Media3 Cast Integration

Prerequisites

• Jetpack Media3 version must be >= 1.9.0. Cast isn't available in lower versions.

Glossary

• CastPlayer : Media3 Player that controls playback on both local and remote Cast devices.
• RemoteCastPlayer : Media3 Player that communicates with a Cast receiver, only used for remote playback.
• Google Cast SDK: Legacy casting SDK in maintenance mode, superseded by Jetpack Media3.
• OptionsProvider : Interface providing configuration options to initialize GMS CastContext.

Common guidelines

• Legacy Google Cast SDK is in maintenance mode.
• For new Cast setups:
  • You must use Jetpack Media3 Cast [blocked].
  • You mustn't use legacy Cast SDK unless explicitly requested.

Step 1: Set up dependencies

To complete this step, you MUST ensure the following:

• In the app-level build file, declare the media3-cast dependency version 1.9.0 or higher.

  implementation("androidx.media3:media3-cast:1.11.1")

• Ensure required Media3 dependencies are present:

  • androidx.media3:media3-exoplayer
  • androidx.media3:media3-session
  • androidx.media3:media3-ui-compose

• If the application uses legacy Views, add media3-ui.

• Enforce the same versions across all Media3 dependencies.

• Use configurations in "Add build dependencies" section of Getting started with CastPlayer [blocked] as the source of truth.

• For apps without an existing Cast integration:

  • Verify legacy Cast SDK (libs.play.services.cast.framework) is absent.

• If Migrating from Legacy Cast SDK:

  • Add Media3 Cast dependencies first.
  • Keep existing legacy dependencies untouched at this stage to prevent compilation errors.

Step 2: Update the manifest

To complete this step, you MUST ensure the following:

• Inside the manifest's <application> tag, declare the Cast options provider.
• Use DefaultCastOptionsProvider by default. See the "OptionsProvider" section in Getting started with CastPlayer [blocked].
• Declare a custom OptionsProvider only if explicitly requested. See Customize CastOptions [blocked].
• Ensure INTERNET permission is present. Don't add any unnecessary permissions.
• If Migrating from Legacy Cast SDK:
  • Don't delete existing custom options provider files or manifest entries.

Step 3: Implement the player and service

Architecture baseline

Before integrating Media3 Cast, an existing app follows one of two setups:

• Local-only playback: Uses Media3 ExoPlayer only to support local playback.
• Legacy Cast setup: Uses ExoPlayer for local playback, alongside a Player wrapper over the legacy RemoteMediaClient for remote playback. The UI interfaces with a MediaSession interacting with a ForwardingPlayer, which finally routes controls to either local or remote playback.

To complete this step, you MUST ensure the following:

• Inside the application's MediaSessionService (or MediaLibraryService) onCreate() method, initialize ExoPlayer and CastPlayer.
• Use CastPlayer by default unless RemoteCastPlayer is explicitly requested. See the "Build a CastPlayer" section in Getting started with CastPlayer [blocked].
• For CastPlayer, pass the instance directly to MediaSession.Builder.
• Replace all legacy forwarding player wrappers.
• Don't delete legacy class files yet to prevent compilation errors during migration.

Advanced: RemoteCastPlayer

• Use RemoteCastPlayer only if explicitly requested by user.

• Initialize MediaSession with localPlayer and set a SessionAvailabilityListener on RemoteCastPlayer to transfer playback state on Cast session availability changes:

  class PlaybackService : MediaSessionService() { private var mediaSession: MediaSession? = null private lateinit var localPlayer: ExoPlayer private lateinit var remotePlayer: RemoteCastPlayer

  override fun onCreate() {  super.onCreate()
    localPlayer = ExoPlayer.Builder(this).build()  remotePlayer = RemoteCastPlayer.Builder(this).build()  mediaSession = MediaSession.Builder(this, localPlayer).build()
    remotePlayer.setSessionAvailabilityListener(    object : SessionAvailabilityListener {      override fun onCastSessionAvailable() {        transferPlaybackState(localPlayer, remotePlayer)      }
        override fun onCastSessionUnavailable() {        transferPlaybackState(remotePlayer, localPlayer)      }    }  )}
  private fun transferPlaybackState(previousPlayer: Player, newPlayer: Player) {  if (previousPlayer.mediaItemCount > 0) {    val transferStateBuilder = PlayerTransferState.builderFromPlayer(previousPlayer)    if (previousPlayer.playbackState == Player.STATE_ENDED ||        previousPlayer.currentPosition == C.TIME_END_OF_SOURCE) {      transferStateBuilder.setCurrentMediaItemIndex(0)      transferStateBuilder.setCurrentPosition(0)    }    transferStateBuilder.build().setToPlayer(newPlayer)  }
    previousPlayer.stop()  previousPlayer.clearMediaItems()  newPlayer.prepare()  mediaSession?.setPlayer(newPlayer)}

  }

Step 4: Set up the UI

Compose-based UI

To complete this step, you MUST ensure the following:

• See the "Add a MediaRouteButton Composable to the Player" section in Getting started with CastPlayer [blocked] for Compose integration guidelines.

• Use the MediaRouteButton composable from androidx.media3.cast package.

• Don't use AndroidView in the Compose UI hierarchy.

• Place MediaRouteButton in an area next to playback controls. Don't hide it behind system UI.

• Don't use PlayerSurface for custom player UI. Use the Material3 Player composable.

• Force recomposition on playback location shifts to ensure UI sync. Use key constraints on DeviceInfo changes:

  @OptIn(UnstableApi::class)@Composablefun MainScreen() {   val player = rememberMediaController()   val deviceInfo = rememberDeviceInfo(player)   player?.let { activePlayer -> key(deviceInfo) { PlayerScreen(player = activePlayer) } }}
  @Composableprivate fun rememberMediaController(): Player? {   // Logic to connect MediaController to MediaSession and release it}
  @Composableprivate fun rememberDeviceInfo(player: Player?): DeviceInfo? {   var deviceInfo by remember(player) { mutableStateOf(player?.deviceInfo) }   DisposableEffect(player) {       val activePlayer = player ?: return@DisposableEffect onDispose {}       deviceInfo = activePlayer.deviceInfo       val listener = object : Player.Listener {           override fun onDeviceInfoChanged(info: DeviceInfo) {               deviceInfo = info           }       }      activePlayer.addListener(listener)      onDispose { activePlayer.removeListener(listener) }   }   return deviceInfo}

View-based UI

To complete this step, you MUST ensure the following:

• For View-based UI setups, see the "Add UI elements" section in Getting started with CastPlayer [blocked].

• Casting Activities must extend AppCompatActivity or FragmentActivity and use a Theme.AppCompat descendant.

• Ensure the AppCompat theme has a visible ActionBar if adding MediaRouteButton to the options menu.

• Replace all instances and imports of CastButtonFactory with MediaRouteButtonFactory.

• Rebind PlayerView.player references upon onDeviceInfoChanged events to prevent black screens or UI freezes:

  private val playerListener: Player.Listener =  object : Player.Listener {    override fun onDeviceInfoChanged(deviceInfo: DeviceInfo) {      // Resetting to null bypasses PlayerView.setPlayer()'s instance equality check      // (this.player == player), forcing it to re-bind the video surface to the controller.      playerView.player = null      playerView.player = controller    }  }

• Migration to Compose:

  • Don't use AndroidView to wrap the legacy PlayerView.
  • Implement Material3 Player composable and MediaRouteButton composable as per Getting started with CastPlayer [blocked].
  • Remove legacy XML layout declarations, menu files, and View component references.

Step 5: Clean up legacy Cast SDK code

[!WARNING] Warning: Don't perform cleanup directly. Remove legacy files and dependencies only when explicitly requested by the user.

To complete this step, you MUST ensure the following:

• Remove legacy GMS Cast SDK (libs.play.services.cast.framework) and MediaRouter (libs.androidx.mediarouter) dependencies.
• Delete custom OptionsProvider classes and manifest entries if DefaultCastOptionsProvider is adopted.
• Remove legacy MediaTransferReceiver manifest declarations if present.
• Remove all references to legacy Cast SDK components such as legacy helper wrappers, forwarding players, and RemoteMediaClient interfaces.
• Delete legacy View XML layouts, menu files, and references to PlayerView if the migration to Compose is complete.