Minimal MediaSessionCompat needed to get RemoteControlClient to appear

PlayerService.java

package com.example.remotecontrolclient;

import android.app.Service;
import android.content.ComponentName;
import android.content.Context;
import android.content.Intent;
import android.graphics.BitmapFactory;
import android.media.AudioManager;
import android.os.IBinder;
import android.support.v4.media.MediaMetadataCompat;
import android.support.v4.media.session.MediaSessionCompat;
import android.support.v4.media.session.PlaybackStateCompat;

public class PlayerService extends Service {
    private MediaSessionCompat mediaSession;

    @Override
    public void onCreate() {
        super.onCreate();
        ComponentName receiver = new ComponentName(getPackageName(), RemoteReceiver.class.getName());
        mediaSession = new MediaSessionCompat(this, "PlayerService", receiver, null);
        mediaSession.setFlags(MediaSessionCompat.FLAG_HANDLES_MEDIA_BUTTONS |
                MediaSessionCompat.FLAG_HANDLES_TRANSPORT_CONTROLS);
        mediaSession.setPlaybackState(new PlaybackStateCompat.Builder()
                .setState(PlaybackStateCompat.STATE_PAUSED, 0, 0)
                .setActions(PlaybackStateCompat.ACTION_PLAY_PAUSE)
                .build());
        mediaSession.setMetadata(new MediaMetadataCompat.Builder()
                .putString(MediaMetadataCompat.METADATA_KEY_ARTIST, "Test Artist")
                .putString(MediaMetadataCompat.METADATA_KEY_ALBUM, "Test Album")
                .putString(MediaMetadataCompat.METADATA_KEY_TITLE, "Test Track Name")
                .putLong(MediaMetadataCompat.METADATA_KEY_DURATION, 10000)
                .putBitmap(MediaMetadataCompat.METADATA_KEY_ALBUM_ART,
                    BitmapFactory.decodeResource(getResources(), R.mipmap.ic_launcher))
                .build());

        AudioManager audioManager = (AudioManager) getSystemService(Context.AUDIO_SERVICE);
        audioManager.requestAudioFocus(new AudioManager.OnAudioFocusChangeListener() {
            @Override
            public void onAudioFocusChange(int focusChange) {
                // Ignore
            }
        }, AudioManager.STREAM_MUSIC, AudioManager.AUDIOFOCUS_GAIN);
        mediaSession.setActive(true);
    }

    @Override
    public int onStartCommand(Intent intent, int flags, int startId) {
        if (mediaSession.getController().getPlaybackState().getState() == PlaybackStateCompat.STATE_PLAYING) {
            mediaSession.setPlaybackState(new PlaybackStateCompat.Builder()
                    .setState(PlaybackStateCompat.STATE_PAUSED, 0, 0.0f)
                    .setActions(PlaybackStateCompat.ACTION_PLAY_PAUSE).build());
        } else {
            mediaSession.setPlaybackState(new PlaybackStateCompat.Builder()
                    .setState(PlaybackStateCompat.STATE_PLAYING, 0, 1.0f)
                    .setActions(PlaybackStateCompat.ACTION_PLAY_PAUSE).build());
        }
        return super.onStartCommand(intent, flags, startId);
    }

    @Override
    public IBinder onBind(Intent intent) {
        return null;
    }

    @Override
    public void onDestroy() {
        super.onDestroy();
        mediaSession.release();
    }
}

RemoteReceiver.java

package com.example.remotecontrolclient;

import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.Intent;
import android.view.KeyEvent;

public class RemoteReceiver extends BroadcastReceiver {
    @Override
    public void onReceive(Context context, Intent intent) {
        if (Intent.ACTION_MEDIA_BUTTON.equals(intent.getAction())) {
            final KeyEvent event = intent.getParcelableExtra(Intent.EXTRA_KEY_EVENT);

            if (event != null && event.getAction() == KeyEvent.ACTION_DOWN) {
                switch (event.getKeyCode()) {
                    case KeyEvent.KEYCODE_MEDIA_PLAY_PAUSE:
                        context.startService(new Intent(context, PlayerService.class));
                        break;
                }
            }
        }
    }
}