyclerView.childCount).isEqualTo(1)
       }
       // Perform onView() verification off the the main thread to avoid deadlocking.
-      onView(withId(R.id.test_recycler_view)).check(matches(atPosition(0, withText(STR_VALUE_0.strValue))))
+      onView(atPosition(R.id.test_recycler_view, 0)).check(matches(withText(STR_VALUE_0.strValue)))
     }
   }
 
@@ -180,9 +175,10 @@ class BindableAdapterTest {
         val recyclerView: RecyclerView = getTestFragment(activity).view!!.findViewById(R.id.test_recycler_view)
         assertThat(recyclerView.childCount).isEqualTo(3)
       }
-      onView(withId(R.id.test_recycler_view)).check(matches(atPosition(0, withText(STR_VALUE_1.strValue))))
-      onView(withId(R.id.test_recycler_view)).check(matches(atPosition(1, withText(STR_VALUE_0.strValue))))
-      onView(withId(R.id.test_recycler_view)).check(matches(atPosition(2, withText(STR_VALUE_2.strValue))))
+
+      onView(atPosition(R.id.test_recycler_view, 0)).check(matches(withText(STR_VALUE_1.strValue)))
+      onView(atPosition(R.id.test_recycler_view, 1)).check(matches(withText(STR_VALUE_0.strValue)))
+      onView(atPosition(R.id.test_recycler_view, 2)).check(matches(withText(STR_VALUE_2.strValue)))
     }
   }
 
@@ -204,11 +200,10 @@ class BindableAdapterTest {
         val recyclerView: RecyclerView = getTestFragment(activity).view!!.findViewById(R.id.test_recycler_view)
         assertThat(recyclerView.childCount).isEqualTo(3)
       }
-      onView(withId(R.id.test_recycler_view)).check(matches(atPosition(0, withText(STR_VALUE_1.strValue))))
-      onView(withId(R.id.test_recycler_view))
-        .check(matches(atPosition(1, withSubstring(INT_VALUE_0.intValue.toString()))))
-      onView(withId(R.id.test_recycler_view))
-        .check(matches(atPosition(2, withSubstring(INT_VALUE_1.intValue.toString()))))
+
+      onView(atPosition(R.id.test_recycler_view, 0)).check(matches(withText(STR_VALUE_1.strValue)))
+      onView(atPosition(R.id.test_recycler_view, 1)).check(matches(withSubstring(INT_VALUE_0.intValue.toString())))
+      onView(atPosition(R.id.test_recycler_view, 2)).check(matches(withSubstring(INT_VALUE_1.intValue.toString())))
     }
   }
 
@@ -312,20 +307,4 @@ class BindableAdapterTest {
     // This must be done off the main thread for Espresso otherwise it deadlocks.
     onIdle()
   }
-
-  // TODO(#89): Move this to a consolidated test library.
-  // https://stackoverflow.com/a/34795431
-  fun atPosition(position: Int, itemMatcher: Matcher<View>): Matcher<View> {
-    return object : BoundedMatcher<View, RecyclerView>(RecyclerView::class.java) {
-      override fun describeTo(description: Description) {
-        description.appendText("has item at position $position: ")
-        itemMatcher.describeTo(description)
-      }
-
-      override fun matchesSafely(view: RecyclerView): Boolean {
-        val viewHolder = view.findViewHolderForAdapterPosition(position) ?: return false
-        return itemMatcher.matches(viewHolder.itemView)
-      }
-    }
-  }
 }
diff --git a/app/src/sharedTest/java/org/oppia/app/topic/train/TopicTrainFragmentTest.kt b/app/src/sharedTest/java/org/oppia/app/topic/train/TopicTrainFragmentTest.kt
index 08177240703..1f6e9be3820 100644
--- a/app/src/sharedTest/java/org/oppia/app/topic/train/TopicTrainFragmentTest.kt
+++ b/app/src/sharedTest/java/org/oppia/app/topic/train/TopicTrainFragmentTest.kt
@@ -34,7 +34,8 @@ import org.junit.After
 import org.junit.Before
 import org.junit.Rule
 import androidx.test.rule.ActivityTestRule
-import org.oppia.app.recyclerview.RecyclerViewMatcher
+import org.oppia.app.recyclerview.RecyclerViewMatcher.Companion.atPosition
+import org.oppia.app.recyclerview.RecyclerViewMatcher.Companion.atPositionOnView
 import org.oppia.app.topic.questionplayer.QuestionPlayerActivity
 
 /** Tests for [TopicTrainFragment]. */
@@ -58,7 +59,7 @@ class TopicTrainFragmentTest {
   fun testTopicTrainFragment_loadFragment_displaySkills_startButtonIsInactive() {
     ActivityScenario.launch(TopicActivity::class.java).use {
       onView(withId(R.id.master_skills_text_view)).check(matches(withText(R.string.topic_train_master_these_skills)))
-      onView(RecyclerViewMatcher.atPosition(R.id.skill_recycler_view,0)).check(matches(hasDescendant(withId(R.id.skill_check_box))))
+      onView(atPosition(R.id.skill_recycler_view,0)).check(matches(hasDescendant(withId(R.id.skill_check_box))))
       onView(withId(R.id.topic_train_start_button)).check(matches(not(isClickable())))
     }
   }
@@ -66,15 +67,15 @@ class TopicTrainFragmentTest {
   @Test
   fun testTopicTrainFragment_loadFragment_selectSkills_isSuccessful() {
     ActivityScenario.launch(TopicActivity::class.java).use {
-      onView(RecyclerViewMatcher.atPosition(R.id.skill_recycler_view,0)).perform(click())
-      onView(RecyclerViewMatcher.atPosition(R.id.skill_recycler_view,1)).perform(click())
+      onView(atPosition(R.id.skill_recycler_view,0)).perform(click())
+      onView(atPosition(R.id.skill_recycler_view,1)).perform(click())
     }
   }
 
   @Test
   fun testTopicTrainFragment_loadFragment_selectSkills_startButtonIsActive() {
     ActivityScenario.launch(TopicActivity::class.java).use {
-      onView(RecyclerViewMatcher.atPosition(R.id.skill_recycler_view,0)).perform(click())
+      onView(atPosition(R.id.skill_recycler_view,0)).perform(click())
       onView(withId(R.id.topic_train_start_button)).check(matches(isClickable()))
     }
   }
@@ -82,16 +83,16 @@ class TopicTrainFragmentTest {
   @Test
   fun testTopicTrainFragment_loadFragment_selectSkills_deselectSkills_isSuccessful() {
     ActivityScenario.launch(TopicActivity::class.java).use {
-      onView(RecyclerViewMatcher.atPosition(R.id.skill_recycler_view,0)).perform(click())
-      onView(RecyclerViewMatcher.atPosition(R.id.skill_recycler_view,0)).perform(click())
+      onView(atPosition(R.id.skill_recycler_view,0)).perform(click())
+      onView(atPosition(R.id.skill_recycler_view,0)).perform(click())
     }
   }
 
   @Test
   fun testTopicTrainFragment_loadFragment_selectSkills_deselectSkills_startButtonIsInactive() {
     ActivityScenario.launch(TopicActivity::class.java).use {
-      onView(RecyclerViewMatcher.atPosition(R.id.skill_recycler_view,0)).perform(click())
-      onView(RecyclerViewMatcher.atPosition(R.id.skill_recycler_view,0)).perform(click())
+      onView(atPosition(R.id.skill_recycler_view,0)).perform(click())
+      onView(atPosition(R.id.skill_recycler_view,0)).perform(click())
       onView(withId(R.id.topic_train_start_button)).check(matches(not(isClickable())))
     }
   }
@@ -99,7 +100,7 @@ class TopicTrainFragmentTest {
   @Test
   fun testTopicTrainFragment_loadFragment_selectSkills_clickStartButton_skillListTransferSuccessfully() {
     activityTestRule.launchActivity(null)
-    onView(RecyclerViewMatcher.atPosition(R.id.skill_recycler_view,0)).perform(click())
+    onView(atPosition(R.id.skill_recycler_view,0)).perform(click())
     onView(withId(R.id.topic_train_start_button)).perform(click())
     intended(hasComponent(QuestionPlayerActivity::class.java.name))
     intended(hasExtra(QuestionPlayerActivity.getIntentKey(), skillIdList))
@@ -108,9 +109,9 @@ class TopicTrainFragmentTest {
   @Test
   fun testTopicTrainFragment_loadFragment_selectSkills_configurationChange_skillsAreSelected() {
     activityTestRule.launchActivity(null)
-    onView(RecyclerViewMatcher.atPosition(R.id.skill_recycler_view,0)).perform(click())
+    onView(atPosition(R.id.skill_recycler_view,0)).perform(click())
     activityTestRule.activity.requestedOrientation = ActivityInfo.SCREEN_ORIENTATION_LANDSCAPE
-    onView(RecyclerViewMatcher.atPositionOnView(R.id.skill_recycler_view,0, R.id.skill_check_box)).check(matches(isChecked()))
+    onView(atPositionOnView(R.id.skill_recycler_view,0, R.id.skill_check_box)).check(matches(isChecked()))
   }
 
   @Test
@@ -124,7 +125,7 @@ class TopicTrainFragmentTest {
   @Test
   fun testTopicTrainFragment_loadFragment_selectSkills_configurationChange_startButtonRemainsActive() {
     activityTestRule.launchActivity(null)
-    onView(RecyclerViewMatcher.atPosition(R.id.skill_recycler_view,0)).perform(click())
+    onView(atPosition(R.id.skill_recycler_view,0)).perform(click())
     activityTestRule.activity.requestedOrientation = ActivityInfo.SCREEN_ORIENTATION_LANDSCAPE
     onView(withId(R.id.topic_train_start_button)).check(matches(isClickable()))
   }

From 8a5f22f411af7106c15297f0c10f6076a7e5c971 Mon Sep 17 00:00:00 2001
From: Rajat Talesra <talesra@talesra-macbookpro.roam.corp.google.com>
Date: Fri, 18 Oct 2019 14:25:33 +0530
Subject: [PATCH 28/28] Test case updated

---
 .../app/recyclerview/BindableAdapterTest.kt   |  1 +
 .../app/topic/train/TopicTrainFragmentTest.kt | 48 +++++++++++--------
 2 files changed, 30 insertions(+), 19 deletions(-)

diff --git a/app/src/sharedTest/java/org/oppia/app/recyclerview/BindableAdapterTest.kt b/app/src/sharedTest/java/org/oppia/app/recyclerview/BindableAdapterTest.kt
index 4b20747e0d0..3b93aea5741 100644
--- a/app/src/sharedTest/java/org/oppia/app/recyclerview/BindableAdapterTest.kt
+++ b/app/src/sharedTest/java/org/oppia/app/recyclerview/BindableAdapterTest.kt
@@ -45,6 +45,7 @@ class BindableAdapterTest {
     // Ensure that the bindable fragment's test state is properly reset each time.
     BindableAdapterTestFragmentPresenter.testBindableAdapter = null
   }
+
   @After
   fun tearDown() {
     // Ensure that the bindable fragment's test state is properly cleaned up.
diff --git a/app/src/sharedTest/java/org/oppia/app/topic/train/TopicTrainFragmentTest.kt b/app/src/sharedTest/java/org/oppia/app/topic/train/TopicTrainFragmentTest.kt
index 1f6e9be3820..4dea2d9763e 100644
--- a/app/src/sharedTest/java/org/oppia/app/topic/train/TopicTrainFragmentTest.kt
+++ b/app/src/sharedTest/java/org/oppia/app/topic/train/TopicTrainFragmentTest.kt
@@ -2,7 +2,7 @@ package org.oppia.app.topic.train
 
 import android.app.Application
 import android.content.Context
-import android.content.pm.ActivityInfo
+import android.content.res.Configuration
 import androidx.test.core.app.ActivityScenario
 import androidx.test.espresso.Espresso.onView
 import androidx.test.espresso.action.ViewActions.click
@@ -44,6 +44,8 @@ class TopicTrainFragmentTest {
 
   private var skillIdList = ArrayList<String>()
 
+  private lateinit var activityScenario: ActivityScenario<TopicActivity>
+
   @get:Rule
   var activityTestRule: ActivityTestRule<TopicActivity> = ActivityTestRule(
     TopicActivity::class.java, /* initialTouchMode= */ true, /* launchActivity= */ false
@@ -51,6 +53,8 @@ class TopicTrainFragmentTest {
 
   @Before
   fun setUp() {
+    activityScenario = ActivityScenario.launch(TopicActivity::class.java)
+
     Intents.init()
     skillIdList.add("test_skill_id_0")
   }
@@ -59,7 +63,7 @@ class TopicTrainFragmentTest {
   fun testTopicTrainFragment_loadFragment_displaySkills_startButtonIsInactive() {
     ActivityScenario.launch(TopicActivity::class.java).use {
       onView(withId(R.id.master_skills_text_view)).check(matches(withText(R.string.topic_train_master_these_skills)))
-      onView(atPosition(R.id.skill_recycler_view,0)).check(matches(hasDescendant(withId(R.id.skill_check_box))))
+      onView(atPosition(R.id.skill_recycler_view, 0)).check(matches(hasDescendant(withId(R.id.skill_check_box))))
       onView(withId(R.id.topic_train_start_button)).check(matches(not(isClickable())))
     }
   }
@@ -67,15 +71,15 @@ class TopicTrainFragmentTest {
   @Test
   fun testTopicTrainFragment_loadFragment_selectSkills_isSuccessful() {
     ActivityScenario.launch(TopicActivity::class.java).use {
-      onView(atPosition(R.id.skill_recycler_view,0)).perform(click())
-      onView(atPosition(R.id.skill_recycler_view,1)).perform(click())
+      onView(atPosition(R.id.skill_recycler_view, 0)).perform(click())
+      onView(atPosition(R.id.skill_recycler_view, 1)).perform(click())
     }
   }
 
   @Test
   fun testTopicTrainFragment_loadFragment_selectSkills_startButtonIsActive() {
     ActivityScenario.launch(TopicActivity::class.java).use {
-      onView(atPosition(R.id.skill_recycler_view,0)).perform(click())
+      onView(atPosition(R.id.skill_recycler_view, 0)).perform(click())
       onView(withId(R.id.topic_train_start_button)).check(matches(isClickable()))
     }
   }
@@ -83,16 +87,16 @@ class TopicTrainFragmentTest {
   @Test
   fun testTopicTrainFragment_loadFragment_selectSkills_deselectSkills_isSuccessful() {
     ActivityScenario.launch(TopicActivity::class.java).use {
-      onView(atPosition(R.id.skill_recycler_view,0)).perform(click())
-      onView(atPosition(R.id.skill_recycler_view,0)).perform(click())
+      onView(atPosition(R.id.skill_recycler_view, 0)).perform(click())
+      onView(atPosition(R.id.skill_recycler_view, 0)).perform(click())
     }
   }
 
   @Test
   fun testTopicTrainFragment_loadFragment_selectSkills_deselectSkills_startButtonIsInactive() {
     ActivityScenario.launch(TopicActivity::class.java).use {
-      onView(atPosition(R.id.skill_recycler_view,0)).perform(click())
-      onView(atPosition(R.id.skill_recycler_view,0)).perform(click())
+      onView(atPosition(R.id.skill_recycler_view, 0)).perform(click())
+      onView(atPosition(R.id.skill_recycler_view, 0)).perform(click())
       onView(withId(R.id.topic_train_start_button)).check(matches(not(isClickable())))
     }
   }
@@ -100,7 +104,7 @@ class TopicTrainFragmentTest {
   @Test
   fun testTopicTrainFragment_loadFragment_selectSkills_clickStartButton_skillListTransferSuccessfully() {
     activityTestRule.launchActivity(null)
-    onView(atPosition(R.id.skill_recycler_view,0)).perform(click())
+    onView(atPosition(R.id.skill_recycler_view, 0)).perform(click())
     onView(withId(R.id.topic_train_start_button)).perform(click())
     intended(hasComponent(QuestionPlayerActivity::class.java.name))
     intended(hasExtra(QuestionPlayerActivity.getIntentKey(), skillIdList))
@@ -108,25 +112,31 @@ class TopicTrainFragmentTest {
 
   @Test
   fun testTopicTrainFragment_loadFragment_selectSkills_configurationChange_skillsAreSelected() {
-    activityTestRule.launchActivity(null)
-    onView(atPosition(R.id.skill_recycler_view,0)).perform(click())
-    activityTestRule.activity.requestedOrientation = ActivityInfo.SCREEN_ORIENTATION_LANDSCAPE
-    onView(atPositionOnView(R.id.skill_recycler_view,0, R.id.skill_check_box)).check(matches(isChecked()))
+    onView(atPosition(R.id.skill_recycler_view, 0)).perform(click())
+    activityScenario.onActivity { activity ->
+      activity.requestedOrientation = Configuration.ORIENTATION_LANDSCAPE
+    }
+    activityScenario.recreate()
+    onView(atPositionOnView(R.id.skill_recycler_view, 0, R.id.skill_check_box)).check(matches(isChecked()))
   }
 
   @Test
   fun testTopicTrainFragment_loadFragment_configurationChange_startButtonRemainsInactive() {
-    activityTestRule.launchActivity(null)
     onView(withId(R.id.topic_train_start_button)).check(matches(not(isClickable())))
-    activityTestRule.activity.requestedOrientation = ActivityInfo.SCREEN_ORIENTATION_LANDSCAPE
+    activityScenario.onActivity { activity ->
+      activity.requestedOrientation = Configuration.ORIENTATION_LANDSCAPE
+    }
+    activityScenario.recreate()
     onView(withId(R.id.topic_train_start_button)).check(matches(not(isClickable())))
   }
 
   @Test
   fun testTopicTrainFragment_loadFragment_selectSkills_configurationChange_startButtonRemainsActive() {
-    activityTestRule.launchActivity(null)
-    onView(atPosition(R.id.skill_recycler_view,0)).perform(click())
-    activityTestRule.activity.requestedOrientation = ActivityInfo.SCREEN_ORIENTATION_LANDSCAPE
+    onView(atPosition(R.id.skill_recycler_view, 0)).perform(click())
+    activityScenario.onActivity { activity ->
+      activity.requestedOrientation = Configuration.ORIENTATION_LANDSCAPE
+    }
+    activityScenario.recreate()
     onView(withId(R.id.topic_train_start_button)).check(matches(isClickable()))
   }