xref: /aosp_15_r20/development/samples/browseable/MediaBrowserService/src/com.example.android.mediabrowserservice/MusicService.java (revision 90c8c64db3049935a07c6143d7fd006e26f8ecca)

 /*
 * Copyright (C) 2014 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.example.android.mediabrowserservice;

 import android.app.PendingIntent;
 import android.content.Context;
 import android.content.Intent;
 import android.graphics.Bitmap;
 import android.media.MediaDescription;
 import android.media.MediaMetadata;
 import android.media.browse.MediaBrowser.MediaItem;
 import android.media.session.MediaSession;
 import android.media.session.PlaybackState;
 import android.net.Uri;
 import android.os.Bundle;
 import android.os.Handler;
 import android.os.Message;
 import android.os.SystemClock;
 import android.service.media.MediaBrowserService;
 import android.text.TextUtils;

 import com.example.android.mediabrowserservice.model.MusicProvider;
 import com.example.android.mediabrowserservice.utils.CarHelper;
 import com.example.android.mediabrowserservice.utils.LogHelper;
 import com.example.android.mediabrowserservice.utils.MediaIDHelper;
 import com.example.android.mediabrowserservice.utils.QueueHelper;

 import java.lang.ref.WeakReference;
 import java.util.ArrayList;
 import java.util.Collections;
 import java.util.List;

 import static com.example.android.mediabrowserservice.utils.MediaIDHelper.MEDIA_ID_MUSICS_BY_GENRE;
 import static com.example.android.mediabrowserservice.utils.MediaIDHelper.MEDIA_ID_ROOT;
 import static com.example.android.mediabrowserservice.utils.MediaIDHelper.createBrowseCategoryMediaID;

 /**
  * This class provides a MediaBrowser through a service. It exposes the media library to a browsing
  * client, through the onGetRoot and onLoadChildren methods. It also creates a MediaSession and
  * exposes it through its MediaSession.Token, which allows the client to create a MediaController
  * that connects to and send control commands to the MediaSession remotely. This is useful for
  * user interfaces that need to interact with your media session, like Android Auto. You can
  * (should) also use the same service from your app's UI, which gives a seamless playback
  * experience to the user.
  *
  * To implement a MediaBrowserService, you need to:
  *
  * <ul>
  *
  * <li> Extend {@link android.service.media.MediaBrowserService}, implementing the media browsing
  *      related methods {@link android.service.media.MediaBrowserService#onGetRoot} and
  *      {@link android.service.media.MediaBrowserService#onLoadChildren};
  * <li> In onCreate, start a new {@link android.media.session.MediaSession} and notify its parent
  *      with the session's token {@link android.service.media.MediaBrowserService#setSessionToken};
  *
  * <li> Set a callback on the
  *      {@link android.media.session.MediaSession#setCallback(android.media.session.MediaSession.Callback)}.
  *      The callback will receive all the user's actions, like play, pause, etc;
  *
  * <li> Handle all the actual music playing using any method your app prefers (for example,
  *      {@link android.media.MediaPlayer})
  *
  * <li> Update playbackState, "now playing" metadata and queue, using MediaSession proper methods
  *      {@link android.media.session.MediaSession#setPlaybackState(android.media.session.PlaybackState)}
  *      {@link android.media.session.MediaSession#setMetadata(android.media.MediaMetadata)} and
  *      {@link android.media.session.MediaSession#setQueue(java.util.List)})
  *
  * <li> Declare and export the service in AndroidManifest with an intent receiver for the action
  *      android.media.browse.MediaBrowserService
  *
  * </ul>
  *
  * To make your app compatible with Android Auto, you also need to:
  *
  * <ul>
  *
  * <li> Declare a meta-data tag in AndroidManifest.xml linking to a xml resource
  *      with a &lt;automotiveApp&gt; root element. For a media app, this must include
  *      an &lt;uses name="media"/&gt; element as a child.
  *      For example, in AndroidManifest.xml:
  *          &lt;meta-data android:name="com.google.android.gms.car.application"
  *              android:resource="@xml/automotive_app_desc"/&gt;
  *      And in res/values/automotive_app_desc.xml:
  *          &lt;automotiveApp&gt;
  *              &lt;uses name="media"/&gt;
  *          &lt;/automotiveApp&gt;
  *
  * </ul>

  * @see <a href="README.md">README.md</a> for more details.
  *
  */

 public class MusicService extends MediaBrowserService implements Playback.Callback {

     // The action of the incoming Intent indicating that it contains a command
     // to be executed (see {@link #onStartCommand})
     public static final String ACTION_CMD = "com.example.android.mediabrowserservice.ACTION_CMD";
     // The key in the extras of the incoming Intent indicating the command that
     // should be executed (see {@link #onStartCommand})
     public static final String CMD_NAME = "CMD_NAME";
     // A value of a CMD_NAME key in the extras of the incoming Intent that
     // indicates that the music playback should be paused (see {@link #onStartCommand})
     public static final String CMD_PAUSE = "CMD_PAUSE";

     private static final String TAG = LogHelper.makeLogTag(MusicService.class);
     // Action to thumbs up a media item
     private static final String CUSTOM_ACTION_THUMBS_UP =
         "com.example.android.mediabrowserservice.THUMBS_UP";
     // Delay stopSelf by using a handler.
     private static final int STOP_DELAY = 30000;

     // Music catalog manager
     private MusicProvider mMusicProvider;
     private MediaSession mSession;
     // "Now playing" queue:
     private List<MediaSession.QueueItem> mPlayingQueue;
     private int mCurrentIndexOnQueue;
     private MediaNotificationManager mMediaNotificationManager;
     // Indicates whether the service was started.
     private boolean mServiceStarted;
     private DelayedStopHandler mDelayedStopHandler = new DelayedStopHandler(this);
     private Playback mPlayback;
     private PackageValidator mPackageValidator;

     /*
      * (non-Javadoc)
      * @see android.app.Service#onCreate()
      */
     @Override
     public void onCreate() {
         super.onCreate();
         LogHelper.d(TAG, "onCreate");

         mPlayingQueue = new ArrayList<>();
         mMusicProvider = new MusicProvider();
         mPackageValidator = new PackageValidator(this);

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

         mPlayback = new Playback(this, mMusicProvider);
         mPlayback.setState(PlaybackState.STATE_NONE);
         mPlayback.setCallback(this);
         mPlayback.start();

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

         Bundle extras = new Bundle();
         CarHelper.setSlotReservationFlags(extras, true, true, true);
         mSession.setExtras(extras);

         updatePlaybackState(null);

         mMediaNotificationManager = new MediaNotificationManager(this);
     }

     /**
      * (non-Javadoc)
      * @see android.app.Service#onStartCommand(android.content.Intent, int, int)
      */
     @Override
     public int onStartCommand(Intent startIntent, int flags, int startId) {
         if (startIntent != null) {
             String action = startIntent.getAction();
             String command = startIntent.getStringExtra(CMD_NAME);
             if (ACTION_CMD.equals(action)) {
                 if (CMD_PAUSE.equals(command)) {
                     if (mPlayback != null && mPlayback.isPlaying()) {
                         handlePauseRequest();
                     }
                 }
             }
         }
         return START_STICKY;
     }

     /**
      * (non-Javadoc)
      * @see android.app.Service#onDestroy()
      */
     @Override
     public void onDestroy() {
         LogHelper.d(TAG, "onDestroy");
         // Service is being killed, so make sure we release our resources
         handleStopRequest(null);

         mDelayedStopHandler.removeCallbacksAndMessages(null);
         // Always release the MediaSession to clean up resources
         // and notify associated MediaController(s).
         mSession.release();
     }

     @Override
     public BrowserRoot onGetRoot(String clientPackageName, int clientUid, Bundle rootHints) {
         LogHelper.d(TAG, "OnGetRoot: clientPackageName=" + clientPackageName,
                 "; clientUid=" + clientUid + " ; rootHints=", rootHints);
         // To ensure you are not allowing any arbitrary app to browse your app's contents, you
         // need to check the origin:
         if (!mPackageValidator.isCallerAllowed(this, clientPackageName, clientUid)) {
             // If the request comes from an untrusted package, return null. No further calls will
             // be made to other media browsing methods.
             LogHelper.w(TAG, "OnGetRoot: IGNORING request from untrusted package "
                     + clientPackageName);
             return null;
         }
         //noinspection StatementWithEmptyBody
         if (CarHelper.isValidCarPackage(clientPackageName)) {
             // Optional: if your app needs to adapt ads, music library or anything else that
             // needs to run differently when connected to the car, this is where you should handle
             // it.
         }
         return new BrowserRoot(MEDIA_ID_ROOT, null);
     }

     @Override
     public void onLoadChildren(final String parentMediaId, final Result<List<MediaItem>> result) {
         if (!mMusicProvider.isInitialized()) {
             // Use result.detach to allow calling result.sendResult from another thread:
             result.detach();

             mMusicProvider.retrieveMediaAsync(new MusicProvider.Callback() {
                 @Override
                 public void onMusicCatalogReady(boolean success) {
                     if (success) {
                         loadChildrenImpl(parentMediaId, result);
                     } else {
                         updatePlaybackState(getString(R.string.error_no_metadata));
                         result.sendResult(Collections.<MediaItem>emptyList());
                     }
                 }
             });

         } else {
             // If our music catalog is already loaded/cached, load them into result immediately
             loadChildrenImpl(parentMediaId, result);
         }
     }

     /**
      * Actual implementation of onLoadChildren that assumes that MusicProvider is already
      * initialized.
      */
     private void loadChildrenImpl(final String parentMediaId,
                                   final Result<List<MediaItem>> result) {
         LogHelper.d(TAG, "OnLoadChildren: parentMediaId=", parentMediaId);

         List<MediaItem> mediaItems = new ArrayList<>();

         if (MEDIA_ID_ROOT.equals(parentMediaId)) {
             LogHelper.d(TAG, "OnLoadChildren.ROOT");
             mediaItems.add(new MediaItem(
                     new MediaDescription.Builder()
                         .setMediaId(MEDIA_ID_MUSICS_BY_GENRE)
                         .setTitle(getString(R.string.browse_genres))
                         .setIconUri(Uri.parse("android.resource://" +
                             "com.example.android.mediabrowserservice/drawable/ic_by_genre"))
                         .setSubtitle(getString(R.string.browse_genre_subtitle))
                         .build(), MediaItem.FLAG_BROWSABLE
             ));

         } else if (MEDIA_ID_MUSICS_BY_GENRE.equals(parentMediaId)) {
             LogHelper.d(TAG, "OnLoadChildren.GENRES");
             for (String genre : mMusicProvider.getGenres()) {
                 MediaItem item = new MediaItem(
                     new MediaDescription.Builder()
                         .setMediaId(createBrowseCategoryMediaID(MEDIA_ID_MUSICS_BY_GENRE, genre))
                         .setTitle(genre)
                         .setSubtitle(getString(R.string.browse_musics_by_genre_subtitle, genre))
                         .build(), MediaItem.FLAG_BROWSABLE
                 );
                 mediaItems.add(item);
             }

         } else if (parentMediaId.startsWith(MEDIA_ID_MUSICS_BY_GENRE)) {
             String genre = MediaIDHelper.getHierarchy(parentMediaId)[1];
             LogHelper.d(TAG, "OnLoadChildren.SONGS_BY_GENRE  genre=", genre);
             for (MediaMetadata track : mMusicProvider.getMusicsByGenre(genre)) {
                 // Since mediaMetadata fields are immutable, we need to create a copy, so we
                 // can set a hierarchy-aware mediaID. We will need to know the media hierarchy
                 // when we get a onPlayFromMusicID call, so we can create the proper queue based
                 // on where the music was selected from (by artist, by genre, random, etc)
                 String hierarchyAwareMediaID = MediaIDHelper.createMediaID(
                         track.getDescription().getMediaId(), MEDIA_ID_MUSICS_BY_GENRE, genre);
                 MediaMetadata trackCopy = new MediaMetadata.Builder(track)
                         .putString(MediaMetadata.METADATA_KEY_MEDIA_ID, hierarchyAwareMediaID)
                         .build();
                 MediaItem bItem = new MediaItem(
                         trackCopy.getDescription(), MediaItem.FLAG_PLAYABLE);
                 mediaItems.add(bItem);
             }
         } else {
             LogHelper.w(TAG, "Skipping unmatched parentMediaId: ", parentMediaId);
         }
         LogHelper.d(TAG, "OnLoadChildren sending ", mediaItems.size(),
                 " results for ", parentMediaId);
         result.sendResult(mediaItems);
     }

     private final class MediaSessionCallback extends MediaSession.Callback {
         @Override
         public void onPlay() {
             LogHelper.d(TAG, "play");

             if (mPlayingQueue == null || mPlayingQueue.isEmpty()) {
                 mPlayingQueue = QueueHelper.getRandomQueue(mMusicProvider);
                 mSession.setQueue(mPlayingQueue);
                 mSession.setQueueTitle(getString(R.string.random_queue_title));
                 // start playing from the beginning of the queue
                 mCurrentIndexOnQueue = 0;
             }

             if (mPlayingQueue != null && !mPlayingQueue.isEmpty()) {
                 handlePlayRequest();
             }
         }

         @Override
         public void onSkipToQueueItem(long queueId) {
             LogHelper.d(TAG, "OnSkipToQueueItem:" + queueId);

             if (mPlayingQueue != null && !mPlayingQueue.isEmpty()) {
                 // set the current index on queue from the music Id:
                 mCurrentIndexOnQueue = QueueHelper.getMusicIndexOnQueue(mPlayingQueue, queueId);
                 // play the music
                 handlePlayRequest();
             }
         }

         @Override
         public void onSeekTo(long position) {
             LogHelper.d(TAG, "onSeekTo:", position);
             mPlayback.seekTo((int) position);
         }

         @Override
         public void onPlayFromMediaId(String mediaId, Bundle extras) {
             LogHelper.d(TAG, "playFromMediaId mediaId:", mediaId, "  extras=", extras);

             // The mediaId used here is not the unique musicId. This one comes from the
             // MediaBrowser, and is actually a "hierarchy-aware mediaID": a concatenation of
             // the hierarchy in MediaBrowser and the actual unique musicID. This is necessary
             // so we can build the correct playing queue, based on where the track was
             // selected from.
             mPlayingQueue = QueueHelper.getPlayingQueue(mediaId, mMusicProvider);
             mSession.setQueue(mPlayingQueue);
             String queueTitle = getString(R.string.browse_musics_by_genre_subtitle,
                     MediaIDHelper.extractBrowseCategoryValueFromMediaID(mediaId));
             mSession.setQueueTitle(queueTitle);

             if (mPlayingQueue != null && !mPlayingQueue.isEmpty()) {
                 // set the current index on queue from the media Id:
                 mCurrentIndexOnQueue = QueueHelper.getMusicIndexOnQueue(mPlayingQueue, mediaId);

                 if (mCurrentIndexOnQueue < 0) {
                     LogHelper.e(TAG, "playFromMediaId: media ID ", mediaId,
                             " could not be found on queue. Ignoring.");
                 } else {
                     // play the music
                     handlePlayRequest();
                 }
             }
         }

         @Override
         public void onPause() {
             LogHelper.d(TAG, "pause. current state=" + mPlayback.getState());
             handlePauseRequest();
         }

         @Override
         public void onStop() {
             LogHelper.d(TAG, "stop. current state=" + mPlayback.getState());
             handleStopRequest(null);
         }

         @Override
         public void onSkipToNext() {
             LogHelper.d(TAG, "skipToNext");
             mCurrentIndexOnQueue++;
             if (mPlayingQueue != null && mCurrentIndexOnQueue >= mPlayingQueue.size()) {
                 // This sample's behavior: skipping to next when in last song returns to the
                 // first song.
                 mCurrentIndexOnQueue = 0;
             }
             if (QueueHelper.isIndexPlayable(mCurrentIndexOnQueue, mPlayingQueue)) {
                 handlePlayRequest();
             } else {
                 LogHelper.e(TAG, "skipToNext: cannot skip to next. next Index=" +
                         mCurrentIndexOnQueue + " queue length=" +
                         (mPlayingQueue == null ? "null" : mPlayingQueue.size()));
                 handleStopRequest("Cannot skip");
             }
         }

         @Override
         public void onSkipToPrevious() {
             LogHelper.d(TAG, "skipToPrevious");
             mCurrentIndexOnQueue--;
             if (mPlayingQueue != null && mCurrentIndexOnQueue < 0) {
                 // This sample's behavior: skipping to previous when in first song restarts the
                 // first song.
                 mCurrentIndexOnQueue = 0;
             }
             if (QueueHelper.isIndexPlayable(mCurrentIndexOnQueue, mPlayingQueue)) {
                 handlePlayRequest();
             } else {
                 LogHelper.e(TAG, "skipToPrevious: cannot skip to previous. previous Index=" +
                         mCurrentIndexOnQueue + " queue length=" +
                         (mPlayingQueue == null ? "null" : mPlayingQueue.size()));
                 handleStopRequest("Cannot skip");
             }
         }

         @Override
         public void onCustomAction(String action, Bundle extras) {
             if (CUSTOM_ACTION_THUMBS_UP.equals(action)) {
                 LogHelper.i(TAG, "onCustomAction: favorite for current track");
                 MediaMetadata track = getCurrentPlayingMusic();
                 if (track != null) {
                     String musicId = track.getString(MediaMetadata.METADATA_KEY_MEDIA_ID);
                     mMusicProvider.setFavorite(musicId, !mMusicProvider.isFavorite(musicId));
                 }
                 // playback state needs to be updated because the "Favorite" icon on the
                 // custom action will change to reflect the new favorite state.
                 updatePlaybackState(null);
             } else {
                 LogHelper.e(TAG, "Unsupported action: ", action);
             }
         }

         @Override
         public void onPlayFromSearch(String query, Bundle extras) {
             LogHelper.d(TAG, "playFromSearch  query=", query);

             if (TextUtils.isEmpty(query)) {
                 // A generic search like "Play music" sends an empty query
                 // and it's expected that we start playing something. What will be played depends
                 // on the app: favorite playlist, "I'm feeling lucky", most recent, etc.
                 mPlayingQueue = QueueHelper.getRandomQueue(mMusicProvider);
             } else {
                 mPlayingQueue = QueueHelper.getPlayingQueueFromSearch(query, mMusicProvider);
             }

             LogHelper.d(TAG, "playFromSearch  playqueue.length=" + mPlayingQueue.size());
             mSession.setQueue(mPlayingQueue);

             if (mPlayingQueue != null && !mPlayingQueue.isEmpty()) {
                 // immediately start playing from the beginning of the search results
                 mCurrentIndexOnQueue = 0;

                 handlePlayRequest();
             } else {
                 // if nothing was found, we need to warn the user and stop playing
                 handleStopRequest(getString(R.string.no_search_results));
             }
         }
     }

     /**
      * Handle a request to play music
      */
     private void handlePlayRequest() {
         LogHelper.d(TAG, "handlePlayRequest: mState=" + mPlayback.getState());

         mDelayedStopHandler.removeCallbacksAndMessages(null);
         if (!mServiceStarted) {
             LogHelper.v(TAG, "Starting service");
             // The MusicService needs to keep running even after the calling MediaBrowser
             // is disconnected. Call startService(Intent) and then stopSelf(..) when we no longer
             // need to play media.
             startService(new Intent(getApplicationContext(), MusicService.class));
             mServiceStarted = true;
         }

         if (!mSession.isActive()) {
             mSession.setActive(true);
         }

         if (QueueHelper.isIndexPlayable(mCurrentIndexOnQueue, mPlayingQueue)) {
             updateMetadata();
             mPlayback.play(mPlayingQueue.get(mCurrentIndexOnQueue));
         }
     }

     /**
      * Handle a request to pause music
      */
     private void handlePauseRequest() {
         LogHelper.d(TAG, "handlePauseRequest: mState=" + mPlayback.getState());
         mPlayback.pause();
         // reset the delayed stop handler.
         mDelayedStopHandler.removeCallbacksAndMessages(null);
         mDelayedStopHandler.sendEmptyMessageDelayed(0, STOP_DELAY);
     }

     /**
      * Handle a request to stop music
      */
     private void handleStopRequest(String withError) {
         LogHelper.d(TAG, "handleStopRequest: mState=" + mPlayback.getState() + " error=", withError);
         mPlayback.stop(true);
         // reset the delayed stop handler.
         mDelayedStopHandler.removeCallbacksAndMessages(null);
         mDelayedStopHandler.sendEmptyMessageDelayed(0, STOP_DELAY);

         updatePlaybackState(withError);

         // service is no longer necessary. Will be started again if needed.
         stopSelf();
         mServiceStarted = false;
     }

     private void updateMetadata() {
         if (!QueueHelper.isIndexPlayable(mCurrentIndexOnQueue, mPlayingQueue)) {
             LogHelper.e(TAG, "Can't retrieve current metadata.");
             updatePlaybackState(getResources().getString(R.string.error_no_metadata));
             return;
         }
         MediaSession.QueueItem queueItem = mPlayingQueue.get(mCurrentIndexOnQueue);
         String musicId = MediaIDHelper.extractMusicIDFromMediaID(
                 queueItem.getDescription().getMediaId());
         MediaMetadata track = mMusicProvider.getMusic(musicId);
         final String trackId = track.getString(MediaMetadata.METADATA_KEY_MEDIA_ID);
         if (!musicId.equals(trackId)) {
             IllegalStateException e = new IllegalStateException("track ID should match musicId.");
             LogHelper.e(TAG, "track ID should match musicId.",
                 " musicId=", musicId, " trackId=", trackId,
                 " mediaId from queueItem=", queueItem.getDescription().getMediaId(),
                 " title from queueItem=", queueItem.getDescription().getTitle(),
                 " mediaId from track=", track.getDescription().getMediaId(),
                 " title from track=", track.getDescription().getTitle(),
                 " source.hashcode from track=", track.getString(
                     MusicProvider.CUSTOM_METADATA_TRACK_SOURCE).hashCode(),
                 e);
             throw e;
         }
         LogHelper.d(TAG, "Updating metadata for MusicID= " + musicId);
         mSession.setMetadata(track);

         // Set the proper album artwork on the media session, so it can be shown in the
         // locked screen and in other places.
         if (track.getDescription().getIconBitmap() == null &&
                 track.getDescription().getIconUri() != null) {
             String albumUri = track.getDescription().getIconUri().toString();
             AlbumArtCache.getInstance().fetch(albumUri, new AlbumArtCache.FetchListener() {
                 @Override
                 public void onFetched(String artUrl, Bitmap bitmap, Bitmap icon) {
                     MediaSession.QueueItem queueItem = mPlayingQueue.get(mCurrentIndexOnQueue);
                     MediaMetadata track = mMusicProvider.getMusic(trackId);
                     track = new MediaMetadata.Builder(track)

                         // set high resolution bitmap in METADATA_KEY_ALBUM_ART. This is used, for
                         // example, on the lockscreen background when the media session is active.
                         .putBitmap(MediaMetadata.METADATA_KEY_ALBUM_ART, bitmap)

                         // set small version of the album art in the DISPLAY_ICON. This is used on
                         // the MediaDescription and thus it should be small to be serialized if
                         // necessary..
                         .putBitmap(MediaMetadata.METADATA_KEY_DISPLAY_ICON, icon)

                         .build();

                     mMusicProvider.updateMusic(trackId, track);

                     // If we are still playing the same music
                     String currentPlayingId = MediaIDHelper.extractMusicIDFromMediaID(
                         queueItem.getDescription().getMediaId());
                     if (trackId.equals(currentPlayingId)) {
                         mSession.setMetadata(track);
                     }
                 }
             });
         }
     }

     /**
      * Update the current media player state, optionally showing an error message.
      *
      * @param error if not null, error message to present to the user.
      */
     private void updatePlaybackState(String error) {
         LogHelper.d(TAG, "updatePlaybackState, playback state=" + mPlayback.getState());
         long position = PlaybackState.PLAYBACK_POSITION_UNKNOWN;
         if (mPlayback != null && mPlayback.isConnected()) {
             position = mPlayback.getCurrentStreamPosition();
         }

         PlaybackState.Builder stateBuilder = new PlaybackState.Builder()
                 .setActions(getAvailableActions());

         setCustomAction(stateBuilder);
         int state = mPlayback.getState();

         // If there is an error message, send it to the playback state:
         if (error != null) {
             // Error states are really only supposed to be used for errors that cause playback to
             // stop unexpectedly and persist until the user takes action to fix it.
             stateBuilder.setErrorMessage(error);
             state = PlaybackState.STATE_ERROR;
         }
         stateBuilder.setState(state, position, 1.0f, SystemClock.elapsedRealtime());

         // Set the activeQueueItemId if the current index is valid.
         if (QueueHelper.isIndexPlayable(mCurrentIndexOnQueue, mPlayingQueue)) {
             MediaSession.QueueItem item = mPlayingQueue.get(mCurrentIndexOnQueue);
             stateBuilder.setActiveQueueItemId(item.getQueueId());
         }

         mSession.setPlaybackState(stateBuilder.build());

         if (state == PlaybackState.STATE_PLAYING || state == PlaybackState.STATE_PAUSED) {
             mMediaNotificationManager.startNotification();
         }
     }

     private void setCustomAction(PlaybackState.Builder stateBuilder) {
         MediaMetadata currentMusic = getCurrentPlayingMusic();
         if (currentMusic != null) {
             // Set appropriate "Favorite" icon on Custom action:
             String musicId = currentMusic.getString(MediaMetadata.METADATA_KEY_MEDIA_ID);
             int favoriteIcon = R.drawable.ic_star_off;
             if (mMusicProvider.isFavorite(musicId)) {
                 favoriteIcon = R.drawable.ic_star_on;
             }
             LogHelper.d(TAG, "updatePlaybackState, setting Favorite custom action of music ",
                     musicId, " current favorite=", mMusicProvider.isFavorite(musicId));
             stateBuilder.addCustomAction(CUSTOM_ACTION_THUMBS_UP, getString(R.string.favorite),
                 favoriteIcon);
         }
     }

     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 (mPlayback.isPlaying()) {
             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;
     }

     private MediaMetadata getCurrentPlayingMusic() {
         if (QueueHelper.isIndexPlayable(mCurrentIndexOnQueue, mPlayingQueue)) {
             MediaSession.QueueItem item = mPlayingQueue.get(mCurrentIndexOnQueue);
             if (item != null) {
                 LogHelper.d(TAG, "getCurrentPlayingMusic for musicId=",
                         item.getDescription().getMediaId());
                 return mMusicProvider.getMusic(
                         MediaIDHelper.extractMusicIDFromMediaID(item.getDescription().getMediaId()));
             }
         }
         return null;
     }

     /**
      * Implementation of the Playback.Callback interface
      */
     @Override
     public void onCompletion() {
         // The media player finished playing the current song, so we go ahead
         // and start the next.
         if (mPlayingQueue != null && !mPlayingQueue.isEmpty()) {
             // In this sample, we restart the playing queue when it gets to the end:
             mCurrentIndexOnQueue++;
             if (mCurrentIndexOnQueue >= mPlayingQueue.size()) {
                 mCurrentIndexOnQueue = 0;
             }
             handlePlayRequest();
         } else {
             // If there is nothing to play, we stop and release the resources:
             handleStopRequest(null);
         }
     }

     @Override
     public void onPlaybackStatusChanged(int state) {
         updatePlaybackState(null);
     }

     @Override
     public void onError(String error) {
         updatePlaybackState(error);
     }

     /**
      * A simple handler that stops the service if playback is not active (playing)
      */
     private static class DelayedStopHandler extends Handler {
         private final WeakReference<MusicService> mWeakReference;

         private DelayedStopHandler(MusicService service) {
             mWeakReference = new WeakReference<>(service);
         }

         @Override
         public void handleMessage(Message msg) {
             MusicService service = mWeakReference.get();
             if (service != null && service.mPlayback != null) {
                 if (service.mPlayback.isPlaying()) {
                     LogHelper.d(TAG, "Ignoring delayed stop since the media player is in use.");
                     return;
                 }
                 LogHelper.d(TAG, "Stopping service with delay handler.");
                 service.stopSelf();
                 service.mServiceStarted = false;
             }
         }
     }
 }