Using Media Style Notifications with Media Session Controls

*** Some content from this post is deprecated in later versions of Android ***

     Android Lollipop has brought with it many new features, one of which is lock screen notifications. Up until this point, lock screen media controls had to be implemented through the use of a RemoteView, and media control notifications had to be built with custom views. In this tutorial I will go over using the new MediaStyle for notifications and interacting with a MediaSession for controlling media playback states. All code for this tutorial can be found on GitHub.

    The very first thing that we're going to need to do is set the MEDIA_CONTENT_CONTROL permission in AndroidManifest.xml. This will allow us to use our lock screen notification to control media.

    <permission android:name="android.permission.MEDIA_CONTENT_CONTROL" />

    For this example we're going to use a background service to controls our media and build/interact with the new notifications. Our MainActivity is going to be very straight forward and simply start our service with an action telling the service to build a playing state notification

    Intent intent = new Intent( getApplicationContext(), MediaPlayerService.class );
    intent.setAction( MediaPlayerService.ACTION_PLAY );
    startService( intent );

    Next we're going to want to start fleshing out MediaPlayerService. At the top of the class we're going to define a set of strings that we will use to implement notification actions, and also define the objects that we'll use throughout the class.

    public static final String ACTION_PLAY = "action_play";
    public static final String ACTION_PAUSE = "action_pause";
    public static final String ACTION_REWIND = "action_rewind";
    public static final String ACTION_FAST_FORWARD = "action_fast_foward";
    public static final String ACTION_NEXT = "action_next";
    public static final String ACTION_PREVIOUS = "action_previous";
    public static final String ACTION_STOP = "action_stop";

    private MediaPlayer mMediaPlayer;
    private MediaSessionManager mManager;
    private MediaSession mSession;
    private MediaController mController;

   When the service receives an intent, it'll immediately go through onStartCommand. This method only does two simple things: if our objects have not been initialized, it'll call initMediaSession to set them up, and then the intent will be passed to handleIntent.

    initMediaSession initializes the objects that we defined earlier. MediaPlayer handles media playback (not used in this example, but in an actual app it would be), the MediaSessionManager helps maintain the MediaSession, MediaSession is used for keeping track of media states, and the MediaController handles transitioning between media states and calling MediaPlayer methods.

    mMediaPlayer = new MediaPlayer();
    mManager = (MediaSessionManager) getSystemService(Context.MEDIA_SESSION_SERVICE);
    mSession = mManager.createSession("sample session");
    mController = MediaController.fromToken( mSession.getSessionToken() );

    The next thing initMediaSession does is add TransportControlCallbacks that we can call in order to control the MediaPlayer and display new notifications.

    mSession.addTransportControlsCallback( new MediaSession.TransportControlsCallback() {
        @Override
        public void onPlay() {
            super.onPlay();
            Log.e( "MediaPlayerService", "onPlay");
            buildNotification( generateAction( android.R.drawable.ic_media_pause, "Pause", ACTION_PAUSE ) );
        }

        @Override
        public void onPause() {
            super.onPause();
            Log.e( "MediaPlayerService", "onPause");
            buildNotification(generateAction(android.R.drawable.ic_media_play, "Play", ACTION_PLAY));
        }

        @Override
        public void onSkipToNext() {
            super.onSkipToNext();
            Log.e( "MediaPlayerService", "onSkipToNext");
            //Change media here
            buildNotification( generateAction( android.R.drawable.ic_media_pause, "Pause", ACTION_PAUSE ) );
        }

        @Override
        public void onSkipToPrevious() {
            super.onSkipToPrevious();
            Log.e( "MediaPlayerService", "onSkipToPrevious");
            //Change media here
            buildNotification( generateAction( android.R.drawable.ic_media_pause, "Pause", ACTION_PAUSE ) );
        }

        @Override
        public void onFastForward() {
            super.onFastForward();
            Log.e( "MediaPlayerService", "onFastForward");
            //Manipulate current media here
        }

        @Override
        public void onRewind() {
            super.onRewind();
            Log.e( "MediaPlayerService", "onRewind");
            //Manipulate current media here
        }

        @Override
        public void onStop() {
            super.onStop();
            Log.e( "MediaPlayerService", "onStop");
            //Stop media player here
            NotificationManager notificationManager = (NotificationManager) getApplicationContext().getSystemService(Context.NOTIFICATION_SERVICE);
            notificationManager.cancel( 1 );
            Intent intent = new Intent( getApplicationContext(), MediaPlayerService.class );
            stopService( intent );
        }

        @Override
        public void onSeekTo(long pos) {
            super.onSeekTo(pos);
        }

        @Override
        public void onSetRating(Rating rating) {
            super.onSetRating(rating);
        }
    });

    These control methods are called in handleIntent. When an intent is received by the service, handleIntent extracts the action associated with that intent to determine which transport control method should be called

    private void handleIntent( Intent intent ) {
        if( intent == null || intent.getAction() == null )
            return;

        String action = intent.getAction();

        if( action.equalsIgnoreCase( ACTION_PLAY ) ) {
            mController.getTransportControls().play();
        } else if( action.equalsIgnoreCase( ACTION_PAUSE ) ) {
            mController.getTransportControls().pause();
        } else if( action.equalsIgnoreCase( ACTION_FAST_FORWARD ) ) {
            mController.getTransportControls().fastForward();
        } else if( action.equalsIgnoreCase( ACTION_REWIND ) ) {
            mController.getTransportControls().rewind();
        } else if( action.equalsIgnoreCase( ACTION_PREVIOUS ) ) {
            mController.getTransportControls().skipToPrevious();
        } else if( action.equalsIgnoreCase( ACTION_NEXT ) ) {
            mController.getTransportControls().skipToNext();
        } else if( action.equalsIgnoreCase( ACTION_STOP ) ) {
            mController.getTransportControls().stop();
        }
    }

    As can be seen in the TransportControlCallbacks, we call buildNotification with another method called generateAction. Actions are used by the MediaStyle notification to populate the buttons at the bottom of the notification and launch intents when pressed. generateAction simply accepts the icon that the notification will use for that button, a title for the button and a string that will be used as the action identifier in handleIntent. With this information, generateAction is able to construct a pendingIntent before assigning it to an action that is then returned.

    private Notification.Action generateAction( int icon, String title, String intentAction ) {
        Intent intent = new Intent( getApplicationContext(), MediaPlayerService.class );
        intent.setAction( intentAction );
        PendingIntent pendingIntent = PendingIntent.getService(getApplicationContext(), 1, intent, 0);
        return new Notification.Action.Builder( icon, title, pendingIntent ).build();
    }

    buildNotification is where we actually implement the MediaStyle notification. The first thing we do is create a new Notification.MediaStyle style, then start building the rest of the notification through using Notification.Builder. This notification simply contains a pendingIntent that would stop our media when the notification is dismissed, a title, content text, a small icon and the style.

private void buildNotification( Notification.Action action ) {
    Notification.MediaStyle style = new Notification.MediaStyle();

    Intent intent = new Intent( getApplicationContext(), MediaPlayerService.class );
    intent.setAction( ACTION_STOP );
    PendingIntent pendingIntent = PendingIntent.getService(getApplicationContext(), 1, intent, 0);
    Notification.Builder builder = new Notification.Builder( this )
            .setSmallIcon( R.drawable.ic_launcher )
            .setContentTitle( "Media Title" )
            .setContentText( "Media Artist" )
            .setDeleteIntent( pendingIntent )
            .setStyle( style );

    Next we can add our buttons to the notification through the use of Builder.addAction. It should be noted that MediaStyle notifications only support up to five different actions. Each of our actions will be generated through the generateAction method described above.

    builder.addAction( generateAction( android.R.drawable.ic_media_previous, "Previous", ACTION_PREVIOUS ) );
    builder.addAction( generateAction( android.R.drawable.ic_media_rew, "Rewind", ACTION_REWIND ) );
    builder.addAction( action );
    builder.addAction( generateAction( android.R.drawable.ic_media_ff, "Fast Foward", ACTION_FAST_FORWARD ) );
    builder.addAction( generateAction( android.R.drawable.ic_media_next, "Next", ACTION_NEXT ) );

    The last thing this method does is actually construct the notification and post it to the system

    NotificationManager notificationManager = (NotificationManager) getSystemService( Context.NOTIFICATION_SERVICE );
    notificationManager.notify( 1, builder.build() );

    Now that the notification and sessions are implementing and working, the final thing we need to take into account is releasing our MediaSession once the media player and service have been stopped.

    @Override
    public boolean onUnbind(Intent intent) {
        mSession.release();
        return super.onUnbind(intent);
    }

    And with that we now have a fully working MediaStyle notification on our lock screen and in the notification drawer that takes advantage of MediaSession for playback control. Enjoy!

A Guide to the Android Wear Message API

I originally wrote this post for the good folks over at Binpress.com

While Android Wear provides a lot of great features, such as notifications, out of the box, its real potential lies in the ability to create native apps that communicate with a paired smartphone. Luckily, Android Wear comes with a few new APIs to help make this communication a lot smoother for developers: the Message API, Node API and DataLayer API. Each of these has their own unique purpose; the Message API is designed for "fire and forget it" types of messages, the DataLayer API supports syncing data between a smartphone and a wearable, and the Node API handles events related to local and connected device nodes.

For this tutorial I'll cover using the Message API to send data from a smartphone to an Android Wear device. We'll start a watch activity by using a WearableListenerService and display text in a ListView through the MessageApi.MessageListener interface, though all three APIs are used in a similar way. All sample code for this tutorial can be found on GitHub.

To start, create a project in Android Studio that has both a mobile and wear module:

Once your project and modules are created, you can start building the mobile side of your application. The sample project contains simple ListView, EditText and Button views that allow the user to enter text and, when the Button is pressed, display it in the ListView while also sending that text to the wearable.

To start, open AndroidManifest.xml in the mobile module and add a meta-data tag for Google Play Services

<meta-data android:name="com.google.android.gms.version" android:value="@integer/google_play_services_version" />

Next, we can focus on the mobile MainActivity class. The first thing we need to do is connect the GoogleApiClient and implement the GoogleApiClient.ConnectionCallbacks interface:

private void initGoogleApiClient() {
    mApiClient = new GoogleApiClient.Builder( this )
            .addApi( Wearable.API )
            .addConnectionCallbacks( this )
            .build();

    if( mApiClient != null && !( mApiClient.isConnected() || mApiClient.isConnecting() ) )
        mApiClient.connect();
}

When the GoogleApiClient has finished connecting, onConnected will be called. When it is, we'll send a message through the Message API to a WearableListenerService (implemented later in this tutorial) running on the Wear in order to start our watch activity.

@Override
public void onConnected(Bundle bundle) {
    sendMessage( START_ACTIVITY, "" );
}

...where START_ACTIVITY is a string value that must begin with /, denoting a message path.

private static final String START_ACTIVITY = "/start_activity";

Aside from our initial message, we also want a message to be sent when our 'send' button is pressed. This is done through a simple OnClickListener that uses a different path value of /message and sends the text present in the EditText at the bottom of the screen.

mSendButton.setOnClickListener( new View.OnClickListener() {
    @Override
    public void onClick(View view) {
        String text = mEditText.getText().toString();
        if (!TextUtils.isEmpty(text)) {
            mAdapter.add(text);
            mAdapter.notifyDataSetChanged();

            sendMessage(WEAR_MESSAGE_PATH, text);
        }
    }
});

The sendMessage method is where we really start to see how we interact with the new Android Wear APIs. In order to send a message to the Wear, we must first use the Node API to get a list of nodes connected to the device. Once we have this list, we send a message to each node using MessageAPI with references to the GoogleApiClient, node ID, the path used to determine the type of message being sent, and the message payload as a byte array. A MessageApi.SendMessageResult is returned that can be used to determine if a message was successfully sent to the current node. Once the message is sent, we clear the EditText view to allow the user to enter more text.

private void sendMessage( final String path, final String text ) {
    new Thread( new Runnable() {
        @Override
        public void run() {
            NodeApi.GetConnectedNodesResult nodes = Wearable.NodeApi.getConnectedNodes( mApiClient ).await();
            for(Node node : nodes.getNodes()) {
                MessageApi.SendMessageResult result = Wearable.MessageApi.sendMessage(
                        mApiClient, node.getId(), path, text.getBytes() ).await();
            }

            runOnUiThread( new Runnable() {
                @Override
                public void run() {
                    mEditText.setText( "" );
                }
            });
        }
    }).start();
}

Finally in onDestroy, we need to disconnect from GoogleApiClient.

@Override
protected void onDestroy() {
    super.onDestroy();
    mApiClient.disconnect();
}

Now that the mobile MainActivity is ready, it's time to move into the wear module. First we'll want to create a class that extends from WearableListenerService, which is a service that implements the three Wear communication APIs. For our purposes we only need to override the onMessageReceived method. In this method we check the path that was sent over the MessageApi to determine the type of message, and then, if appropriate, fire off an intent to our wear MainActivity to bring our application to the forefront.

private static final String START_ACTIVITY = "/start_activity";

@Override
public void onMessageReceived(MessageEvent messageEvent) {
    if( messageEvent.getPath().equalsIgnoreCase( START_ACTIVITY ) ) {
        Intent intent = new Intent( this, MainActivity.class );
        intent.addFlags( Intent.FLAG_ACTIVITY_NEW_TASK );
        startActivity( intent );
    } else {
        super.onMessageReceived(messageEvent);
    }
}

Once we're done implementing our service, we need to add it into the wear AndroidManifest.xml file.

<service android:name=".WearMessageListenerService">
    <intent-filter>
        <action android:name="com.google.android.gms.wearable.BIND_LISTENER" />
    </intent-filter>
</service>

As mentioned earlier, there are two ways to receive a message on Android Wear. The next way is implementing MessageApi.MessageListener in our Wear MainActivity. To start, we need to connect GoogleApiClient in the same way as our mobile application. In the onConnected callback, we add our wearable listener to the api client

@Override
public void onConnected(Bundle bundle) {
    Wearable.MessageApi.addListener( mApiClient, this );
}

Next, we simply override the onMessageReceived method from the MessageListener interface, check the path value to determine if we want to take action, and then add the payload text to our adapter to display the text in our wear ListView

@Override
public void onMessageReceived( final MessageEvent messageEvent ) {
    runOnUiThread( new Runnable() {
        @Override
        public void run() {
            if( messageEvent.getPath().equalsIgnoreCase( WEAR_MESSAGE_PATH ) ) {
                mAdapter.add(new String(messageEvent.getData()));
                mAdapter.notifyDataSetChanged();
            }
        }
    });
}

This will display the text from our mobile app on the wearable, as seen below (the screen shot was taken from a Moto 360, hence the cut off portion at the bottom).

And with that we now have a working communication channel from a smartphone to a paired Android Wear device. I hope this tutorial helps you build your own applications. Good luck!