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

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

@@ -375,9 +375,7 @@ class StateFragmentPresenter @Inject constructor(
   private fun subscribeToAnswerOutcome(
     answerOutcomeResultLiveData: LiveData<AsyncResult<AnswerOutcome>>
   ) {
-    if (stateViewModel.getCanSubmitAnswer().get() == true) {
-      recyclerViewAssembler.resetUserAnswerState()
-    }
+    recyclerViewAssembler.resetUserAnswerState()
     val answerOutcomeLiveData = getAnswerOutcome(answerOutcomeResultLiveData)
     answerOutcomeLiveData.observe(
       fragment,

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

@@ -1430,7 +1430,7 @@ class StatePlayerRecyclerViewAssembler private constructor(
         resourceBucketName: String,
         entityType: String,
         profileId: ProfileId,
-        userAnswerState: UserAnswerState = UserAnswerState.getDefaultInstance()
+        userAnswerState: UserAnswerState
       ): Builder {
         return Builder(
           accessibilityService,

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

@@ -32,8 +32,8 @@ class FractionInteractionViewModel private constructor(
   userAnswerState: UserAnswerState
 ) : StateItemViewModel(ViewType.FRACTION_INPUT_INTERACTION), InteractionAnswerHandler {
   private var pendingAnswerError: String? = null
-  var answerText: CharSequence = userAnswerState.textualAnswer
-  private var answerErrorCetegory: AnswerErrorCategory = AnswerErrorCategory.NO_ERROR_UNSPECIFIED
+  var answerText: CharSequence = userAnswerState.textInputAnswer
+  private var answerErrorCetegory: AnswerErrorCategory = AnswerErrorCategory.NO_ERROR
   var isAnswerAvailable = ObservableField<Boolean>(false)
   var errorMessage = ObservableField<String>("")
 
@@ -118,7 +118,7 @@ class FractionInteractionViewModel private constructor(
 
   override fun getUserAnswerState(): UserAnswerState {
     return UserAnswerState.newBuilder().apply {
-      this.textualAnswer = answerText.toString()
+      this.textInputAnswer = answerText.toString()
       this.answerErrorCategory = answerErrorCetegory
     }.build()
   }

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

@@ -74,15 +74,15 @@ class MathExpressionInteractionsViewModel private constructor(
    * Defines the current answer text being entered by the learner. This is expected to be directly
    * bound to the corresponding edit text.
    */
-  var answerText: CharSequence = userAnswerState.textualAnswer
+  var answerText: CharSequence = userAnswerState.textInputAnswer
     // The value of ths field is set from the Binding and from the TextWatcher. Any
     // programmatic modification needs to be done here, so that the Binding and the TextWatcher
     // do not step on each other.
     set(value) {
       field = value.toString().trim()
     }
 
-  private var answerErrorCetegory: AnswerErrorCategory = AnswerErrorCategory.NO_ERROR_UNSPECIFIED
+  private var answerErrorCetegory: AnswerErrorCategory = AnswerErrorCategory.NO_ERROR
 
   /**
    * Defines whether an answer is currently available to parse. This is expected to be directly
@@ -126,7 +126,7 @@ class MathExpressionInteractionsViewModel private constructor(
 
   override fun getUserAnswerState(): UserAnswerState {
     return UserAnswerState.newBuilder().apply {
-      this.textualAnswer = answerText.toString()
+      this.textInputAnswer = answerText.toString()
       this.answerErrorCategory = answerErrorCetegory
     }.build()
   }

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

@@ -26,8 +26,8 @@ class NumericInputViewModel private constructor(
   private val resourceHandler: AppLanguageResourceHandler,
   userAnswerState: UserAnswerState
 ) : StateItemViewModel(ViewType.NUMERIC_INPUT_INTERACTION), InteractionAnswerHandler {
-  var answerText: CharSequence = userAnswerState.textualAnswer
-  private var answerErrorCetegory: AnswerErrorCategory = AnswerErrorCategory.NO_ERROR_UNSPECIFIED
+  var answerText: CharSequence = userAnswerState.textInputAnswer
+  private var answerErrorCetegory: AnswerErrorCategory = AnswerErrorCategory.NO_ERROR
   private var pendingAnswerError: String? = null
   val errorMessage = ObservableField<String>("")
   var isAnswerAvailable = ObservableField<Boolean>(false)
@@ -77,7 +77,7 @@ class NumericInputViewModel private constructor(
 
   override fun getUserAnswerState(): UserAnswerState {
     return UserAnswerState.newBuilder().apply {
-      this.textualAnswer = answerText.toString()
+      this.textInputAnswer = answerText.toString()
       this.answerErrorCategory = answerErrorCetegory
     }.build()
   }

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

@@ -33,8 +33,8 @@ class RatioExpressionInputInteractionViewModel private constructor(
   userAnswerState: UserAnswerState
 ) : StateItemViewModel(ViewType.RATIO_EXPRESSION_INPUT_INTERACTION), InteractionAnswerHandler {
   private var pendingAnswerError: String? = null
-  var answerText: CharSequence = userAnswerState.textualAnswer
-  private var answerErrorCetegory: AnswerErrorCategory = AnswerErrorCategory.NO_ERROR_UNSPECIFIED
+  var answerText: CharSequence = userAnswerState.textInputAnswer
+  private var answerErrorCetegory: AnswerErrorCategory = AnswerErrorCategory.NO_ERROR
   var isAnswerAvailable = ObservableField<Boolean>(false)
   var errorMessage = ObservableField<String>("")
 
@@ -102,7 +102,7 @@ class RatioExpressionInputInteractionViewModel private constructor(
 
   override fun getUserAnswerState(): UserAnswerState {
     return UserAnswerState.newBuilder().apply {
-      this.textualAnswer = answerText.toString()
+      this.textInputAnswer = answerText.toString()
       this.answerErrorCategory = answerErrorCetegory
     }.build()
   }

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

@@ -64,7 +64,7 @@ class SelectionInteractionViewModel private constructor(
       ?: listOf()
   }
 
-  private var answerErrorCetegory: AnswerErrorCategory = AnswerErrorCategory.NO_ERROR_UNSPECIFIED
+  private var answerErrorCetegory: AnswerErrorCategory = AnswerErrorCategory.NO_ERROR
 
   private val minAllowableSelectionCount: Int by lazy {
     interaction.customizationArgsMap["minAllowableSelectionCount"]?.signedInt ?: 1

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

@@ -30,8 +30,8 @@ class TextInputViewModel private constructor(
   private val translationController: TranslationController,
   userAnswerState: UserAnswerState
 ) : StateItemViewModel(ViewType.TEXT_INPUT_INTERACTION), InteractionAnswerHandler {
-  var answerText: CharSequence = userAnswerState.textualAnswer
-  private var answerErrorCetegory: AnswerErrorCategory = AnswerErrorCategory.NO_ERROR_UNSPECIFIED
+  var answerText: CharSequence = userAnswerState.textInputAnswer
+  private var answerErrorCetegory: AnswerErrorCategory = AnswerErrorCategory.NO_ERROR
   val hintText: CharSequence = deriveHintText(interaction)
   private var pendingAnswerError: String? = null
 
@@ -107,7 +107,7 @@ class TextInputViewModel private constructor(
 
   override fun getUserAnswerState(): UserAnswerState {
     return UserAnswerState.newBuilder().apply {
-      this.textualAnswer = answerText.toString()
+      this.textInputAnswer = answerText.toString()
       this.answerErrorCategory = answerErrorCetegory
     }.build()
   }

model/src/main/proto/exploration.proto

@@ -421,31 +421,37 @@ enum CheckpointState {
   CHECKPOINT_UNSAVED = 3;
 }
 
-// Corresponds to a item selection answer that user has selected.
+// Represents the state of item selection answers that the user has selected.
 message ItemSelectionAnswerState {
+  // List of selected item indexes
   repeated int32 selected_indexes = 1;
 }
 
-// Corresponds to a raw representation of the current answer entered by the user
-// which is used to retain state on configuration changes
+// Represents the user's answer state, retaining state across configuration changes.
 message UserAnswerState {
+  // Represents the last error state.
   AnswerErrorCategory answer_error_category = 1;
-  oneof answer_input_type{
-    ItemSelectionAnswerState item_selection = 2;
 
-    // A raw answer entered by user in a text-based interactions.
-    string textual_answer = 3;
+  // Type of answer input:
+  oneof answer_input_type {
+    // User's selection for selection input interactions.
+    ItemSelectionAnswerState item_selection = 2;
+    // Raw answer entered by the user in text-based interactions.
+    string text_input_answer = 3;
   }
 }
 
 // Represents categories of errors that can be inferred from a pending answer.
 enum AnswerErrorCategory {
+  // The error is unknown or not specified.
+  ERROR_UNSPECIFIED = 0;
+
   // Corresponds to the pending answer having no error.
-  NO_ERROR_UNSPECIFIED = 0;
+  NO_ERROR = 1;
 
   // Corresponds to errors that may be found while the user is trying to input an answer.
-  REAL_TIME = 1;
+  REAL_TIME = 2;
 
   // Corresponds to errors that may be found only when a user tries to submit an answer.
-  SUBMIT_TIME = 2;
+  SUBMIT_TIME = 3;
 }