Fixes #4737: No meaningful label of the revision screen navigation ca…

…rds during talkback. (#5113)

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## Explanation
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Fixes #4737 

## Essential Checklist
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- [x] The PR title and explanation each start with "Fix #bugnum: " (If
this PR fixes part of an issue, prefix the title with "Fix part of
#bugnum: ...".)
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files have their rationale included in the PR explanation.
- [x] The PR follows the [style
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## For UI-specific PRs only
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- Add screenshots for portrait/landscape for both a tablet & phone of
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- Add a video showing the full UX flow with a screen reader enabled (see
[accessibility
guide](https://github.com/oppia/oppia-android/wiki/Accessibility-A11y-Guide))
- Add a screenshot demonstrating that you ran affected Espresso tests
locally & that they're passing


[talkback.webm](https://github.com/oppia/oppia-android/assets/92685493/c897e62f-3c8f-467f-88a8-e792f2974998)

---------

Co-authored-by: Adhiambo Peres <59600948+adhiamboperes@users.noreply.github.com>

app/BUILD.bazel

@@ -248,6 +248,7 @@ VIEW_MODELS_WITH_RESOURCE_IMPORTS = [
     "src/main/java/org/oppia/android/app/topic/lessons/ChapterSummaryViewModel.kt",
     "src/main/java/org/oppia/android/app/topic/lessons/StorySummaryViewModel.kt",
     "src/main/java/org/oppia/android/app/topic/questionplayer/QuestionPlayerViewModel.kt",
+    "src/main/java/org/oppia/android/app/topic/revisioncard/RevisionCardViewModel.kt",
     "src/main/java/org/oppia/android/app/utility/RatioExtensions.kt",
     "src/main/java/org/oppia/android/app/walkthrough/topiclist/topiclistviewmodel/WalkthroughTopicSummaryViewModel.kt",
 ]
@@ -365,7 +366,6 @@ VIEW_MODELS = [
     "src/main/java/org/oppia/android/app/topic/practice/TopicPracticeViewModel.kt",
     "src/main/java/org/oppia/android/app/topic/revision/revisionitemviewmodel/TopicRevisionItemViewModel.kt",
     "src/main/java/org/oppia/android/app/topic/revision/TopicRevisionViewModel.kt",
-    "src/main/java/org/oppia/android/app/topic/revisioncard/RevisionCardViewModel.kt",
     "src/main/java/org/oppia/android/app/walkthrough/end/WalkthroughFinalViewModel.kt",
     "src/main/java/org/oppia/android/app/walkthrough/topiclist/topiclistviewmodel/WalkthroughTopicHeaderViewModel.kt",
     "src/main/java/org/oppia/android/app/walkthrough/topiclist/WalkthroughTopicItemViewModel.kt",

app/src/main/java/org/oppia/android/app/topic/revisioncard/RevisionCardViewModel.kt

@@ -3,11 +3,13 @@ package org.oppia.android.app.topic.revisioncard
 import androidx.appcompat.app.AppCompatActivity
 import androidx.lifecycle.LiveData
 import androidx.lifecycle.Transformations
+import org.oppia.android.R
 import org.oppia.android.app.model.EphemeralRevisionCard
 import org.oppia.android.app.model.EphemeralSubtopic
 import org.oppia.android.app.model.EphemeralTopic
 import org.oppia.android.app.model.ProfileId
 import org.oppia.android.app.topic.RouteToRevisionCardListener
+import org.oppia.android.app.translation.AppLanguageResourceHandler
 import org.oppia.android.app.viewmodel.ObservableViewModel
 import org.oppia.android.domain.oppialogger.OppiaLogger
 import org.oppia.android.domain.topic.TopicController
@@ -36,6 +38,7 @@ class RevisionCardViewModel private constructor(
   val topicId: String,
   val subtopicId: Int,
   val profileId: ProfileId,
+  private val appLanguageResourceHandler: AppLanguageResourceHandler,
   val subtopicListSize: Int
 ) : ObservableViewModel() {
 
@@ -100,6 +103,21 @@ class RevisionCardViewModel private constructor(
     } ?: ""
   }
 
+  /** Returns the content description of the subtopic. */
+  fun computeContentDescriptionText(subtopicLiveData: LiveData<EphemeralSubtopic>): String {
+    return when (subtopicLiveData) {
+      previousSubtopicLiveData -> appLanguageResourceHandler.getStringInLocaleWithWrapping(
+        R.string.previous_subtopic_talkback_text,
+        computeTitleText(previousSubtopicLiveData.value)
+      )
+      nextSubtopicLiveData -> appLanguageResourceHandler.getStringInLocaleWithWrapping(
+        R.string.next_subtopic_talkback_text,
+        computeTitleText(nextSubtopicLiveData.value)
+      )
+      else -> ""
+    }
+  }
+
   private fun processPreviousSubtopicData(
     topicLiveData: AsyncResult<EphemeralTopic>
   ): EphemeralSubtopic {
@@ -157,6 +175,7 @@ class RevisionCardViewModel private constructor(
     private val topicController: TopicController,
     private val oppiaLogger: OppiaLogger,
     @TopicHtmlParserEntityType private val entityType: String,
+    private val appLanguageResourceHandler: AppLanguageResourceHandler,
     private val translationController: TranslationController
   ) {
     /** Returns a new [RevisionCardViewModel]. */
@@ -175,6 +194,7 @@ class RevisionCardViewModel private constructor(
         topicId,
         subtopicId,
         profileId,
+        appLanguageResourceHandler,
         subtopicListSize
       )
     }

app/src/main/res/layout-sw600dp/revision_card_fragment.xml

@@ -108,6 +108,7 @@
                 android:paddingEnd="@dimen/topic_revision_summary_view_subtopic_title_text_view_padding_end"
                 android:paddingBottom="16dp"
                 android:text="@{viewModel.computeTitleText(viewModel.previousSubtopicLiveData)}"
+                android:contentDescription="@{viewModel.computeContentDescriptionText(viewModel.previousSubtopicLiveData)}"
                 android:textColor="@color/component_color_shared_secondary_4_text_color"
                 android:textSize="14sp"
                 android:textStyle="bold"
@@ -166,6 +167,7 @@
                 android:paddingEnd="@dimen/topic_revision_summary_view_subtopic_title_text_view_padding_end"
                 android:paddingBottom="16dp"
                 android:text="@{viewModel.computeTitleText(viewModel.nextSubtopicLiveData)}"
+                android:contentDescription="@{viewModel.computeContentDescriptionText(viewModel.nextSubtopicLiveData)}"
                 android:textColor="@color/component_color_shared_secondary_4_text_color"
                 android:textSize="14sp"
                 android:textStyle="bold"

app/src/main/res/layout/revision_card_fragment.xml

@@ -106,6 +106,7 @@
               android:paddingEnd="@dimen/topic_revision_summary_view_subtopic_title_text_view_padding_end"
               android:paddingBottom="16dp"
               android:text="@{viewModel.computeTitleText(viewModel.previousSubtopicLiveData)}"
+              android:contentDescription="@{viewModel.computeContentDescriptionText(viewModel.previousSubtopicLiveData)}"
               android:textColor="@color/component_color_shared_secondary_4_text_color"
               android:textSize="14sp"
               android:textStyle="bold"
@@ -164,6 +165,7 @@
               android:paddingEnd="@dimen/topic_revision_summary_view_subtopic_title_text_view_padding_end"
               android:paddingBottom="16dp"
               android:text="@{viewModel.computeTitleText(viewModel.nextSubtopicLiveData)}"
+              android:contentDescription="@{viewModel.computeContentDescriptionText(viewModel.nextSubtopicLiveData)}"
               android:textColor="@color/component_color_shared_secondary_4_text_color"
               android:textSize="14sp"
               android:textStyle="bold"

app/src/main/res/values/strings.xml

@@ -623,4 +623,6 @@
   <string name="nps_passive_feedback_question">Thanks for responding! How can we provide a better experience?</string>
   <string name="nps_detractor_feedback_question">Help us improve your experience! Please share  the primary reason for your score:</string>
   <string name="nps_score_question">On a scale from 0–10, how likely are you to recommend %s to a friend or colleague?</string>
+  <string name="previous_subtopic_talkback_text">The previous subtopic is %s</string>
+  <string name="next_subtopic_talkback_text">The next subtopic is %s</string>
 </resources>

app/src/sharedTest/java/org/oppia/android/app/topic/revisioncard/RevisionCardFragmentTest.kt

@@ -21,6 +21,7 @@ import androidx.test.espresso.intent.Intents.intended
 import androidx.test.espresso.intent.matcher.IntentMatchers.hasComponent
 import androidx.test.espresso.intent.matcher.IntentMatchers.hasExtra
 import androidx.test.espresso.matcher.RootMatchers.isDialog
+import androidx.test.espresso.matcher.ViewMatchers
 import androidx.test.espresso.matcher.ViewMatchers.isDisplayed
 import androidx.test.espresso.matcher.ViewMatchers.isRoot
 import androidx.test.espresso.matcher.ViewMatchers.withId
@@ -183,6 +184,50 @@ class RevisionCardFragmentTest {
     Intents.release()
   }
 
+  @Test
+  fun testRevisionCard_previousSubtopicTitle_whatIsAFraction_hasCorrectContentDescription() {
+    launch<RevisionCardActivity>(
+      createRevisionCardActivityIntent(
+        context,
+        profileId.internalId,
+        FRACTIONS_TOPIC_ID,
+        subtopicId = 2,
+        FRACTIONS_SUBTOPIC_LIST_SIZE
+      )
+    ).use {
+      testCoroutineDispatchers.runCurrent()
+      onView(withId(R.id.prev_subtopic_title)).check(
+        matches(
+          ViewMatchers.withContentDescription(
+            "The previous subtopic is What is a Fraction?"
+          )
+        )
+      )
+    }
+  }
+
+  @Test
+  fun testRevisionCard_nextSubtopicTitle_mixedNumbers_hasCorrectContentDescription() {
+    launch<RevisionCardActivity>(
+      createRevisionCardActivityIntent(
+        context,
+        profileId.internalId,
+        FRACTIONS_TOPIC_ID,
+        subtopicId = 2,
+        FRACTIONS_SUBTOPIC_LIST_SIZE
+      )
+    ).use {
+      testCoroutineDispatchers.runCurrent()
+      onView(withId(R.id.next_subtopic_title)).check(
+        matches(
+          ViewMatchers.withContentDescription(
+            "The next subtopic is Mixed Numbers"
+          )
+        )
+      )
+    }
+  }
+
   @Test
   fun testRevisionCardTest_initialise_openBottomSheet_showsBottomSheet() {
     launch<ExplorationActivity>(