media3-cast-integration

Imported from android/skills (media/media3-cast-integration/SKILL.md). Install upstream with npx skills add android/skills --skill media3-cast-integration. Copyright stays with the author (Complete terms in LICENSE.txt).

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• Google Cast SDK: Legacy casting SDK in maintenance mode, superseded by Jetpack Media3.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

• 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.
  • 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.