Media playback the right way Ian Lake Developer Advocate, Google 

About me ~5 years of Android Development experience Previously at Phunware, Facebook Developer Advocate at Google ● Advanced Android Udacity Course ● Android Development Patterns 

Media playback Specifically audio Video: github.com/googlecast/CastCompanionLibrary-android 

User expectations 

Background playback = Service 

Important events in media playback Created Playing Paused Stopped Destroyed 

Playing audio MediaPlayer* *Or ExoPlayer: github.com/google/ExoPlayer Created Playing Paused Stopped Destroyed MediaPlayer new prepare -> play pause stop release Mission Accomplished! 

Media playback the right way What do we still need? 

Audio Focus // Request audio focus AudioManager audioManager = (AudioManager) getSystemService(Context.AUDIO_SERVICE); int result = audioManager.requestAudioFocus( mOnAudioFocusChangeListener, AudioManager.STREAM_MUSIC, AudioManager.AUDIOFOCUS_GAIN); if (result == AudioManager.AUDIOFOCUS_REQUEST_GRANTED) { // Proceed with the playing of glorious music } // On stop audioManager.abandonAudioFocus( mOnAudioFocusChangeListener); Ensure apps don’t talk over one another Hold audio focus until we’ve stopped playback 

OnAudioFocusChangeListener ● AUDIOFOCUS_LOSS ○ Stop Playback ● AUDIOFOCUS_LOSS_TRANSIENT ○ Pause ● AUDIOFOCUS_LOSS_TRANSIENT_CAN_DUCK ○ Lower volume (keep playing) ● AUDIOFOCUS_GAIN ○ Play at full volume (if previously paused) 

Lifecycle of media playback Created Playing Paused Stopped Destroyed MediaPlayer new prepare -> play pause stop release Audio Focus request focus abandon focus Done! Not quite... 

private BroadcastReceiver mNoisyReceiver = new BroadcastReceiver() { @Override public void onReceive(Context context, Intent intent) { // Pause the music } }; // On Play IntentFilter filter = new IntentFilter(AudioManager.ACTION_AUDIO_BECOMING_NOISY)); registerReceiver(mNoisyReceiver, filter); // On Pause unregisterReceiver(mNoisyReceiver); ACTION_AUDIO_BECOMING_NOISY 

Lifecycle of media playback Created Playing Paused Stopped Destroyed MediaPlayer new prepare -> play pause stop release Audio Focus request focus abandon focus NOISY register unregister Minimum viable product? 

Controls everywhere 

Headphones and bluetooth controls ‘Media buttons’ android.intent.action.MEDIA_BUTTON broadcasts sent by the system Use Support Library provided MediaButtonReceiver 

But … not working? 

Preferred media button receiver Becoming the chosen one 

Your app <--> media APIs Callbacks MediaSessionCompat // In onCreate() mMediaSession = new MediaSessionCompat( context, LOG_TAG); mMediaSession.setFlags( MediaSessionCompat. FLAG_HANDLES_MEDIA_BUTTONS | MediaSessionCompat. FLAG_HANDLES_TRANSPORT_CONTROLS); mMediaSession.setCallback( new ExampleCallbacks()); 

// Right after audio focus mMediaSession.setActive(true); // On stop mMediaSession.setActive(false); // In onStartCommand() MediaButtonReceiver.handleIntent( mMediaSession, intent); setActive(boolean) setActive(boolean) handleIntent() links media buttons to Callback methods MediaSessionCompat 

PlaybackStateCompat MediaSessionCompat PlaybackStateCompat setState() setActions() setState() 

Lock screen controls Requires an image Set via setMetadata(MediaMetadataCompat) Metadata isn’t just for the lock screen - Android Wear also uses it! 

Important Metadata Fields Bitmap ● METADATA_KEY_ART ● METADATA_KEY_ALBUM_ART Uri ● METADATA_KEY_ART_URI ● METADATA_KEY_ALBUM_ART_URI Also consider METADATA_KEY_USER_RATING Text ● METADATA_KEY_TITLE ● METADATA_KEY_ARTIST ● METADATA_KEY_ALBUM ● METADATA_KEY_ALBUM_ARTIST Long ● METADATA_KEY_DURATION 

Lifecycle of media playback Created Playing Paused Stopped Destroyed MediaPlayer new prepare -> play pause stop release Audio Focus request focus abandon focus NOISY register unregister MediaSession Compat new set flags set callback setActive(true) set metadata set state set state setActive(false) release Lock screen on 5.0+? 

Notifications and media controls NotificationCompat.MediaStyle ●

public static NotificationCompat.Builder from( Context context, MediaSessionCompat mediaSession) { } public static NotificationCompat.Builder from( Context context, MediaSessionCompat mediaSession) { MediaControllerCompat controller = mediaSession.getController(); MediaMetadataCompat mediaMetadata = controller.getMetadata(); MediaDescriptionCompat description = mediaMetadata.getDescription(); } public static NotificationCompat.Builder from( Context context, MediaSessionCompat mediaSession) { MediaControllerCompat controller = mediaSession.getController(); MediaMetadataCompat mediaMetadata = controller.getMetadata(); MediaDescriptionCompat description = mediaMetadata.getDescription(); NotificationCompat.Builder builder = new NotificationCompat.Builder(context); builder .setContentTitle(description.getTitle()) .setContentText(description.getSubtitle()) .setSubText(description.getDescription()) .setLargeIcon(description.getIconBitmap()) .setContentIntent(controller.getSessionActivity()) .setVisibility(NotificationCompat.VISIBILITY_PUBLIC) .setDeleteIntent(getActionIntent(context, KeyEvent.KEYCODE_MEDIA_STOP)); return builder; } 

public static PendingIntent getActionIntent( Context context, int mediaKeyEvent) { Intent intent = new Intent(Intent.ACTION_MEDIA_BUTTON); intent.setPackage(context.getPackageName()); intent.putExtra(Intent.EXTRA_KEY_EVENT, new KeyEvent(KeyEvent.ACTION_DOWN, mediaKeyEvent)); return PendingIntent.getBroadcast(context, mediaKeyEvent, intent, 0); } Full code at gist.github.com/ianhanniballake/47617ec3488e0257325c 

NotificationCompat.Builder builder = MediaStyleHelper.from(this, mediaSession); builder .setSmallIcon(R.drawable.notification_icon) .setColor(ContextCompat.getColor(this, R.color.primaryDark)); builder .addAction(new NotificationCompat.Action( R.drawable.pause, getString(R.string.pause), MediaStyleHelper.getActionIntent(this, KeyEvent.KEYCODE_MEDIA_PLAY_PAUSE))); builder.setStyle(new NotificationCompat.MediaStyle() .setShowActionsInCompactView(0) .setMediaSession(mediaSession.getSessionToken())); 

Lifecycle of media playback Created Playing Paused Stopped Destroyed MediaPlayer new prepare -> play pause stop release Audio Focus request focus abandon focus NOISY register unregister MediaSession Compat new set flags set callback setActive(true) set metadata set state set state setActive(false) release Notification show notification update notification clear notification 

Foreground Services Caveat: always ongoing pre-Lollipop 

Handling ongoing pre-Lollipop builder.setStyle(new NotificationCompat.MediaStyle() .setShowActionsInCompactView(0) .setMediaSession(mediaSession.getSessionToken()) .setShowCancelButton(true) .setCancelButtonIntent(MediaStyleHelper.getActionIntent(context, KeyEvent.KEYCODE_MEDIA_STOP)); 

Lifecycle of media playback Created Playing Paused Stopped Destroyed MediaPlayer new prepare -> play pause stop release Audio Focus request focus abandon focus NOISY register unregister MediaSession Compat new set flags set callback setActive(true) set metadata set state set state setActive(false) release Notification start FG stopFG(false) stopFG(true) 

Service <-> UI 

MediaControllerCompat getMetadata() -> MediaMetadataCompat getPlaybackState() -> PlaybackStateCompat getTransportControls() -> 1:1 with Callback MediaControllerCompat.Callback 

MediaControllerCompat requires a Token 

MediaBrowserService / MediaBrowser API to connect and retrieve a Token New APIs for browsing available media items Required for Android Auto integration Adds browse option on Android Wear notification 

Implementing MediaBrowserService Call setSessionToken() in onCreate() New methods: ● onGetRoot() ● onLoadChildren() ● onLoadItem() See example Universal Android Music Player (UAMP) github.com/googlesamples/android-UniversalMusicPlayer 

Using MediaControllerCompat Bind to Service, build API to retrieve Token ● Pros: ensures Service will be alive and ready while UI is up ● Cons: complicated Static getSessionToken() method in Service, send a local broadcast on change ● Pros: simple ● Cons: no multi-process, still need to start the Service 

Lifecycle of media playback Created Playing Paused Stopped Destroyed MediaPlayer new prepare -> play pause stop release Audio Focus request focus abandon focus NOISY register unregister MediaSession Compat new set flags set callback setActive(true) set metadata set state set state setActive(false) release Notification start FG stopFG(false) stopFG(true) MediaBrowser Service set session token 

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