Merge branch 'develop' of github.com:oppia/oppia-android into new-onb…

…oarding-ui

app/BUILD.bazel

@@ -222,6 +222,7 @@ VIEW_MODELS_WITH_RESOURCE_IMPORTS = [
     "src/main/java/org/oppia/android/app/parser/StringToNumberParser.kt",
     "src/main/java/org/oppia/android/app/parser/StringToRatioParser.kt",
     "src/main/java/org/oppia/android/app/player/audio/AudioViewModel.kt",
+    "src/main/java/org/oppia/android/app/player/state/itemviewmodel/DragAndDropSortInteractionViewModel.kt",
     "src/main/java/org/oppia/android/app/player/state/itemviewmodel/DragDropInteractionContentViewModel.kt",
     "src/main/java/org/oppia/android/app/player/state/itemviewmodel/FractionInteractionViewModel.kt",
     "src/main/java/org/oppia/android/app/player/state/itemviewmodel/ImageRegionSelectionInteractionViewModel.kt",
@@ -321,7 +322,6 @@ VIEW_MODELS = [
     "src/main/java/org/oppia/android/app/player/state/itemviewmodel/ContentViewModel.kt",
     "src/main/java/org/oppia/android/app/player/state/itemviewmodel/ContinueInteractionViewModel.kt",
     "src/main/java/org/oppia/android/app/player/state/itemviewmodel/ContinueNavigationButtonViewModel.kt",
-    "src/main/java/org/oppia/android/app/player/state/itemviewmodel/DragAndDropSortInteractionViewModel.kt",
     "src/main/java/org/oppia/android/app/player/state/itemviewmodel/FeedbackViewModel.kt",
     "src/main/java/org/oppia/android/app/player/state/itemviewmodel/NextButtonViewModel.kt",
     "src/main/java/org/oppia/android/app/player/state/itemviewmodel/NumericInputViewModel.kt",

app/src/main/AndroidManifest.xml

@@ -215,6 +215,7 @@
     <activity android:name=".app.testing.ExplorationInjectionActivity" />
     <activity android:name=".app.testing.ExplorationTestActivity" />
     <activity android:name=".app.testing.FractionInputInteractionViewTestActivity" />
+    <activity android:name=".app.testing.TextInputInteractionViewTestActivity" />
     <activity
       android:name=".app.testing.TestFontScaleConfigurationUtilActivity"
       android:theme="@style/OppiaThemeWithoutActionBar" />
@@ -224,6 +225,7 @@
     <activity android:name=".app.testing.InputInteractionViewTestActivity" />
     <activity android:name=".app.testing.RatioInputInteractionViewTestActivity" />
     <activity android:name=".app.testing.ImageRegionSelectionTestActivity" />
+    <activity android:name=".app.testing.MathExpressionInteractionsViewTestActivity" />
     <activity android:name=".app.testing.ImageViewBindingAdaptersTestActivity" />
     <activity android:name=".app.testing.ListItemLeadingMarginSpanTestActivity" />
     <activity android:name=".app.testing.MarginBindingAdaptersTestActivity" />

app/src/main/java/org/oppia/android/app/activity/ActivityComponentImpl.kt

@@ -76,6 +76,7 @@ import org.oppia.android.app.testing.ImageViewBindingAdaptersTestActivity
 import org.oppia.android.app.testing.InputInteractionViewTestActivity
 import org.oppia.android.app.testing.ListItemLeadingMarginSpanTestActivity
 import org.oppia.android.app.testing.MarginBindingAdaptersTestActivity
+import org.oppia.android.app.testing.MathExpressionInteractionsViewTestActivity
 import org.oppia.android.app.testing.NavigationDrawerTestActivity
 import org.oppia.android.app.testing.PoliciesFragmentTestActivity
 import org.oppia.android.app.testing.ProfileChooserFragmentTestActivity
@@ -86,6 +87,7 @@ import org.oppia.android.app.testing.SpotlightFragmentTestActivity
 import org.oppia.android.app.testing.StateAssemblerMarginBindingAdaptersTestActivity
 import org.oppia.android.app.testing.StateAssemblerPaddingBindingAdaptersTestActivity
 import org.oppia.android.app.testing.TestFontScaleConfigurationUtilActivity
+import org.oppia.android.app.testing.TextInputInteractionViewTestActivity
 import org.oppia.android.app.testing.TextViewBindingAdaptersTestActivity
 import org.oppia.android.app.testing.TopicRevisionTestActivity
 import org.oppia.android.app.testing.TopicTestActivity
@@ -154,6 +156,8 @@ interface ActivityComponentImpl :
   fun inject(imageRegionSelectionTestActivity: ImageRegionSelectionTestActivity)
   fun inject(imageViewBindingAdaptersTestActivity: ImageViewBindingAdaptersTestActivity)
   fun inject(inputInteractionViewTestActivity: InputInteractionViewTestActivity)
+  fun inject(textInputInteractionViewTestActivity: TextInputInteractionViewTestActivity)
+  fun inject(mathExpressionInteractionsViewTestActivity: MathExpressionInteractionsViewTestActivity)
   fun inject(ratioInputInteractionViewTestActivity: RatioInputInteractionViewTestActivity)
   fun inject(licenseListActivity: LicenseListActivity)
   fun inject(licenseTextViewerActivity: LicenseTextViewerActivity)

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

@@ -1,8 +1,10 @@
 package org.oppia.android.app.player.state.itemviewmodel
 
+import androidx.annotation.StringRes
 import androidx.databinding.Observable
 import androidx.databinding.ObservableField
 import androidx.recyclerview.widget.RecyclerView
+import org.oppia.android.R
 import org.oppia.android.app.model.Interaction
 import org.oppia.android.app.model.InteractionObject
 import org.oppia.android.app.model.ListOfSetsOfHtmlStrings
@@ -13,6 +15,7 @@ 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.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
@@ -23,6 +26,18 @@ import org.oppia.android.app.translation.AppLanguageResourceHandler
 import org.oppia.android.domain.translation.TranslationController
 import javax.inject.Inject
 
+/** Represents the type of errors that can be thrown by drag and drop sort interaction. */
+enum class DragAndDropSortInteractionError(@StringRes private var error: Int?) {
+  VALID(error = null),
+  EMPTY_INPUT(error = R.string.drag_and_drop_interaction_empty_input);
+
+  /**
+   * Returns the string corresponding to this error's string resources, or null if there is none.
+   */
+  fun getErrorMessageFromStringRes(resourceHandler: AppLanguageResourceHandler): String? =
+    error?.let(resourceHandler::getStringInLocale)
+}
+
 /** [StateItemViewModel] for drag drop & sort choice list. */
 class DragAndDropSortInteractionViewModel private constructor(
   val entityId: String,
@@ -55,25 +70,34 @@ class DragAndDropSortInteractionViewModel private constructor(
       subtitledHtml.contentId to translatedHtml
     }
 
-  private val _choiceItems: MutableList<DragDropInteractionContentViewModel> =
+  private val _originalChoiceItems: MutableList<DragDropInteractionContentViewModel> =
     computeChoiceItems(contentIdHtmlMap, choiceSubtitledHtmls, this, resourceHandler)
 
+  private val _choiceItems = _originalChoiceItems.toMutableList()
   val choiceItems: List<DragDropInteractionContentViewModel> = _choiceItems
 
+  private var pendingAnswerError: String? = null
   private val isAnswerAvailable = ObservableField(false)
+  var errorMessage = ObservableField<String>("")
 
   init {
     val callback: Observable.OnPropertyChangedCallback =
       object : Observable.OnPropertyChangedCallback() {
         override fun onPropertyChanged(sender: Observable, propertyId: Int) {
           interactionAnswerErrorOrAvailabilityCheckReceiver.onPendingAnswerErrorOrAvailabilityCheck(
-            pendingAnswerError = null,
-            inputAnswerAvailable = true
+            pendingAnswerError,
+            inputAnswerAvailable = true // Allow submission without arranging or merging items.
           )
         }
       }
     isAnswerAvailable.addOnPropertyChangedCallback(callback)
-    isAnswerAvailable.set(true) // For drag drop submit button will be enabled by default.
+    errorMessage.addOnPropertyChangedCallback(callback)
+
+    // Initializing with default values so that submit button is enabled by default.
+    interactionAnswerErrorOrAvailabilityCheckReceiver.onPendingAnswerErrorOrAvailabilityCheck(
+      pendingAnswerError = null,
+      inputAnswerAvailable = true
+    )
   }
 
   override fun onItemDragged(
@@ -98,6 +122,7 @@ class DragAndDropSortInteractionViewModel private constructor(
     if (allowMultipleItemsInSamePosition) {
       (adapter as BindableAdapter<*>).setDataUnchecked(_choiceItems)
     }
+    checkPendingAnswerError(AnswerErrorCategory.REAL_TIME)
   }
 
   fun onItemMoved(
@@ -129,6 +154,20 @@ class DragAndDropSortInteractionViewModel private constructor(
       this@DragAndDropSortInteractionViewModel.writtenTranslationContext
   }.build()
 
+  /**
+   * It checks the pending error for the current drag and drop sort interaction, and correspondingly
+   * updates the error string based on the specified error category.
+   */
+  override fun checkPendingAnswerError(category: AnswerErrorCategory): String? {
+    pendingAnswerError = when (category) {
+      AnswerErrorCategory.REAL_TIME -> null
+      AnswerErrorCategory.SUBMIT_TIME ->
+        getSubmitTimeError().getErrorMessageFromStringRes(resourceHandler)
+    }
+    errorMessage.set(pendingAnswerError)
+    return pendingAnswerError
+  }
+
   /** 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()
@@ -190,6 +229,13 @@ class DragAndDropSortInteractionViewModel private constructor(
     (adapter as BindableAdapter<*>).setDataUnchecked(_choiceItems)
   }
 
+  private fun getSubmitTimeError(): DragAndDropSortInteractionError {
+    return if (_originalChoiceItems == _choiceItems)
+      DragAndDropSortInteractionError.EMPTY_INPUT
+    else
+      DragAndDropSortInteractionError.VALID
+  }
+
   /** Implementation of [StateItemViewModel.InteractionItemFactory] for this view model. */
   class FactoryImpl @Inject constructor(
     private val resourceHandler: AppLanguageResourceHandler,

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

@@ -105,12 +105,18 @@ class MathExpressionInteractionsViewModel private constructor(
         override fun onPropertyChanged(sender: Observable, propertyId: Int) {
           errorOrAvailabilityCheckReceiver.onPendingAnswerErrorOrAvailabilityCheck(
             pendingAnswerError,
-            answerText.isNotEmpty()
+            inputAnswerAvailable = true // Allow blank answer submission.
           )
         }
       }
     errorMessage.addOnPropertyChangedCallback(callback)
     isAnswerAvailable.addOnPropertyChangedCallback(callback)
+
+    // Initializing with default values so that submit button is enabled by default.
+    errorOrAvailabilityCheckReceiver.onPendingAnswerErrorOrAvailabilityCheck(
+      pendingAnswerError = null,
+      inputAnswerAvailable = true
+    )
   }
 
   override fun getPendingAnswer(): UserAnswer = UserAnswer.newBuilder().apply {
@@ -147,18 +153,16 @@ class MathExpressionInteractionsViewModel private constructor(
   }.build()
 
   override fun checkPendingAnswerError(category: AnswerErrorCategory): String? {
-    if (answerText.isNotEmpty()) {
-      pendingAnswerError = when (category) {
-        // There's no support for real-time errors.
-        AnswerErrorCategory.REAL_TIME -> null
-        AnswerErrorCategory.SUBMIT_TIME -> {
-          interactionType.computeSubmitTimeError(
-            answerText.toString(), allowedVariables, resourceHandler
-          )
-        }
+    pendingAnswerError = when (category) {
+      // There's no support for real-time errors.
+      AnswerErrorCategory.REAL_TIME -> null
+      AnswerErrorCategory.SUBMIT_TIME -> {
+        interactionType.computeSubmitTimeError(
+          answerText.toString(), allowedVariables, resourceHandler
+        )
       }
-      errorMessage.set(pendingAnswerError)
     }
+    errorMessage.set(pendingAnswerError)
     return pendingAnswerError
   }
 
@@ -290,7 +294,10 @@ class MathExpressionInteractionsViewModel private constructor(
   }
 
   private companion object {
-    private enum class InteractionType(
+    /**
+     * Enum class representing different types of interactions in a mathematical expression input field.
+     */
+    enum class InteractionType(
       val viewType: ViewType,
       @StringRes val defaultHintTextStringId: Int,
       val hasPlaceholder: Boolean,
@@ -420,6 +427,25 @@ class MathExpressionInteractionsViewModel private constructor(
         allowedVariables: List<String>,
         appLanguageResourceHandler: AppLanguageResourceHandler
       ): String? {
+        if (answerText.isBlank()) {
+          return when (this) {
+            NUMERIC_EXPRESSION -> {
+              appLanguageResourceHandler.getStringInLocale(
+                R.string.numeric_expression_error_empty_input
+              )
+            }
+            ALGEBRAIC_EXPRESSION -> {
+              appLanguageResourceHandler.getStringInLocale(
+                R.string.algebraic_expression_error_empty_input
+              )
+            }
+            MATH_EQUATION -> {
+              appLanguageResourceHandler.getStringInLocale(
+                R.string.math_equation_error_empty_input
+              )
+            }
+          }
+        }
         return when (val parseResult = parseAnswer(answerText, allowedVariables)) {
           is MathParsingResult.Failure -> when (val error = parseResult.error) {
             is DisabledVariablesInUseError -> {

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

@@ -2,13 +2,15 @@ package org.oppia.android.app.player.state.itemviewmodel
 
 import android.text.Editable
 import android.text.TextWatcher
+import androidx.annotation.StringRes
 import androidx.databinding.Observable
 import androidx.databinding.ObservableField
 import org.oppia.android.R
 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.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
@@ -28,20 +30,43 @@ class TextInputViewModel private constructor(
 ) : StateItemViewModel(ViewType.TEXT_INPUT_INTERACTION), InteractionAnswerHandler {
   var answerText: CharSequence = ""
   val hintText: CharSequence = deriveHintText(interaction)
+  private var pendingAnswerError: String? = null
 
   var isAnswerAvailable = ObservableField<Boolean>(false)
+  val errorMessage = ObservableField<String>("")
 
   init {
     val callback: Observable.OnPropertyChangedCallback =
       object : Observable.OnPropertyChangedCallback() {
         override fun onPropertyChanged(sender: Observable, propertyId: Int) {
           interactionAnswerErrorOrAvailabilityCheckReceiver.onPendingAnswerErrorOrAvailabilityCheck(
-            /* pendingAnswerError= */ null,
-            answerText.isNotEmpty()
+            pendingAnswerError = pendingAnswerError,
+            inputAnswerAvailable = true // Allow submit on empty answer.
           )
         }
       }
     isAnswerAvailable.addOnPropertyChangedCallback(callback)
+    errorMessage.addOnPropertyChangedCallback(callback)
+
+    // Initializing with default values so that submit button is enabled by default.
+    interactionAnswerErrorOrAvailabilityCheckReceiver.onPendingAnswerErrorOrAvailabilityCheck(
+      pendingAnswerError = null,
+      inputAnswerAvailable = true
+    )
+  }
+
+  override fun checkPendingAnswerError(category: AnswerErrorCategory): String? {
+    return when (category) {
+      AnswerErrorCategory.REAL_TIME -> null
+      AnswerErrorCategory.SUBMIT_TIME -> {
+        TextParsingUiError.createForText(
+          answerText.toString()
+        ).createForText(resourceHandler)
+      }
+    }.also {
+      pendingAnswerError = it
+      errorMessage.set(it)
+    }
   }
 
   fun getAnswerTextWatcher(): TextWatcher {
@@ -55,6 +80,7 @@ class TextInputViewModel private constructor(
         if (isAnswerTextAvailable != isAnswerAvailable.get()) {
           isAnswerAvailable.set(isAnswerTextAvailable)
         }
+        checkPendingAnswerError(AnswerErrorCategory.REAL_TIME)
       }
 
       override fun afterTextChanged(s: Editable) {
@@ -121,4 +147,22 @@ class TextInputViewModel private constructor(
       )
     }
   }
+
+  private enum class TextParsingUiError(@StringRes private var error: Int?) {
+    /** Corresponds to non empty input. */
+    VALID(error = null),
+
+    /** Corresponds to empty input. */
+    EMPTY_INPUT(error = R.string.text_error_empty_input);
+
+    /** Returns the string corresponding to this error's string resources, or null if there is none. */
+    fun createForText(resourceHandler: AppLanguageResourceHandler): String? =
+      error?.let(resourceHandler::getStringInLocale)
+
+    companion object {
+      /** Returns the [TextParsingUiError] corresponding to the input. */
+      fun createForText(text: String): TextParsingUiError =
+        if (text.isEmpty()) EMPTY_INPUT else VALID
+    }
+  }
 }