Media Session Compat not showing Lockscreen controls on Pre-Lollipop

While not strictly required for MediaSession, RemoteControlClient used on API14-19 devices, does require audio focus and it is 100% strongly recommended for all media playback.

Adding lines such as:

AudioManager audioManager = (AudioManager)    getSystemService(Context.AUDIO_SERVICE);int result = audioManager.requestAudioFocus(this,    AudioManager.STREAM_MUSIC, AudioManager.AUDIOFOCUS_GAIN);if (result != AudioManager.AUDIOFOCUS_GAIN) {    return; //Failed to gain audio focus}

Before playing any media should gain audio focus and show controls.

Finally I figured a solution for this. Thanks to @ianhanniballake & @user1549672

1. Add Audio Focus as suggested by @ianhanniballake
2. Add Music Intent BroadcastReceiver can be found if searched on Google & also on Official Android Docs
3. Write the setupMediaSession() given in my question above
4. VERY IMPORTANT Mention the Flags properly
5. Write MediaSessionCallbacks also available above
6. VERY IMPORTANT Update the MediaSession on MediaPlayer#onPause(), MediaPlayer#onStart() & finally when new song is played (also includes next & previous played) mentioned by @user1549672
7. Release the MediaSession object in onDestory()

Well that's all, most of the material (code) is available above. This question took couple of months to solve, finally it's done.

Finally I got an answer to your's and my problem .Issue is you need to specify actions (mMediaSessionCompat.setActions(PlaybackStateCompat.ACTION_PLAY_PAUSE) even while updating mediasession. So your code should now look like

  private void updateMediaSessionMetaData() {     int playState = mPlaying            ? PlaybackStateCompat.STATE_PLAYING            : PlaybackStateCompat.STATE_PAUSED;           mMediaSessionCompat.setMetadata(new MediaMetadataCompat.Builder()                .putString(MediaMetadata.METADATA_KEY_ARTIST, getArtist())                .putString(MediaMetadata.METADATA_KEY_ALBUM, getAlbum())                .putString(MediaMetadata.METADATA_KEY_TITLE, getSongTitle())                .putLong(MediaMetadata.METADATA_KEY_DURATION, duration())                .putLong(MediaMetadata.METADATA_KEY_TRACK_NUMBER, mSongPosn)                .putLong(MediaMetadata.METADATA_KEY_NUM_TRACKS, songs.size())                .putBitmap(MediaMetadata.METADATA_KEY_ALBUM_ART, albumArt)                .build());mMediaSessionCompat.setPlaybackState(new PlaybackStateCompat.Builder()                .setState(playState, position(), 1.0f)                .setActions(PlaybackStateCompat.ACTION_PLAY_PAUSE| PlaybackStateCompat.ACTION_SKIP_TO_NEXT|PlaybackStateCompat.ACTION_SKIP_TO_PREVIOUS).build()); 

UPDATE : Added code for MediaCallback & Receiver

   private final class MediaSessionCallback extends MediaSessionCompat.Callback {    @Override    public void onPlay() {        pausePlayer();    }    @Override    public void onPause() {        pausePlayer();    }    public void onSeekTo(long pos) {        seek(pos);    }    @Override    public void onSkipToNext() {        playNext();    }    @Override    public void onSkipToPrevious() {        playPrev();    }}

Receiver :

 public class MusicIntentReceiver extends BroadcastReceiver {@Overridepublic void onReceive(Context context, Intent intent) {        if (intent.getAction().equals(                android.media.AudioManager.ACTION_AUDIO_BECOMING_NOISY)) {            Intent intent1 = new Intent(MusicService.ACTION_PAUSE);            intent1.setClass(context,                    com.xyz.service.MusicService.class);            // send an intent to our MusicService to telling it to pause the            // audio            context.startService(intent1);        } else if (intent.getAction().equals(Intent.ACTION_MEDIA_BUTTON)) {            KeyEvent keyEvent = (KeyEvent) intent.getExtras().get(                    Intent.EXTRA_KEY_EVENT);            if (keyEvent.getAction() != KeyEvent.ACTION_DOWN)                return;            switch (keyEvent.getKeyCode()) {                case KeyEvent.KEYCODE_HEADSETHOOK:                case KeyEvent.KEYCODE_MEDIA_PLAY_PAUSE:                    Intent intentToggle = new Intent(                            MusicService.ACTION_TOGGLE_PLAYBACK);                    intentToggle.setClass(context,                            com.xyz.service.MusicService.class);                    context.startService(intentToggle);                    break;                case KeyEvent.KEYCODE_MEDIA_PLAY:                    Intent intentPlay = new Intent(MusicService.ACTION_PLAY);                    intentPlay.setClass(context,                            com.xyz.service.MusicService.class);                    context.startService(intentPlay);                    break;                case KeyEvent.KEYCODE_MEDIA_PAUSE:                    Intent intentPause = new Intent(MusicService.ACTION_PAUSE);                    intentPause.setClass(context,                            com.xyz.service.MusicService.class);                    context.startService(intentPause);                    break;                case KeyEvent.KEYCODE_MEDIA_NEXT:                    Intent intentNext = new Intent(MusicService.ACTION_NEXT);                    intentNext.setClass(context,                            com.xyz.service.MusicService.class);                    context.startService(intentNext);                    break;                case KeyEvent.KEYCODE_MEDIA_PREVIOUS:                    Intent intentPrev = new Intent(MusicService.ACTION_PREV);                    intentPrev.setClass(context,                            com.xyz.service.MusicService.class);                    context.startService(intentPrev);                    break;                default:                    break;            }        }    }}