Fix #1737: Singleton for exploration to handle input for configuration changes

app/src/main/java/org/oppia/android/app/player/state/StateFragment.kt

@@ -129,4 +129,18 @@ class StateFragment :
   fun revealSolution() = stateFragmentPresenter.revealSolution()
 
   fun dismissConceptCard() = stateFragmentPresenter.dismissConceptCard()
+
+  override fun onResume() {
+    super.onResume()
+    stateFragmentPresenter.handleOnResume()
+  }
+
+  override fun onDestroyView() {
+    super.onDestroyView()
+    stateFragmentPresenter.handleDestroyView()
+  }
+
+  override fun setPendingAnswer(userAnswer: UserAnswer) {
+//    TODO("Not yet implemented")
+  }
 }

app/src/main/java/org/oppia/android/app/player/state/StateFragmentPresenter.kt

@@ -1,6 +1,7 @@
 package org.oppia.android.app.player.state
 
 import android.content.Context
+import android.util.Log
 import android.view.LayoutInflater
 import android.view.View
 import android.view.ViewGroup
@@ -32,6 +33,7 @@ import org.oppia.android.app.utility.SplitScreenManager
 import org.oppia.android.app.viewmodel.ViewModelProvider
 import org.oppia.android.databinding.StateFragmentBinding
 import org.oppia.android.domain.exploration.ExplorationProgressController
+import org.oppia.android.domain.state.RetriveUserAnswer
 import org.oppia.android.domain.topic.StoryProgressController
 import org.oppia.android.util.data.AsyncResult
 import org.oppia.android.util.data.DataProviders.Companion.toLiveData
@@ -154,6 +156,7 @@ class StateFragmentPresenter @Inject constructor(
     viewModel.setHintBulbVisibility(false)
     hideKeyboard()
     moveToNextState()
+    RetriveUserAnswer.clearUserAnswer()
   }
 
   fun onNextButtonClicked() = moveToNextState()
@@ -521,4 +524,18 @@ class StateFragmentPresenter @Inject constructor(
       Date().time
     )
   }
+
+  fun handleOnResume() {
+    RetriveUserAnswer.getUserAnswer()?.let {
+      viewModel.setPendingAnswer(it, recyclerViewAssembler::getPendingAnswerHandler)
+      Log.d("testSingleton", "userAnswer -> ${it.answer}")
+      Log.d("testSingleton", "userAnswer -> $it")
+    }
+  }
+
+  fun handleDestroyView() {
+    RetriveUserAnswer.setUserAnswer(
+      viewModel.getPendingAnswer(recyclerViewAssembler::getPendingAnswerHandler)
+    )
+  }
 }

app/src/main/java/org/oppia/android/app/player/state/StateViewModel.kt

@@ -58,6 +58,13 @@ class StateViewModel @Inject constructor() : ObservableViewModel() {
     ) ?: UserAnswer.getDefaultInstance()
   }
 
+  fun setPendingAnswer(
+    userAnswer: UserAnswer,
+    retrieveAnswerHandler: (List<StateItemViewModel>) -> InteractionAnswerHandler?
+  ) {
+    retrieveAnswerHandler(getAnswerItemList())?.setPendingAnswer(userAnswer)
+  }
+
   private fun getPendingAnswerWithoutError(
     answerHandler: InteractionAnswerHandler?
   ): UserAnswer? {

app/src/main/java/org/oppia/android/app/player/state/answerhandling/InteractionAnswerHandler.kt

@@ -26,6 +26,8 @@ interface InteractionAnswerHandler {
   fun getPendingAnswer(): UserAnswer? {
     return null
   }
+
+  fun setPendingAnswer(userAnswer: UserAnswer)
 }
 
 /**

app/src/main/java/org/oppia/android/app/player/state/itemviewmodel/ContinueInteractionViewModel.kt

@@ -37,6 +37,10 @@ class ContinueInteractionViewModel(
       .build()
   }
 
+  override fun setPendingAnswer(userAnswer: UserAnswer) {
+//    TODO("Not yet implemented")
+  }
+
   fun handleButtonClicked() {
     interactionAnswerReceiver.onAnswerReadyForSubmission(getPendingAnswer())
   }

app/src/main/java/org/oppia/android/app/player/state/itemviewmodel/DragAndDropSortInteractionViewModel.kt

@@ -106,6 +106,10 @@ class DragAndDropSortInteractionViewModel(
     return userAnswerBuilder.build()
   }
 
+  override fun setPendingAnswer(userAnswer: UserAnswer) {
+//    TODO("Not yet implemented")
+  }
+
   /** Returns an HTML list containing all of the HTML string elements as items in the list. */
   private fun convertItemsToAnswer(htmlItems: List<StringList>): ListOfSetsOfHtmlStrings {
     return ListOfSetsOfHtmlStrings.newBuilder()

app/src/main/java/org/oppia/android/app/player/state/itemviewmodel/FractionInteractionViewModel.kt

@@ -3,6 +3,7 @@ package org.oppia.android.app.player.state.itemviewmodel
 import android.content.Context
 import android.text.Editable
 import android.text.TextWatcher
+import android.util.Log
 import androidx.databinding.Observable
 import androidx.databinding.ObservableField
 import org.oppia.android.R
@@ -23,7 +24,7 @@ class FractionInteractionViewModel(
   private val interactionAnswerErrorOrAvailabilityCheckReceiver: InteractionAnswerErrorOrAvailabilityCheckReceiver // ktlint-disable max-line-length
 ) : StateItemViewModel(ViewType.FRACTION_INPUT_INTERACTION), InteractionAnswerHandler {
   private var pendingAnswerError: String? = null
-  var answerText: CharSequence = ""
+  var answerText = ObservableField<String>("")
   var isAnswerAvailable = ObservableField<Boolean>(false)
   var errorMessage = ObservableField<String>("")
 
@@ -36,7 +37,7 @@ class FractionInteractionViewModel(
         override fun onPropertyChanged(sender: Observable, propertyId: Int) {
           interactionAnswerErrorOrAvailabilityCheckReceiver.onPendingAnswerErrorOrAvailabilityCheck(
             pendingAnswerError,
-            answerText.isNotEmpty()
+            answerText.get()!!.isNotEmpty()
           )
         }
       }
@@ -46,8 +47,8 @@ class FractionInteractionViewModel(
 
   override fun getPendingAnswer(): UserAnswer {
     val userAnswerBuilder = UserAnswer.newBuilder()
-    if (answerText.isNotEmpty()) {
-      val answerTextString = answerText.toString()
+    if (answerText.get()!!.isNotEmpty()) {
+      val answerTextString = answerText.get().toString()
       userAnswerBuilder.answer = InteractionObject.newBuilder()
         .setFraction(stringToFractionParser.parseFractionFromString(answerTextString))
         .build()
@@ -56,19 +57,24 @@ class FractionInteractionViewModel(
     return userAnswerBuilder.build()
   }
 
+  override fun setPendingAnswer(userAnswer: UserAnswer) {
+    answerText.set(userAnswer.plainAnswer)
+    Log.d("testSingleton", "i've set the value finally it is ${userAnswer.plainAnswer}")
+  }
+
   /** It checks the pending error for the current fraction input, and correspondingly updates the error string based on the specified error category. */
   override fun checkPendingAnswerError(category: AnswerErrorCategory): String? {
-    if (answerText.isNotEmpty()) {
+    if (answerText.get()!!.isNotEmpty()) {
       when (category) {
         AnswerErrorCategory.REAL_TIME ->
           pendingAnswerError =
-            stringToFractionParser.getRealTimeAnswerError(answerText.toString())
+            stringToFractionParser.getRealTimeAnswerError(answerText.get().toString())
               .getErrorMessageFromStringRes(
                 context
               )
         AnswerErrorCategory.SUBMIT_TIME ->
           pendingAnswerError =
-            stringToFractionParser.getSubmitTimeError(answerText.toString())
+            stringToFractionParser.getSubmitTimeError(answerText.get().toString())
               .getErrorMessageFromStringRes(
                 context
               )
@@ -84,12 +90,14 @@ class FractionInteractionViewModel(
       }
 
       override fun onTextChanged(answer: CharSequence, start: Int, before: Int, count: Int) {
-        answerText = answer.toString().trim()
-        val isAnswerTextAvailable = answerText.isNotEmpty()
-        if (isAnswerTextAvailable != isAnswerAvailable.get()) {
-          isAnswerAvailable.set(isAnswerTextAvailable)
+        if (answer.isNotEmpty()) {
+          answerText.set(answer.toString().trim())
+          val isAnswerTextAvailable = answerText.get()!!.isNotEmpty()
+          if (isAnswerTextAvailable != isAnswerAvailable.get()) {
+            isAnswerAvailable.set(isAnswerTextAvailable)
+          }
+          checkPendingAnswerError(AnswerErrorCategory.REAL_TIME)
         }
-        checkPendingAnswerError(AnswerErrorCategory.REAL_TIME)
       }
 
       override fun afterTextChanged(s: Editable) {

app/src/main/java/org/oppia/android/app/player/state/itemviewmodel/ImageRegionSelectionInteractionViewModel.kt

@@ -76,6 +76,10 @@ class ImageRegionSelectionInteractionViewModel(
     return userAnswerBuilder.build()
   }
 
+  override fun setPendingAnswer(userAnswer: UserAnswer) {
+//    TODO("Not yet implemented")
+  }
+
   private fun parseClickOnImage(answerTextString: String): ClickOnImage {
     val region = selectableRegions.find { it.label == answerTextString }
     return ClickOnImage.newBuilder()

app/src/main/java/org/oppia/android/app/player/state/itemviewmodel/NumericInputViewModel.kt

@@ -84,4 +84,8 @@ class NumericInputViewModel(
     }
     return userAnswerBuilder.build()
   }
+
+  override fun setPendingAnswer(userAnswer: UserAnswer) {
+//    TODO("Not yet implemented")
+  }
 }

app/src/main/java/org/oppia/android/app/player/state/itemviewmodel/RatioExpressionInputInteractionViewModel.kt

@@ -34,6 +34,10 @@ class RatioExpressionInputInteractionViewModel(
   private val numberOfTerms =
     interaction.customizationArgsMap["numberOfTerms"]?.signedInt ?: 0
 
+  override fun setPendingAnswer(userAnswer: UserAnswer) {
+//    TODO("Not yet implemented")
+  }
+
   init {
     val callback: Observable.OnPropertyChangedCallback =
       object : Observable.OnPropertyChangedCallback() {

app/src/main/java/org/oppia/android/app/player/state/itemviewmodel/SelectionInteractionViewModel.kt

@@ -85,6 +85,10 @@ class SelectionInteractionViewModel(
     return userAnswerBuilder.build()
   }
 
+  override fun setPendingAnswer(userAnswer: UserAnswer) {
+//    TODO("Not yet implemented")
+  }
+
   /** Returns an HTML list containing all of the HTML string elements as items in the list. */
   private fun convertSelectedItemsToHtmlString(htmlItems: Collection<String>): String {
     return when (htmlItems.size) {

app/src/main/java/org/oppia/android/app/player/state/itemviewmodel/TextInputViewModel.kt

@@ -64,6 +64,10 @@ class TextInputViewModel(
     return userAnswerBuilder.build()
   }
 
+  override fun setPendingAnswer(userAnswer: UserAnswer) {
+//    TODO("Not yet implemented")
+  }
+
   private fun deriveHintText(interaction: Interaction): CharSequence {
     // The default placeholder for text input is empty.
     return interaction.customizationArgsMap["placeholder"]?.subtitledUnicode?.unicodeStr ?: ""

domain/src/main/java/org/oppia/android/domain/state/RetriveUserAnswer.kt

@@ -0,0 +1,25 @@
+package org.oppia.android.domain.state
+
+import org.oppia.android.app.model.UserAnswer
+
+object RetriveUserAnswer {
+  // text and error message for fraction [FractionInteractionView.kt]
+  // list of check boxes as a string and back to check box [SelectionInteractionView.kt]
+  // text and error msg for [NumericInputInteractionView.kt]
+  // text and error message for [RatioInputInteractionView.kt]
+  // text for [TextInputInteractionView.kt]
+  // list for drag & drop [DragDropSortInteractionView.kt]
+  // list for drag & drop with merging [DragDropSortInteractionView.kt]
+  // selected img in the [ImageRegionSelectionInteractionView.kt]
+
+  private var userAnswer: UserAnswer? = null
+
+  fun setUserAnswer(solution: UserAnswer) {
+    this.userAnswer = solution
+  }
+  fun getUserAnswer(): UserAnswer? = userAnswer
+
+  fun clearUserAnswer() {
+    userAnswer = null
+  }
+}