Fix part of #1633: Removed textview reference from RevisionCardViewmo…

…del (#1981)

* Removed textview from RevisionCardViewmodel

- Removed textview reference from RevisionCardViewModel
- Removed explanationLiveData value from RevisionCardViewModel as the
  function that is used to get the charsequence was using view, now the
  code for the same is shifted to RevisionCardFragmentPresenter. So now
  RevisionCardViewModel expose RevisionCardLiveData and presenter
  observe it and then uses the HTML factory to get the char sequence and
  then update the textview
- Removed the usage of explanation livedata from
  revision_card_fragment.xml

* renamed setSubtopicIdAndBinding function and removed extra space & simplified view.text assignment

* Used named arguments 'imageCenterAlign' to have compiler verification

Co-authored-by: Ben Henning <[email protected]>

Co-authored-by: Ben Henning <[email protected]>

app/src/main/java/org/oppia/android/app/topic/revisioncard/RevisionCardFragmentPresenter.kt

@@ -4,11 +4,15 @@ import android.view.LayoutInflater
 import android.view.View
 import android.view.ViewGroup
 import androidx.fragment.app.Fragment
+import androidx.lifecycle.Observer
 import org.oppia.android.app.fragment.FragmentScope
 import org.oppia.android.app.model.EventLog
 import org.oppia.android.app.viewmodel.ViewModelProvider
 import org.oppia.android.databinding.RevisionCardFragmentBinding
 import org.oppia.android.domain.oppialogger.OppiaLogger
+import org.oppia.android.util.gcsresource.DefaultResourceBucketName
+import org.oppia.android.util.parser.HtmlParser
+import org.oppia.android.util.parser.TopicHtmlParserEntityType
 import org.oppia.android.util.system.OppiaClock
 import javax.inject.Inject
 
@@ -18,6 +22,9 @@ class RevisionCardFragmentPresenter @Inject constructor(
   private val fragment: Fragment,
   private val oppiaLogger: OppiaLogger,
   private val oppiaClock: OppiaClock,
+  private val htmlParserFactory: HtmlParser.Factory,
+  @DefaultResourceBucketName private val resourceBucketName: String,
+  @TopicHtmlParserEntityType private val entityType: String,
   private val viewModelProvider: ViewModelProvider<RevisionCardViewModel>
 ) {
 
@@ -36,13 +43,23 @@ class RevisionCardFragmentPresenter @Inject constructor(
     val view = binding.revisionCardExplanationText
     val viewModel = getReviewCardViewModel()
 
-    viewModel.setSubtopicIdAndBinding(topicId, subtopicId, view)
+    viewModel.setTopicAndSubtopicId(topicId, subtopicId)
     logRevisionCardEvent(topicId, subtopicId)
 
     binding.let {
       it.viewModel = viewModel
       it.lifecycleOwner = fragment
     }
+
+    viewModel.revisionCardLiveData.observe(
+      fragment,
+      Observer {
+        view.text = htmlParserFactory.create(
+          resourceBucketName, entityType, topicId, imageCenterAlign = true
+        ).parseOppiaHtml(it.pageContents.html, view)
+      }
+    )
+
     return binding.root
   }
 

app/src/main/java/org/oppia/android/app/topic/revisioncard/RevisionCardViewModel.kt

@@ -1,7 +1,6 @@
 package org.oppia.android.app.topic.revisioncard
 
 import android.view.View
-import android.widget.TextView
 import androidx.appcompat.app.AppCompatActivity
 import androidx.lifecycle.LiveData
 import androidx.lifecycle.Transformations
@@ -10,73 +9,60 @@ import org.oppia.android.app.model.RevisionCard
 import org.oppia.android.app.viewmodel.ObservableViewModel
 import org.oppia.android.domain.topic.TopicController
 import org.oppia.android.util.data.AsyncResult
-import org.oppia.android.util.gcsresource.DefaultResourceBucketName
 import org.oppia.android.util.logging.ConsoleLogger
-import org.oppia.android.util.parser.HtmlParser
-import org.oppia.android.util.parser.TopicHtmlParserEntityType
 import javax.inject.Inject
 
-// TODO(#1633): Fix ViewModel to not depend on View
 /** [ObservableViewModel] for revision card, providing rich text and worked examples */
 @FragmentScope
 class RevisionCardViewModel @Inject constructor(
   activity: AppCompatActivity,
   private val topicController: TopicController,
-  private val logger: ConsoleLogger,
-  private val htmlParserFactory: HtmlParser.Factory,
-  @DefaultResourceBucketName private val resourceBucketName: String,
-  @TopicHtmlParserEntityType private val entityType: String
+  private val logger: ConsoleLogger
 ) : ObservableViewModel() {
   private lateinit var topicId: String
   private var subtopicId: Int = 0
-  private lateinit var view: TextView
 
   private val returnToTopicClickListener: ReturnToTopicClickListener =
     activity as ReturnToTopicClickListener
 
-  val explanationLiveData: LiveData<CharSequence> by lazy {
-    processExplanationLiveData()
+  val revisionCardLiveData: LiveData<RevisionCard> by lazy {
+    processRevisionCardLiveData()
   }
 
   fun clickReturnToTopic(@Suppress("UNUSED_PARAMETER") v: View) {
     returnToTopicClickListener.onReturnToTopicClicked()
   }
 
-  /** Sets the value of topicId, subtopicId and binding before anything else. */
-  fun setSubtopicIdAndBinding(
+  /** Sets the value of topicId, subtopicId before anything else. */
+  fun setTopicAndSubtopicId(
     topicId: String,
-    subtopicId: Int,
-    view: TextView
+    subtopicId: Int
   ) {
     this.topicId = topicId
     this.subtopicId = subtopicId
-    this.view = view
   }
 
   private val revisionCardResultLiveData: LiveData<AsyncResult<RevisionCard>> by lazy {
     topicController.getRevisionCard(topicId, subtopicId)
   }
 
-  private fun processExplanationLiveData(): LiveData<CharSequence> {
-    return Transformations.map(revisionCardResultLiveData, ::processExplanationResult)
+  private fun processRevisionCardLiveData(): LiveData<RevisionCard> {
+    return Transformations.map(revisionCardResultLiveData, ::processRevisionCard)
   }
 
-  private fun processExplanationResult(
+  private fun processRevisionCard(
     revisionCardResult: AsyncResult<RevisionCard>
-  ): CharSequence {
+  ): RevisionCard {
     if (revisionCardResult.isFailure()) {
       logger.e(
         "RevisionCardFragment",
         "Failed to retrieve Revision Card",
         revisionCardResult.getErrorOrNull()!!
       )
     }
-    val revisionCard = revisionCardResult.getOrDefault(
+
+    return revisionCardResult.getOrDefault(
       RevisionCard.getDefaultInstance()
     )
-    return htmlParserFactory.create(
-
-      resourceBucketName, entityType, topicId, /* imageCenterAlign= */ true
-    ).parseOppiaHtml(revisionCard.pageContents.html, view)
   }
 }

app/src/main/res/layout-land/revision_card_fragment.xml

@@ -30,7 +30,6 @@
         android:layout_marginTop="24dp"
         android:layout_marginEnd="52dp"
         android:fontFamily="sans-serif"
-        android:text="@{viewModel.explanationLiveData}"
         android:textColor="@color/oppiaPrimaryText"
         android:textSize="16sp" />
 

app/src/main/res/layout/revision_card_fragment.xml

@@ -30,7 +30,6 @@
         android:layout_marginTop="36dp"
         android:layout_marginEnd="28dp"
         android:fontFamily="sans-serif"
-        android:text="@{viewModel.explanationLiveData}"
         android:textColor="@color/oppiaPrimaryText"
         android:textSize="16sp" />