Fix part of #4470, Fix #4471, Fix 4474: Handle configuration change using onSavedInstance.

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

@@ -10,6 +10,7 @@ import org.oppia.android.app.fragment.InjectableFragment
 import org.oppia.android.app.model.HelpIndex
 import org.oppia.android.app.model.StateFragmentArguments
 import org.oppia.android.app.model.UserAnswer
+import org.oppia.android.app.model.UserAnswerState
 import org.oppia.android.app.player.state.answerhandling.InteractionAnswerErrorOrAvailabilityCheckReceiver
 import org.oppia.android.app.player.state.answerhandling.InteractionAnswerHandler
 import org.oppia.android.app.player.state.answerhandling.InteractionAnswerReceiver
@@ -42,6 +43,9 @@ class StateFragment :
     /** Arguments key for StateFragment. */
     const val STATE_FRAGMENT_ARGUMENTS_KEY = "StateFragment.arguments"
 
+    /** Arguments key for StateFragment saved state. */
+    const val STATE_FRAGMENT_STATE_KEY = "StateFragment.state"
+
     /**
      * Creates a new instance of a StateFragment.
      * @param internalProfileId used by StateFragment to mark progress.
@@ -86,6 +90,12 @@ class StateFragment :
   ): View? {
     val args =
       arguments?.getProto(STATE_FRAGMENT_ARGUMENTS_KEY, StateFragmentArguments.getDefaultInstance())
+
+    val userAnswerState = savedInstanceState?.getProto(
+      STATE_FRAGMENT_STATE_KEY,
+      UserAnswerState.getDefaultInstance()
+    ) ?: UserAnswerState.getDefaultInstance()
+
     val internalProfileId = args?.internalProfileId ?: -1
     val topicId = args?.topicId!!
     val storyId = args.storyId!!
@@ -97,7 +107,8 @@ class StateFragment :
       internalProfileId,
       topicId,
       storyId,
-      explorationId
+      explorationId,
+      userAnswerState
     )
   }
 
@@ -154,4 +165,12 @@ class StateFragment :
   fun dismissConceptCard() = stateFragmentPresenter.dismissConceptCard()
 
   fun getExplorationCheckpointState() = stateFragmentPresenter.getExplorationCheckpointState()
+
+  override fun onSaveInstanceState(outState: Bundle) {
+    super.onSaveInstanceState(outState)
+    outState.putProto(
+      STATE_FRAGMENT_STATE_KEY,
+      stateFragmentPresenter.getUserAnswerState()
+    )
+  }
 }

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

@@ -27,6 +27,7 @@ import org.oppia.android.app.model.ProfileId
 import org.oppia.android.app.model.State
 import org.oppia.android.app.model.SurveyQuestionName
 import org.oppia.android.app.model.UserAnswer
+import org.oppia.android.app.model.UserAnswerState
 import org.oppia.android.app.player.audio.AudioButtonListener
 import org.oppia.android.app.player.audio.AudioFragment
 import org.oppia.android.app.player.audio.AudioUiManager
@@ -111,7 +112,8 @@ class StateFragmentPresenter @Inject constructor(
     internalProfileId: Int,
     topicId: String,
     storyId: String,
-    explorationId: String
+    explorationId: String,
+    userAnswerState: UserAnswerState
   ): View? {
     profileId = ProfileId.newBuilder().setInternalId(internalProfileId).build()
     this.topicId = topicId
@@ -125,7 +127,7 @@ class StateFragmentPresenter @Inject constructor(
       /* attachToRoot= */ false
     )
     recyclerViewAssembler = createRecyclerViewAssembler(
-      assemblerBuilderFactory.create(resourceBucketName, entityType, profileId),
+      assemblerBuilderFactory.create(resourceBucketName, entityType, profileId, userAnswerState),
       binding.congratulationsTextView,
       binding.congratulationsTextConfettiView,
       binding.fullScreenConfettiView
@@ -373,6 +375,7 @@ class StateFragmentPresenter @Inject constructor(
   private fun subscribeToAnswerOutcome(
     answerOutcomeResultLiveData: LiveData<AsyncResult<AnswerOutcome>>
   ) {
+    recyclerViewAssembler.resetUserAnswerState()
     val answerOutcomeLiveData = getAnswerOutcome(answerOutcomeResultLiveData)
     answerOutcomeLiveData.observe(
       fragment,
@@ -393,6 +396,11 @@ class StateFragmentPresenter @Inject constructor(
     )
   }
 
+  /** Returns the [UserAnswerState] representing the user's current pending answer. */
+  fun getUserAnswerState(): UserAnswerState {
+    return stateViewModel.getUserAnswerState(recyclerViewAssembler::getPendingAnswerHandler)
+  }
+
   /** Helper for subscribeToAnswerOutcome. */
   private fun getAnswerOutcome(
     answerOutcome: LiveData<AsyncResult<AnswerOutcome>>

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

@@ -28,6 +28,7 @@ import org.oppia.android.app.model.ProfileId
 import org.oppia.android.app.model.StringList
 import org.oppia.android.app.model.SubtitledHtml
 import org.oppia.android.app.model.UserAnswer
+import org.oppia.android.app.model.UserAnswerState
 import org.oppia.android.app.model.WrittenTranslationContext
 import org.oppia.android.app.player.audio.AudioUiManager
 import org.oppia.android.app.player.state.StatePlayerRecyclerViewAssembler.Builder.Factory
@@ -143,7 +144,8 @@ class StatePlayerRecyclerViewAssembler private constructor(
   backgroundCoroutineDispatcher: CoroutineDispatcher,
   private val hasConversationView: Boolean,
   private val resourceHandler: AppLanguageResourceHandler,
-  private val translationController: TranslationController
+  private val translationController: TranslationController,
+  private var userAnswerState: UserAnswerState
 ) : HtmlParser.CustomOppiaTagActionListener {
   /**
    * A list of view models corresponding to past view models that are hidden by default. These are
@@ -323,10 +325,16 @@ class StatePlayerRecyclerViewAssembler private constructor(
       hasPreviousButton,
       isSplitView.get()!!,
       writtenTranslationContext,
-      timeToStartNoticeAnimationMs
+      timeToStartNoticeAnimationMs,
+      userAnswerState
     )
   }
 
+  /** Reset userAnswerState once the user submits an answer. */
+  fun resetUserAnswerState() {
+    userAnswerState = UserAnswerState.getDefaultInstance()
+  }
+
   private fun addContentItem(
     pendingItemList: MutableList<StateItemViewModel>,
     ephemeralState: EphemeralState,
@@ -904,7 +912,8 @@ class StatePlayerRecyclerViewAssembler private constructor(
     private val resourceHandler: AppLanguageResourceHandler,
     private val translationController: TranslationController,
     private val multiTypeBuilderFactory: BindableAdapter.MultiTypeBuilder.Factory,
-    private val singleTypeBuilderFactory: BindableAdapter.SingleTypeBuilder.Factory
+    private val singleTypeBuilderFactory: BindableAdapter.SingleTypeBuilder.Factory,
+    private val userAnswerState: UserAnswerState
   ) {
 
     private val adapterBuilder: BindableAdapter.MultiTypeBuilder<StateItemViewModel,
@@ -1390,7 +1399,8 @@ class StatePlayerRecyclerViewAssembler private constructor(
         backgroundCoroutineDispatcher,
         hasConversationView,
         resourceHandler,
-        translationController
+        translationController,
+        userAnswerState
       )
       if (playerFeatureSet.conceptCardSupport) {
         customTagListener.proxyListener = assembler
@@ -1416,7 +1426,12 @@ class StatePlayerRecyclerViewAssembler private constructor(
        * Returns a new [Builder] for the specified GCS resource bucket information for loading
        * assets, and the current logged in [ProfileId].
        */
-      fun create(resourceBucketName: String, entityType: String, profileId: ProfileId): Builder {
+      fun create(
+        resourceBucketName: String,
+        entityType: String,
+        profileId: ProfileId,
+        userAnswerState: UserAnswerState
+      ): Builder {
         return Builder(
           accessibilityService,
           htmlParserFactory,
@@ -1430,7 +1445,8 @@ class StatePlayerRecyclerViewAssembler private constructor(
           resourceHandler,
           translationController,
           multiAdapterBuilderFactory,
-          singleAdapterFactory
+          singleAdapterFactory,
+          userAnswerState
         )
       }
     }

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

@@ -8,13 +8,14 @@ import androidx.lifecycle.Observer
 import androidx.lifecycle.Transformations
 import androidx.lifecycle.ViewModel
 import org.oppia.android.app.fragment.FragmentScope
+import org.oppia.android.app.model.AnswerErrorCategory
 import org.oppia.android.app.model.EphemeralState
 import org.oppia.android.app.model.OppiaLanguage
 import org.oppia.android.app.model.Profile
 import org.oppia.android.app.model.ProfileId
 import org.oppia.android.app.model.UserAnswer
+import org.oppia.android.app.model.UserAnswerState
 import org.oppia.android.app.model.WrittenTranslationLanguageSelection
-import org.oppia.android.app.player.state.answerhandling.AnswerErrorCategory
 import org.oppia.android.app.player.state.answerhandling.InteractionAnswerHandler
 import org.oppia.android.app.player.state.itemviewmodel.StateItemViewModel
 import org.oppia.android.app.viewmodel.ObservableArrayList
@@ -150,6 +151,13 @@ class StateViewModel @Inject constructor(
     )
   }
 
+  fun getUserAnswerState(
+    retrieveAnswerHandler: (List<StateItemViewModel>) -> InteractionAnswerHandler?
+  ): UserAnswerState {
+    return retrieveAnswerHandler(getAnswerItemList())?.getUserAnswerState()
+      ?: UserAnswerState.getDefaultInstance()
+  }
+
   private fun getPendingAnswerWithoutError(
     answerHandler: InteractionAnswerHandler?
   ): UserAnswer? {

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

@@ -1,6 +1,8 @@
 package org.oppia.android.app.player.state.answerhandling
 
+import org.oppia.android.app.model.AnswerErrorCategory
 import org.oppia.android.app.model.UserAnswer
+import org.oppia.android.app.model.UserAnswerState
 
 /**
  * A handler for interaction answers. Handlers can either require an additional user action before the answer can be
@@ -26,6 +28,11 @@ interface InteractionAnswerHandler {
   fun getPendingAnswer(): UserAnswer? {
     return null
   }
+
+  /** Returns the current pending answer. */
+  fun getUserAnswerState(): UserAnswerState {
+    return UserAnswerState.getDefaultInstance()
+  }
 }
 
 /**
@@ -35,11 +42,3 @@ interface InteractionAnswerHandler {
 interface InteractionAnswerReceiver {
   fun onAnswerReadyForSubmission(answer: UserAnswer)
 }
-
-/** Categories of errors that can be inferred from a pending answer. */
-enum class AnswerErrorCategory {
-  /** Corresponds to errors that may be found while the user is trying to input an answer. */
-  REAL_TIME,
-  /** Corresponds to errors that may be found only when a user tries to submit an answer. */
-  SUBMIT_TIME
-}

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

@@ -4,6 +4,7 @@ import androidx.fragment.app.Fragment
 import org.oppia.android.app.model.Interaction
 import org.oppia.android.app.model.InteractionObject
 import org.oppia.android.app.model.UserAnswer
+import org.oppia.android.app.model.UserAnswerState
 import org.oppia.android.app.model.WrittenTranslationContext
 import org.oppia.android.app.player.state.answerhandling.InteractionAnswerErrorOrAvailabilityCheckReceiver
 import org.oppia.android.app.player.state.answerhandling.InteractionAnswerHandler
@@ -57,7 +58,8 @@ class ContinueInteractionViewModel private constructor(
       hasPreviousButton: Boolean,
       isSplitView: Boolean,
       writtenTranslationContext: WrittenTranslationContext,
-      timeToStartNoticeAnimationMs: Long?
+      timeToStartNoticeAnimationMs: Long?,
+      userAnswerState: UserAnswerState
     ): StateItemViewModel {
       return ContinueInteractionViewModel(
         interactionAnswerReceiver,

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

@@ -5,6 +5,7 @@ import androidx.databinding.Observable
 import androidx.databinding.ObservableField
 import androidx.recyclerview.widget.RecyclerView
 import org.oppia.android.R
+import org.oppia.android.app.model.AnswerErrorCategory
 import org.oppia.android.app.model.Interaction
 import org.oppia.android.app.model.InteractionObject
 import org.oppia.android.app.model.ListOfSetsOfHtmlStrings
@@ -14,8 +15,8 @@ import org.oppia.android.app.model.StringList
 import org.oppia.android.app.model.SubtitledHtml
 import org.oppia.android.app.model.TranslatableHtmlContentId
 import org.oppia.android.app.model.UserAnswer
+import org.oppia.android.app.model.UserAnswerState
 import org.oppia.android.app.model.WrittenTranslationContext
-import org.oppia.android.app.player.state.answerhandling.AnswerErrorCategory
 import org.oppia.android.app.player.state.answerhandling.InteractionAnswerErrorOrAvailabilityCheckReceiver
 import org.oppia.android.app.player.state.answerhandling.InteractionAnswerHandler
 import org.oppia.android.app.player.state.answerhandling.InteractionAnswerReceiver
@@ -163,6 +164,7 @@ class DragAndDropSortInteractionViewModel private constructor(
       AnswerErrorCategory.REAL_TIME -> null
       AnswerErrorCategory.SUBMIT_TIME ->
         getSubmitTimeError().getErrorMessageFromStringRes(resourceHandler)
+      else -> null
     }
     errorMessage.set(pendingAnswerError)
     return pendingAnswerError
@@ -250,7 +252,8 @@ class DragAndDropSortInteractionViewModel private constructor(
       hasPreviousButton: Boolean,
       isSplitView: Boolean,
       writtenTranslationContext: WrittenTranslationContext,
-      timeToStartNoticeAnimationMs: Long?
+      timeToStartNoticeAnimationMs: Long?,
+      userAnswerState: UserAnswerState
     ): StateItemViewModel {
       return DragAndDropSortInteractionViewModel(
         entityId,

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

@@ -5,12 +5,13 @@ import android.text.TextWatcher
 import androidx.databinding.Observable
 import androidx.databinding.ObservableField
 import org.oppia.android.R
+import org.oppia.android.app.model.AnswerErrorCategory
 import org.oppia.android.app.model.Interaction
 import org.oppia.android.app.model.InteractionObject
 import org.oppia.android.app.model.UserAnswer
+import org.oppia.android.app.model.UserAnswerState
 import org.oppia.android.app.model.WrittenTranslationContext
 import org.oppia.android.app.parser.FractionParsingUiError
-import org.oppia.android.app.player.state.answerhandling.AnswerErrorCategory
 import org.oppia.android.app.player.state.answerhandling.InteractionAnswerErrorOrAvailabilityCheckReceiver
 import org.oppia.android.app.player.state.answerhandling.InteractionAnswerHandler
 import org.oppia.android.app.player.state.answerhandling.InteractionAnswerReceiver
@@ -27,10 +28,12 @@ class FractionInteractionViewModel private constructor(
   private val errorOrAvailabilityCheckReceiver: InteractionAnswerErrorOrAvailabilityCheckReceiver,
   private val writtenTranslationContext: WrittenTranslationContext,
   private val resourceHandler: AppLanguageResourceHandler,
-  private val translationController: TranslationController
+  private val translationController: TranslationController,
+  userAnswerState: UserAnswerState
 ) : StateItemViewModel(ViewType.FRACTION_INPUT_INTERACTION), InteractionAnswerHandler {
   private var pendingAnswerError: String? = null
-  var answerText: CharSequence = ""
+  var answerText: CharSequence = userAnswerState.textInputAnswer
+  private var answerErrorCetegory: AnswerErrorCategory = AnswerErrorCategory.NO_ERROR
   var isAnswerAvailable = ObservableField<Boolean>(false)
   var errorMessage = ObservableField<String>("")
 
@@ -54,6 +57,7 @@ class FractionInteractionViewModel private constructor(
       /* pendingAnswerError= */null,
       /* inputAnswerAvailable= */true
     )
+    checkPendingAnswerError(userAnswerState.answerErrorCategory)
   }
 
   override fun getPendingAnswer(): UserAnswer = UserAnswer.newBuilder().apply {
@@ -69,6 +73,7 @@ class FractionInteractionViewModel private constructor(
 
   /** 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? {
+    answerErrorCetegory = category
     when (category) {
       AnswerErrorCategory.REAL_TIME -> {
         if (answerText.isNotEmpty()) {
@@ -86,6 +91,7 @@ class FractionInteractionViewModel private constructor(
             fractionParser.getSubmitTimeError(answerText.toString())
           ).getErrorMessageFromStringRes(resourceHandler)
       }
+      else -> {}
     }
     errorMessage.set(pendingAnswerError)
     return pendingAnswerError
@@ -110,6 +116,13 @@ class FractionInteractionViewModel private constructor(
     }
   }
 
+  override fun getUserAnswerState(): UserAnswerState {
+    return UserAnswerState.newBuilder().apply {
+      this.textInputAnswer = answerText.toString()
+      this.answerErrorCategory = answerErrorCetegory
+    }.build()
+  }
+
   private fun deriveHintText(interaction: Interaction): CharSequence {
     // The subtitled unicode can apparently exist in the structure in two different formats.
     val placeholderUnicodeOption1 =
@@ -149,7 +162,8 @@ class FractionInteractionViewModel private constructor(
       hasPreviousButton: Boolean,
       isSplitView: Boolean,
       writtenTranslationContext: WrittenTranslationContext,
-      timeToStartNoticeAnimationMs: Long?
+      timeToStartNoticeAnimationMs: Long?,
+      userAnswerState: UserAnswerState
     ): StateItemViewModel {
       return FractionInteractionViewModel(
         interaction,
@@ -158,7 +172,8 @@ class FractionInteractionViewModel private constructor(
         answerErrorReceiver,
         writtenTranslationContext,
         resourceHandler,
-        translationController
+        translationController,
+        userAnswerState
       )
     }
   }