fix #19481: stop audio on previewer navigation

AnkiDroid/src/main/java/com/ichi2/anki/previewer/CardViewerViewModel.kt

@@ -56,13 +56,16 @@ abstract class CardViewerViewModel(
 
     val showingAnswer = savedStateHandle.getMutableStateFlow(KEY_SHOWING_ANSWER, false)
 
-    protected val cardMediaPlayer =
+    protected abstract val cardMediaPlayer: CardMediaPlayer
+
+    protected fun createCardMediaPlayer(): CardMediaPlayer =
         CardMediaPlayer(
             javascriptEvaluator = { launchCatchingIO { eval.emit(it) } },
             mediaErrorListener = mediaErrorHandler,
         ).also {
             addCloseable(it)
         }
+
     abstract var currentCard: Deferred<Card>
 
     abstract val server: AnkiServer

AnkiDroid/src/main/java/com/ichi2/anki/previewer/PreviewerViewModel.kt

@@ -23,6 +23,7 @@ import com.ichi2.anki.CollectionManager.withCol
 import com.ichi2.anki.Flag
 import com.ichi2.anki.asyncIO
 import com.ichi2.anki.browser.IdsFile
+import com.ichi2.anki.cardviewer.CardMediaPlayer
 import com.ichi2.anki.cardviewer.SingleCardSide
 import com.ichi2.anki.common.annotations.NeedsTest
 import com.ichi2.anki.launchCatchingIO
@@ -43,12 +44,14 @@ import kotlinx.coroutines.flow.MutableStateFlow
 import kotlinx.coroutines.flow.collectLatest
 import kotlinx.coroutines.flow.combine
 import kotlinx.coroutines.flow.update
+import kotlinx.coroutines.launch
 import timber.log.Timber
 
-class PreviewerViewModel(
+open class PreviewerViewModel(
     savedStateHandle: SavedStateHandle,
 ) : CardViewerViewModel(savedStateHandle),
     ChangeManager.Subscriber {
+    override val cardMediaPlayer by lazy { createCardMediaPlayer() }
     val currentIndex =
         savedStateHandle.getMutableStateFlow(
             KEY_CURRENT_INDEX,
@@ -246,6 +249,16 @@ class PreviewerViewModel(
             TypeAnswer.removeTags(text)
         }
 
+    override suspend fun showQuestion() {
+        cardMediaPlayer.stop()
+        super.showQuestion()
+    }
+
+    override suspend fun showAnswer() {
+        cardMediaPlayer.stop()
+        super.showAnswer()
+    }
+
     override fun opExecuted(
         changes: OpChanges,
         handler: Any?,

AnkiDroid/src/main/java/com/ichi2/anki/previewer/TemplatePreviewerViewModel.kt

@@ -45,6 +45,7 @@ import org.jetbrains.annotations.VisibleForTesting
 class TemplatePreviewerViewModel(
     savedStateHandle: SavedStateHandle,
 ) : CardViewerViewModel(savedStateHandle) {
+    override val cardMediaPlayer by lazy { createCardMediaPlayer() }
     private val notetype: NotetypeJson
     private val fillEmpty: Boolean
     private val isCloze: Boolean

AnkiDroid/src/main/java/com/ichi2/anki/ui/windows/reviewer/ReviewerViewModel.kt

@@ -84,6 +84,7 @@ class ReviewerViewModel(
     ChangeManager.Subscriber,
     BindingProcessor<ReviewerBinding, ViewerAction>,
     AutoAdvance.ActionListener {
+    override val cardMediaPlayer by lazy { createCardMediaPlayer() }
     private var queueState: Deferred<CurrentQueueState?> =
         asyncIO {
             withCol { sched.currentQueueState() }

AnkiDroid/src/test/java/com/ichi2/anki/previewer/PreviewerViewModelTest.kt

@@ -19,18 +19,22 @@ import androidx.lifecycle.SavedStateHandle
 import androidx.test.ext.junit.runners.AndroidJUnit4
 import com.ichi2.anki.Flag
 import com.ichi2.anki.browser.IdsFile
+import com.ichi2.anki.cardviewer.CardMediaPlayer
 import com.ichi2.anki.servicelayer.NoteService
 import com.ichi2.anki.utils.ext.flag
 import com.ichi2.testutils.JvmTest
 import com.ichi2.testutils.common.Flaky
 import com.ichi2.testutils.common.OS
 import io.mockk.coEvery
+import io.mockk.coVerify
 import io.mockk.every
 import io.mockk.mockk
 import io.mockk.spyk
+import io.mockk.verify
 import kotlinx.coroutines.flow.first
 import kotlinx.coroutines.test.TestScope
 import kotlinx.coroutines.test.advanceUntilIdle
+import kotlinx.coroutines.test.runTest
 import org.junit.Assert.assertEquals
 import org.junit.Assert.assertFalse
 import org.junit.Assert.assertTrue
@@ -42,7 +46,13 @@ import org.junit.runner.RunWith
 class PreviewerViewModelTest : JvmTest() {
     private val idsFile: IdsFile = mockk()
 
+    private class TestPreviewerViewModel(
+        savedStateHandle: SavedStateHandle,
+        override val cardMediaPlayer: CardMediaPlayer,
+    ) : PreviewerViewModel(savedStateHandle)
+
     private lateinit var viewModel: PreviewerViewModel
+    private lateinit var mockMediaPlayer: CardMediaPlayer
 
     private fun TestScope.onNextButtonClick() {
         viewModel.onNextButtonClick()
@@ -79,9 +89,9 @@ class PreviewerViewModelTest : JvmTest() {
                 set(PreviewerFragment.CARD_IDS_FILE_ARG, idsFile)
             }
 
-        viewModel = spyk(PreviewerViewModel(savedStateHandle))
-        // the default implementation requires the Collection media directory,
-        // which needs Robolectric with CollectionStorageMode.IN_MEMORY_WITH_MEDIA or ON_DISK
+        mockMediaPlayer = mockk(relaxed = true)
+        viewModel = spyk(TestPreviewerViewModel(savedStateHandle, mockMediaPlayer))
+
         coEvery { viewModel.prepareCardTextForDisplay(any()) } answers { firstArg() }
     }
 
@@ -270,4 +280,26 @@ class PreviewerViewModelTest : JvmTest() {
             onSliderChange(sliderPosition = 2)
             assertEquals("Index should update for valid input", 1, viewModel.currentIndex.value)
         }
+
+    @Test
+    fun `audio stops when changing sides`() =
+        runTest {
+            viewModel.onPageFinished(false)
+            viewModel.showingAnswer.value = false
+
+            // 1. Next Button (Question -> Answer)
+            onNextButtonClick()
+            coVerify(atLeast = 1) { mockMediaPlayer.stop() }
+
+            // Reset mocks
+            io.mockk.clearMocks(mockMediaPlayer, answers = false, recordedCalls = true, childMocks = false)
+
+            onPreviousButtonClick()
+            coVerify(atLeast = 1) { mockMediaPlayer.stop() }
+
+            io.mockk.clearMocks(mockMediaPlayer, answers = false, recordedCalls = true, childMocks = false)
+
+            toggleBackSideOnly()
+            coVerify(atLeast = 1) { mockMediaPlayer.stop() }
+        }
 }