Safer thread synchronization for song timeline

src/org/kreed/vanilla/PlaybackService.java

@@ -296,6 +296,7 @@ public class PlaybackService extends Service implements Runnable, MediaPlayer.On
 
 	private int[] mSongs;
 	private ArrayList<Song> mSongTimeline;
+	private Object mSongTimelineLock = new Object();
 	private int mCurrentSong = 0;
 	private int mQueuePos = 0;
 	private int mState = STATE_NORMAL;
@@ -527,7 +528,9 @@ public class PlaybackService extends Service implements Runnable, MediaPlayer.On
 		if (song == null)
 			return;
 
+		synchronized (mSongTimelineLock) {
 			mCurrentSong += delta;
+		}
 
 		try {
 			mMediaPlayer.reset();
@@ -545,11 +548,13 @@ public class PlaybackService extends Service implements Runnable, MediaPlayer.On
 
 		getSong(+2);
 
+		synchronized (mSongTimelineLock) {
 			while (mCurrentSong > 15) {
 				mSongTimeline.remove(0);
 				--mCurrentSong;
 			}
 		}
+	}
 
 	public void onCompletion(MediaPlayer player)
 	{
@@ -572,8 +577,9 @@ public class PlaybackService extends Service implements Runnable, MediaPlayer.On
 		return new Song(mSongs[mRandom.nextInt(mSongs.length)]);
 	}
 
-	private synchronized Song getSong(int delta)
+	private Song getSong(int delta)
 	{
+		synchronized (mSongTimelineLock) {
 			if (mSongTimeline == null)
 				return null;
 	
@@ -594,6 +600,7 @@ public class PlaybackService extends Service implements Runnable, MediaPlayer.On
 	
 			return mSongTimeline.get(pos);
 		}
+	}
 
 	private void updateWidgets()
 	{
@@ -635,12 +642,14 @@ public class PlaybackService extends Service implements Runnable, MediaPlayer.On
 					String text = getResources().getString(R.string.enqueued, song.title);
 					Toast.makeText(ContextApplication.getContext(), text, Toast.LENGTH_SHORT).show();
 
+					synchronized (mSongTimelineLock) {
 						int i = mCurrentSong + 1 + mQueuePos++;
 						if (i < mSongTimeline.size())
 							mSongTimeline.set(i, song);
 						else
 							mSongTimeline.add(song);
 					}
+				}
 				break;
 			case TRACK_CHANGED:
 				setCurrentSong(+1);