MediaController

public class MediaController
extends Object implements Closeable

java.lang.Object
   ↳ androidx.media2.session.MediaController


Allows an app to interact with an active MediaSession or a MediaSessionService which would provide MediaSession. Media buttons and other commands can be sent to the session.

MediaController objects are thread-safe.

Topics covered here:

  1. Controller Lifecycle
  2. Controlling the MediaSession in the same process

Controller Lifecycle

When a controller is created with the SessionToken for a MediaSession (i.e. session token type is SessionToken.TYPE_SESSION), the controller will connect to the specific session.

When a controller is created with the SessionToken for a MediaSessionService (i.e. session token type is SessionToken.TYPE_SESSION_SERVICE or SessionToken.TYPE_LIBRARY_SERVICE), the controller binds to the service for connecting to a MediaSession in it. MediaSessionService will provide a session to connect.

When a controller connects to a session, MediaSession.SessionCallback.onConnect(MediaSession, MediaSession.ControllerInfo) will be called to either accept or reject the connection. Wait MediaController.ControllerCallback.onConnected(MediaController, SessionCommandGroup) or MediaController.ControllerCallback.onDisconnected(MediaController) for the result.

When the connected session is closed, the controller will receive MediaController.ControllerCallback.onDisconnected(MediaController).

When you're done, use close() to clean up resources. This also helps session service to be destroyed when there's no controller associated with it.

Controlling the MediaSession in the same process

When you control the MediaSession and its SessionPlayer, it's recommended to use them directly rather than creating MediaController. However, if you need to use MediaController in the same process, be careful not to block session callback executor's thread. Here's an example code that would never return due to the thread issue.

 // Code runs on the main thread.
 MediaSession session = new MediaSession.Builder(context, player)
    .setSessionCallback(sessionCallback, Context.getMainExecutor(context)).build();
 MediaController controller = new MediaController.Builder(context)
    .setSessionToken(session.getToken())
    .setControllerCallback(Context.getMainExecutor(context), controllerCallback)
    .build();

 // This will hang and never return.
 controller.play().get();
When a session gets a command from a controller, the session's MediaSession.SessionCallback.onCommandRequest(MediaSession, MediaSession.ControllerInfo, SessionCommand) would be executed on the session's callback executor to decide whether to ignore or handle the incoming command. To do so, the session's callback executor shouldn't be blocked to handle the incoming calls. However, if you call Future.get() on the thread for the session callback executor, then your call wouldn't be executed and never return.

To avoid such issue, don't block the session callback executor's thread. Creating a dedicated thread for the session callback executor would be helpful. See Executors.newSingleThreadExecutor() for creating a new thread.

Summary

Nested classes

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