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• Google Cast SDK: Legacy casting SDK in maintenance mode, superseded by Jetpack Media3.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.
• 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:1.11.0")

• 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 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.
• Declare a custom OptionsProvider only if explicitly requested. See Customize CastOptions.
• 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.
• 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 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) @Composable fun MainScreen() { val player = rememberMediaController() val deviceInfo = rememberDeviceInfo(player) player?.let { activePlayer -> key(deviceInfo) { PlayerScreen(player = activePlayer) } } }

@Composable private fun rememberMediaController(): Player? { // Logic to connect MediaController to MediaSession and release it }

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