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Displaying a Now Playing Card

TV apps may allow users to play music or other media in the background while using other applications. If your app allows this type of use, it must must provide a means for the user to return to the app to pause the music or switch to a new song. The Android framework enables TV apps to do this by displaying a Now Playing card on the home screen in the recommendations row.

The Now Playing card is a system artifact that displays on the home screen in the recommendations row for an active media session. It includes the media metadata such as the album art, title, and app icon. When the user selects it, the system opens the the app that owns the session.

This lesson shows how to use the MediaSession class to implement the Now Playing card.

Start a Media Session

A playback app can run as an activity or as a service. The service is required for background playback because it can continue to play media even after the activity that launched it has been destroyed. For this discussion, the media playback app is assumed to be running in a MediaBrowserService.

In your service's onCreate() method, create a new MediaSession, set the callback and flags appropriate to a media app, and set the session token for the MediaBrowserService.

mSession = new MediaSession(this, "MusicService");
mSession.setCallback(new MediaSessionCallback());
mSession.setFlags(MediaSession.FLAG_HANDLES_MEDIA_BUTTONS |
        MediaSession.FLAG_HANDLES_TRANSPORT_CONTROLS);
// for the MediaBrowserService
setSessionToken(mSession.getSessionToken());

Note: The Now Playing card will display only for a media session with the FLAG_HANDLES_TRANSPORT_CONTROLS flag set.

Display a Now Playing Card

The Now Playing card shows up after setActive(true) is called, if the session is the highest priority session in the system. Also, note that your app must request the audio focus, as described in Managing Audio Focus.

private void handlePlayRequest() {
    tryToGetAudioFocus();
    if (!mSession.isActive()) {
        mSession.setActive(true);
    }
...

The card is removed from the home screen when setActive(false) is called or if another app initiates media playback. You may want to remove the card from the home screen some time after playback is paused, depending on how long you want to keep the card up, usually 5 to 30 minutes.

Update the Playback State

As with any media app, update the playback state in the MediaSession so that the card can display the current metadata, as shown in the following example:

private void updatePlaybackState() {
    long position = PlaybackState.PLAYBACK_POSITION_UNKNOWN;
    if (mMediaPlayer != null && mMediaPlayer.isPlaying()) {
        position = mMediaPlayer.getCurrentPosition();
    }
    PlaybackState.Builder stateBuilder = new PlaybackState.Builder()
            .setActions(getAvailableActions());
    stateBuilder.setState(mState, position, 1.0f);
    mSession.setPlaybackState(stateBuilder.build());
}
private long getAvailableActions() {
    long actions = PlaybackState.ACTION_PLAY |
            PlaybackState.ACTION_PLAY_FROM_MEDIA_ID |
            PlaybackState.ACTION_PLAY_FROM_SEARCH;
    if (mPlayingQueue == null || mPlayingQueue.isEmpty()) {
        return actions;
    }
    if (mState == PlaybackState.STATE_PLAYING) {
        actions |= PlaybackState.ACTION_PAUSE;
    }
    if (mCurrentIndexOnQueue > 0) {
        actions |= PlaybackState.ACTION_SKIP_TO_PREVIOUS;
    }
    if (mCurrentIndexOnQueue < mPlayingQueue.size() - 1) {
        actions |= PlaybackState.ACTION_SKIP_TO_NEXT;
    }
    return actions;
}

Display the Media Metadata

For the track currently playing, set the MediaMetadata with the setMetadata() method. This method of the media session object lets you provide information to the Now Playing card about the track such as the title, subtitle, and various icons. The following example assumes your track's data is stored in a custom data class, MediaData.

private void updateMetadata(MediaData myData) {
    MediaMetadata.Builder metadataBuilder = new MediaMetadata.Builder();
    // To provide most control over how an item is displayed set the
    // display fields in the metadata
    metadataBuilder.putString(MediaMetadata.METADATA_KEY_DISPLAY_TITLE,
            myData.displayTitle);
    metadataBuilder.putString(MediaMetadata.METADATA_KEY_DISPLAY_SUBTITLE,
            myData.displaySubtitle);
    metadataBuilder.putString(MediaMetadata.METADATA_KEY_DISPLAY_ICON_URI,
            myData.artUri);
    // And at minimum the title and artist for legacy support
    metadataBuilder.putString(MediaMetadata.METADATA_KEY_TITLE,
            myData.title);
    metadataBuilder.putString(MediaMetadata.METADATA_KEY_ARTIST,
            myData.artist);
    // A small bitmap for the artwork is also recommended
    metadataBuilder.putString(MediaMetadata.METADATA_KEY_ART,
            myData.artBitmap);
    // Add any other fields you have for your data as well
    mSession.setMetadata(metadataBuilder.build());
}

Respond to User Action

When the user selects the Now Playing card, the system opens the app that owns the session. If your app provides a PendingIntent to pass to setSessionActivity(), the system launches the activity you specify, as demonstrated below. If not, the default system intent opens. The activity you specify must provide playback controls that allow users to pause or stop playback.

Intent intent = new Intent(mContext, MyActivity.class);
    PendingIntent pi = PendingIntent.getActivity(context, 99 /*request code*/,
            intent, PendingIntent.FLAG_UPDATE_CURRENT);
    mSession.setSessionActivity(pi);