[b/417361559] Replace Toast with Snackbar in demo composition

This PR addresses the TODO in `CompositionPreviewActivity` by replacing the `Toast` with a `Snackbar`.

Author: MGaetan89

demos/composition/build.gradle

@@ -69,7 +69,6 @@ dependencies {
     implementation project(modulePrefix + 'lib-ui')
     implementation project(modulePrefix + 'lib-ui-compose')
     implementation 'androidx.annotation:annotation:' + androidxAnnotationVersion
-    implementation 'androidx.lifecycle:lifecycle-livedata:' + androidxLifecycleVersion
     implementation 'androidx.lifecycle:lifecycle-viewmodel:' + androidxLifecycleVersion
     implementation 'androidx.activity:activity-compose:1.9.0'
     implementation platform('androidx.compose:compose-bom:2024.12.01')

demos/composition/src/main/java/androidx/media3/demo/composition/CompositionPreviewActivity.kt

@@ -20,7 +20,6 @@ import android.os.Build.VERSION.SDK_INT
 import android.os.Bundle
 import android.os.LocaleList
 import android.util.Log
-import android.widget.Toast
 import androidx.activity.compose.BackHandler
 import androidx.activity.compose.setContent
 import androidx.activity.enableEdgeToEdge
@@ -61,6 +60,8 @@ import androidx.compose.material3.MaterialTheme
 import androidx.compose.material3.OutlinedButton
 import androidx.compose.material3.RadioButton
 import androidx.compose.material3.Scaffold
+import androidx.compose.material3.SnackbarHost
+import androidx.compose.material3.SnackbarHostState
 import androidx.compose.material3.Switch
 import androidx.compose.material3.Text
 import androidx.compose.material3.adaptive.ExperimentalMaterial3AdaptiveApi
@@ -70,6 +71,7 @@ import androidx.compose.material3.adaptive.layout.SupportingPaneScaffold
 import androidx.compose.material3.adaptive.layout.ThreePaneScaffoldRole
 import androidx.compose.material3.adaptive.navigation.rememberSupportingPaneScaffoldNavigator
 import androidx.compose.runtime.Composable
+import androidx.compose.runtime.LaunchedEffect
 import androidx.compose.runtime.collectAsState
 import androidx.compose.runtime.getValue
 import androidx.compose.runtime.mutableStateOf
@@ -125,17 +127,22 @@ class CompositionPreviewActivity : AppCompatActivity() {
       CompositionPreviewViewModelFactory(application, compositionLayout)
     }
 
-    // TODO(b/417361559): Replace Toast with Snackbar
-    viewModel.toastMessage.observe(this) { newMessage ->
-      newMessage?.let {
-        viewModel.toastMessage.value = null
-        Toast.makeText(this, it, Toast.LENGTH_SHORT).show()
+    setContent {
+      val snackbarHostState = remember { SnackbarHostState() }
+      val snackbarMessage = viewModel.snackbarMessage
+
+      LaunchedEffect(snackbarMessage) {
+        if (snackbarMessage != null) {
+          snackbarHostState.showSnackbar(snackbarMessage)
+          viewModel.snackbarMessage = null
+        }
       }
-    }
 
-    setContent {
       CompositionDemoTheme {
-        Scaffold(modifier = Modifier.fillMaxSize()) { innerPadding ->
+        Scaffold(
+          modifier = Modifier.fillMaxSize(),
+          snackbarHost = { SnackbarHost(hostState = snackbarHostState) },
+        ) { innerPadding ->
           val scope = rememberCoroutineScope()
           val navigator = rememberSupportingPaneScaffoldNavigator()
 

demos/composition/src/main/java/androidx/media3/demo/composition/CompositionPreviewViewModel.kt

@@ -24,7 +24,6 @@ import androidx.compose.runtime.mutableStateListOf
 import androidx.compose.runtime.mutableStateOf
 import androidx.compose.runtime.setValue
 import androidx.lifecycle.AndroidViewModel
-import androidx.lifecycle.MutableLiveData
 import androidx.lifecycle.ViewModel
 import androidx.lifecycle.ViewModelProvider
 import androidx.media3.common.Effect
@@ -79,7 +78,7 @@ class CompositionPreviewViewModel(application: Application, val compositionLayou
     var applyEffects: MutableState<Boolean>,
   )
 
-  var toastMessage = MutableLiveData<String?>(null)
+  var snackbarMessage by mutableStateOf<String?>(null)
 
   var compositionPlayer by mutableStateOf(createCompositionPlayer())
 
@@ -143,7 +142,7 @@ class CompositionPreviewViewModel(application: Application, val compositionLayou
 
   fun addItem(index: Int) {
     selectedMediaItems.add(mediaItemOptions[index].copy(applyEffects = mutableStateOf(false)))
-    toastMessage.value = "Added item: ${mediaItemOptions[index].title}"
+    snackbarMessage = "Added item: ${mediaItemOptions[index].title}"
   }
 
   fun removeItem(index: Int) {
@@ -173,7 +172,7 @@ class CompositionPreviewViewModel(application: Application, val compositionLayou
       outputFile =
         createExternalCacheFile("composition-preview-" + Clock.DEFAULT.elapsedRealtime() + ".mp4")
     } catch (e: IOException) {
-      toastMessage.value = "Aborting export! Unable to create output file: $e"
+      snackbarMessage = "Aborting export! Unable to create output file: $e"
       Log.e(TAG, "Aborting export! Unable to create output file: ", e)
       return
     }
@@ -234,7 +233,7 @@ class CompositionPreviewViewModel(application: Application, val compositionLayou
               exportException: ExportException,
             ) {
               exportStopwatch.stop()
-              toastMessage.value = "Export error: $exportException"
+              snackbarMessage = "Export error: $exportException"
               Log.e(TAG, "Export error", exportException)
               Log.d(TAG, DebugTraceUtil.generateTraceSummary())
               exportResultInformation = EXPORT_ERROR_MESSAGE
@@ -410,7 +409,7 @@ class CompositionPreviewViewModel(application: Application, val compositionLayou
     player.addListener(
       object : Player.Listener {
         override fun onPlayerError(error: PlaybackException) {
-          toastMessage.value = "Preview error: $error"
+          snackbarMessage = "Preview error: $error"
           Log.e(TAG, "Preview error", error)
         }
       }