Fixes #4470, #4471, #4472, #4473, #4474, #4708: Handle configuration change using on saved instance

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

@@ -51,6 +51,7 @@ class ImageRegionSelectionInteractionView @JvmOverloads constructor(
   private lateinit var onRegionClicked: OnClickableAreaClickedListener
   private lateinit var imageUrl: String
   private lateinit var clickableAreas: List<ImageWithRegions.LabeledRegion>
+  private lateinit var lastSelectedRegion: ImageWithRegions.LabeledRegion
 
   /**
    * Sets the URL for the image & initiates loading it. This is intended to be called via
@@ -66,6 +67,11 @@ class ImageRegionSelectionInteractionView @JvmOverloads constructor(
     maybeInitializeClickableAreas()
   }
 
+  fun setLastSelectedRegion(lastSelectedRegion: ImageWithRegions.LabeledRegion) {
+    this.lastSelectedRegion = lastSelectedRegion
+    maybeInitializeClickableAreas()
+  }
+
   fun setClickableAreas(clickableAreas: List<ImageWithRegions.LabeledRegion>) {
     this.clickableAreas = clickableAreas
     // Resets the backgrounds for all regions if any have been loaded. This ensures the backgrounds
@@ -120,6 +126,9 @@ class ImageRegionSelectionInteractionView @JvmOverloads constructor(
         clickableAreas
       )
       areasImage.addRegionViews()
+      if (::lastSelectedRegion.isInitialized && lastSelectedRegion.hasRegion()) {
+        areasImage.toggleRegion(lastSelectedRegion, view = null)
+      }
       performAttachment(areasImage)
     }
   }

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

@@ -7,6 +7,8 @@ import androidx.databinding.ObservableList
 import androidx.fragment.app.Fragment
 import androidx.fragment.app.FragmentManager
 import androidx.recyclerview.widget.RecyclerView
+import kotlinx.android.synthetic.main.item_selection_interaction_items.view.*
+import kotlinx.android.synthetic.main.multiple_choice_interaction_items.view.*
 import org.oppia.android.app.model.WrittenTranslationContext
 import org.oppia.android.app.player.state.itemviewmodel.SelectionInteractionContentViewModel
 import org.oppia.android.app.player.state.itemviewmodel.SelectionItemInputType
@@ -28,12 +30,17 @@ class SelectionInteractionView @JvmOverloads constructor(
   attrs: AttributeSet? = null,
   defStyleAttr: Int = 0
 ) : RecyclerView(context, attrs, defStyleAttr) {
-  @field:[Inject ExplorationHtmlParserEntityType] lateinit var entityType: String
-  @field:[Inject DefaultResourceBucketName] lateinit var resourceBucketName: String
+  @field:[Inject ExplorationHtmlParserEntityType]
+  lateinit var entityType: String
+  @field:[Inject DefaultResourceBucketName]
+  lateinit var resourceBucketName: String
 
-  @Inject lateinit var htmlParserFactory: HtmlParser.Factory
-  @Inject lateinit var bindingInterface: ViewBindingShim
-  @Inject lateinit var singleTypeBuilderFactory: BindableAdapter.SingleTypeBuilder.Factory
+  @Inject
+  lateinit var htmlParserFactory: HtmlParser.Factory
+  @Inject
+  lateinit var bindingInterface: ViewBindingShim
+  @Inject
+  lateinit var singleTypeBuilderFactory: BindableAdapter.SingleTypeBuilder.Factory
 
   private lateinit var selectionItemInputType: SelectionItemInputType
   private lateinit var entityId: String
@@ -99,11 +106,17 @@ class SelectionInteractionView @JvmOverloads constructor(
         singleTypeBuilderFactory.create<SelectionInteractionContentViewModel>()
           .registerViewBinder(
             inflateView = { parent ->
-              bindingInterface.provideSelectionInteractionViewInflatedView(
+              val checkBox = bindingInterface.provideSelectionInteractionViewInflatedView(
                 LayoutInflater.from(parent.context),
                 parent,
                 /* attachToParent= */ false
               )
+              if (dataList.map { it.disableAnimation }.any { it }) {
+                checkBox.multiple_choice_radio_button.setOnCheckedChangeListener { view, _ ->
+                  view.jumpDrawablesToCurrentState()
+                }
+              }
+              checkBox
             },
             bindView = { view, viewModel ->
               bindingInterface.provideSelectionInteractionViewModel(
@@ -122,11 +135,17 @@ class SelectionInteractionView @JvmOverloads constructor(
         singleTypeBuilderFactory.create<SelectionInteractionContentViewModel>()
           .registerViewBinder(
             inflateView = { parent ->
-              bindingInterface.provideMultipleChoiceInteractionItemsInflatedView(
+              val radioButton = bindingInterface.provideMultipleChoiceInteractionItemsInflatedView(
                 LayoutInflater.from(parent.context),
                 parent,
                 /* attachToParent= */ false
               )
+              if (dataList.map { it.disableAnimation }.any { it }) {
+                radioButton.multiple_choice_radio_button.setOnCheckedChangeListener { view, _ ->
+                  view.jumpDrawablesToCurrentState()
+                }
+              }
+              radioButton
             },
             bindView = { view, viewModel ->
               bindingInterface.provideMultipleChoiceInteractionItemsViewModel(

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

@@ -8,6 +8,7 @@ import android.view.ViewGroup
 import org.oppia.android.app.fragment.FragmentComponentImpl
 import org.oppia.android.app.fragment.InjectableFragment
 import org.oppia.android.app.model.HelpIndex
+import org.oppia.android.app.model.RawUserAnswer
 import org.oppia.android.app.model.UserAnswer
 import org.oppia.android.app.player.state.answerhandling.InteractionAnswerErrorOrAvailabilityCheckReceiver
 import org.oppia.android.app.player.state.answerhandling.InteractionAnswerHandler
@@ -19,9 +20,15 @@ import org.oppia.android.app.player.state.listener.PreviousResponsesHeaderClickL
 import org.oppia.android.app.player.state.listener.ReturnToTopicNavigationButtonListener
 import org.oppia.android.app.player.state.listener.ShowHintAvailabilityListener
 import org.oppia.android.app.player.state.listener.SubmitNavigationButtonListener
+import org.oppia.android.util.extensions.getProto
 import org.oppia.android.util.extensions.getStringFromBundle
+import org.oppia.android.util.extensions.putProto
 import javax.inject.Inject
 
+private const val STATE_FRAGMENT_RAW_USER_ANSWER_KEY = "StateFragment.raw_user_answer"
+private const val STATE_FRAGMENT_ARE_PREVIOUS_RESPONSES_HEADER_EXPANDED_KEY =
+  "StateFragment.are_previous_responses_header_expanded"
+
 /** Fragment that represents the current state of an exploration. */
 class StateFragment :
   InjectableFragment(),
@@ -79,12 +86,20 @@ class StateFragment :
     val storyId = arguments!!.getStringFromBundle(STATE_FRAGMENT_STORY_ID_ARGUMENT_KEY)!!
     val explorationId =
       arguments!!.getStringFromBundle(STATE_FRAGMENT_EXPLORATION_ID_ARGUMENT_KEY)!!
+    val rawUserAnswer = savedInstanceState?.getProto(
+      STATE_FRAGMENT_RAW_USER_ANSWER_KEY, RawUserAnswer.getDefaultInstance()
+    ) ?: RawUserAnswer.getDefaultInstance()
+    val arePreviousResponsesExpanded =
+      savedInstanceState?.getBoolean(STATE_FRAGMENT_ARE_PREVIOUS_RESPONSES_HEADER_EXPANDED_KEY)
+        ?: false
     return stateFragmentPresenter.handleCreateView(
       inflater,
       container,
       internalProfileId,
       topicId,
       storyId,
+      rawUserAnswer,
+      arePreviousResponsesExpanded,
       explorationId
     )
   }
@@ -129,6 +144,18 @@ class StateFragment :
     stateFragmentPresenter.revealHint(hintIndex)
   }
 
+  override fun onSaveInstanceState(outState: Bundle) {
+    super.onSaveInstanceState(outState)
+    outState.putProto(
+      STATE_FRAGMENT_RAW_USER_ANSWER_KEY,
+      stateFragmentPresenter.getRawUserAnswer()
+    )
+    outState.putBoolean(
+      STATE_FRAGMENT_ARE_PREVIOUS_RESPONSES_HEADER_EXPANDED_KEY,
+      stateFragmentPresenter.getArePreviousResponsesExpanded()
+    )
+  }
+
   fun revealSolution() = stateFragmentPresenter.revealSolution()
 
   fun dismissConceptCard() = stateFragmentPresenter.dismissConceptCard()

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

@@ -24,6 +24,7 @@ import org.oppia.android.app.model.CheckpointState
 import org.oppia.android.app.model.EphemeralState
 import org.oppia.android.app.model.HelpIndex
 import org.oppia.android.app.model.ProfileId
+import org.oppia.android.app.model.RawUserAnswer
 import org.oppia.android.app.model.State
 import org.oppia.android.app.model.UserAnswer
 import org.oppia.android.app.player.audio.AudioButtonListener
@@ -47,6 +48,9 @@ import org.oppia.android.util.data.DataProvider
 import org.oppia.android.util.data.DataProviders.Companion.toLiveData
 import org.oppia.android.util.gcsresource.DefaultResourceBucketName
 import org.oppia.android.util.parser.html.ExplorationHtmlParserEntityType
+import org.oppia.android.util.platformparameter.EnableHintBulbAnimation
+import org.oppia.android.util.platformparameter.EnableInteractionConfigChangeStateRetention
+import org.oppia.android.util.platformparameter.PlatformParameterValue
 import org.oppia.android.util.system.OppiaClock
 import javax.inject.Inject
 
@@ -71,6 +75,10 @@ class StateFragmentPresenter @Inject constructor(
   private val storyProgressController: StoryProgressController,
   private val oppiaLogger: OppiaLogger,
   @DefaultResourceBucketName private val resourceBucketName: String,
+  @EnableInteractionConfigChangeStateRetention
+  private val isConfigChangeStateRetentionEnabled: PlatformParameterValue<Boolean>,
+  @EnableHintBulbAnimation
+  private val isHintBulbAnimationEnabled: PlatformParameterValue<Boolean>,
   private val assemblerBuilderFactory: StatePlayerRecyclerViewAssembler.Builder.Factory,
   private val splitScreenManager: SplitScreenManager,
   private val oppiaClock: OppiaClock
@@ -105,6 +113,8 @@ class StateFragmentPresenter @Inject constructor(
     internalProfileId: Int,
     topicId: String,
     storyId: String,
+    rawUserAnswer: RawUserAnswer,
+    arePreviousResponsesExpanded: Boolean,
     explorationId: String
   ): View? {
     profileId = ProfileId.newBuilder().setInternalId(internalProfileId).build()
@@ -118,7 +128,13 @@ class StateFragmentPresenter @Inject constructor(
       /* attachToRoot= */ false
     )
     recyclerViewAssembler = createRecyclerViewAssembler(
-      assemblerBuilderFactory.create(resourceBucketName, entityType, profileId),
+      assemblerBuilderFactory.create(
+        resourceBucketName,
+        entityType,
+        profileId,
+        rawUserAnswer,
+        arePreviousResponsesExpanded
+      ),
       binding.congratulationsTextView,
       binding.congratulationsTextConfettiView,
       binding.fullScreenConfettiView
@@ -164,7 +180,7 @@ class StateFragmentPresenter @Inject constructor(
 
   fun handleAnswerReadyForSubmission(answer: UserAnswer) {
     // An interaction has indicated that an answer is ready for submission.
-    handleSubmitAnswer(answer)
+    handleSubmitAnswer(answer, canSubmitAnswer = true)
   }
 
   fun onContinueButtonClicked() {
@@ -208,9 +224,7 @@ class StateFragmentPresenter @Inject constructor(
 
   fun handleKeyboardAction() {
     hideKeyboard()
-    if (viewModel.getCanSubmitAnswer().get() == true) {
-      handleSubmitAnswer(viewModel.getPendingAnswer(recyclerViewAssembler::getPendingAnswerHandler))
-    }
+    handleSubmitAnswer(viewModel.getPendingAnswer(recyclerViewAssembler::getPendingAnswerHandler))
   }
 
   fun onHintAvailable(helpIndex: HelpIndex, isCurrentStatePendingState: Boolean) {
@@ -261,6 +275,11 @@ class StateFragmentPresenter @Inject constructor(
     subscribeToHintSolution(explorationProgressController.submitSolutionIsRevealed())
   }
 
+  /** Returns whether previously submitted wrong answers are currently expanded. */
+  fun getArePreviousResponsesExpanded(): Boolean {
+    return recyclerViewAssembler.arePreviousResponsesExpanded
+  }
+
   private fun getStateViewModel(): StateViewModel {
     return viewModelProvider.getForFragment(fragment, StateViewModel::class.java)
   }
@@ -358,6 +377,9 @@ class StateFragmentPresenter @Inject constructor(
   private fun subscribeToAnswerOutcome(
     answerOutcomeResultLiveData: LiveData<AsyncResult<AnswerOutcome>>
   ) {
+    if (viewModel.getCanSubmitAnswer().get() == true) {
+      recyclerViewAssembler.resetRawUserAnswer()
+    }
     val answerOutcomeLiveData = getAnswerOutcome(answerOutcomeResultLiveData)
     answerOutcomeLiveData.observe(
       fragment,
@@ -401,8 +423,15 @@ class StateFragmentPresenter @Inject constructor(
     }
   }
 
-  private fun handleSubmitAnswer(answer: UserAnswer) {
-    subscribeToAnswerOutcome(explorationProgressController.submitAnswer(answer).toLiveData())
+  private fun handleSubmitAnswer(
+    answer: UserAnswer,
+    canSubmitAnswer: Boolean = viewModel.getCanSubmitAnswer().get() ?: false
+  ) {
+    // This check seems to avoid a crash on configuration change when attempting to resubmit answers
+    // after encountering a submit-time error, but it's also more correct to keep it.
+    if (canSubmitAnswer) {
+      subscribeToAnswerOutcome(explorationProgressController.submitAnswer(answer).toLiveData())
+    }
   }
 
   fun dismissConceptCard() {
@@ -451,6 +480,13 @@ class StateFragmentPresenter @Inject constructor(
   /** Returns the checkpoint state for the current exploration. */
   fun getExplorationCheckpointState() = explorationCheckpointState
 
+  /** Returns the [RawUserAnswer] representing the user's current pending answer. */
+  fun getRawUserAnswer(): RawUserAnswer {
+    return if (isConfigChangeStateRetentionEnabled.value) {
+      viewModel.getRawUserAnswer(recyclerViewAssembler::getPendingAnswerHandler)
+    } else RawUserAnswer.getDefaultInstance()
+  }
+
   private fun markExplorationCompleted() {
     storyProgressController.recordCompletedChapter(
       profileId,
@@ -494,6 +530,8 @@ class StateFragmentPresenter @Inject constructor(
 
   private fun setHintOpenedAndUnRevealed(isHintUnrevealed: Boolean) {
     viewModel.setHintOpenedAndUnRevealedVisibility(isHintUnrevealed)
+    if (!isHintBulbAnimationEnabled.value) return
+
     if (isHintUnrevealed) {
       val hintBulbAnimation = AnimationUtils.loadAnimation(
         context,