Android MediaSessionCompat Callbacks not firing

Question

I'm creating an audiobook player, and I'm using MediaSessionCompat related classes to handle notifications. My code is heavily inspired by the android-MediaBrowserService samples ( https://github.com/googlearchive/android-MediaBrowserService ), and i'm not quite understanding it all for the moment ( the createContentIntent espicially )

Here is my simple class in charge of building notifications from a bookPlayer providing metadata and playbackstate data

class PlayerNotificationManager(val playerService: PlayerService) {

    val CHANNEL_ID = "pylvain.gamma"
    val NOTIFICATION_ID = 412
    private val REQUEST_CODE = 501

    val notificationManager =
        playerService.getSystemService(Context.NOTIFICATION_SERVICE) as NotificationManager

    private val playAction: NotificationCompat.Action =
        NotificationCompat.Action (
            android.R.drawable.ic_media_pause,
            "PAUSE",
            buildMediaButtonPendingIntent(
                playerService,
                PlaybackStateCompat.ACTION_PAUSE
            )
        )

    fun getNotification(bookPlayer: BookPlayer): Notification  {

        if (isAndroidOOrHigher()) createChannel()

        val style = androidx.media.app.NotificationCompat.MediaStyle()
            .setMediaSession(playerService.sessionToken)
            .setShowCancelButton(true)
            .setShowActionsInCompactView(0)
            .setCancelButtonIntent(
                buildMediaButtonPendingIntent(
                    playerService,
                    PlaybackStateCompat.ACTION_STOP
                )
            )

        val builder = NotificationCompat.Builder(playerService, CHANNEL_ID)
            .addAction(playAction)
            .setStyle(style)
            .setSmallIcon(R.drawable.ic_music_rest_quarter)
            .setContentIntent(createContentIntent())
            .setVisibility(NotificationCompat.VISIBILITY_PUBLIC)

        return builder.build()

    }

    private fun createContentIntent(): PendingIntent { //TODO: Understand that
        Timber.i("Creating Intent")
        val openUI = Intent(playerService, MainActivity::class.java)
        openUI.flags = Intent.FLAG_ACTIVITY_SINGLE_TOP
        return PendingIntent.getActivity(
            playerService, 0, openUI, PendingIntent.FLAG_UPDATE_CURRENT
        )
    }

The notification is showing perfectly fine with metadata

Here is my MediaBrowserService handling the media session, where I registered the callbacks. The bookplayer is constructed and injected with Koin. :

class PlayerService : MediaBrowserServiceCompat() {

    private lateinit var playerNotificationManager: PlayerNotificationManager
    lateinit var session: MediaSessionCompat

    private val bookPlayer: BookPlayer by inject()

    override fun onCreate() {
        super.onCreate()

        session = MediaSessionCompat(this, "MusicService")
        session.apply {
            setFlags(
                MediaSessionCompat.FLAG_HANDLES_MEDIA_BUTTONS or
                        MediaSessionCompat.FLAG_HANDLES_TRANSPORT_CONTROLS
            )
            setPlaybackState(bookPlayer.playbackState)
            setMetadata(bookPlayer.getMetadata())
            setCallback(callbacks)
            setActive(true)
        }

        setSessionToken(session.sessionToken)
        playerNotificationManager = PlayerNotificationManager(this)

        val notification = playerNotificationManager.getNotification(bookPlayer)

        startForeground(playerNotificationManager.NOTIFICATION_ID, notification)

    }

    override fun onTaskRemoved(rootIntent: Intent?) { //TODO
        super.onTaskRemoved(rootIntent)
        stopSelf()
    }

    override fun onStartCommand(intent: Intent?, flags: Int, startId: Int): Int {
        return super.onStartCommand(intent, flags, startId)
    }

    override fun onGetRoot(
        clientPackageName: String,
        clientUid: Int,
        rootHints: Bundle?
    ): BrowserRoot? {
        return BrowserRoot("root", null)
    }

    override fun onLoadChildren(
        parentId: String, result: Result<MutableList<MediaBrowserCompat.MediaItem>>
    ) {
        result.sendResult(null);
    }
    
    override fun onDestroy() {
        session.release()
    }


    val callbacks = object : MediaSessionCompat.Callback() {

        override fun onCommand(command: String?, extras: Bundle?, cb: ResultReceiver?) {
            Timber.i("Test")
            super.onCommand(command, extras, cb)
        }

        override fun onPrepare() {
            Timber.i("Preparing")
        }

        override fun onPlay() {
            Timber.i("Playing")
            bookPlayer.pause()
        }

        override fun onPause() {
            Timber.i("Pausing")
            bookPlayer.pause()
        }

        override fun onSkipToNext() {}
        override fun onSkipToPrevious() {}
        override fun onStop() {}
        override fun onSeekTo(pos: Long) {}
        override fun onMediaButtonEvent(mediaButtonIntent: Intent): Boolean = true

    }

}

Then the service is started from the main activity with

startService(Intent(mainContext, PlayerService::class.java))

I also added this to my Android manifest

        <service android:name=".playerservice.PlayerService">
            <intent-filter>
                <action android:name="android.media.browse.MediaBrowserService" />
            </intent-filter>
        </service>


        <receiver android:name="androidx.media.session.MediaButtonReceiver">
            <intent-filter>
                <action android:name="android.intent.action.MEDIA_BUTTON" />
            </intent-filter>
        </receiver>

None of the callbacks are called whenever I push the button. when i do, the app log the following text :

D/MediaBrowserCompat: Connecting to a MediaBrowserService.

and nothing happens ... I've searched the entire internet and I'm completely clueless, but it's surely something simple. Can someone help me ? Thank you very much in advance <3

Answer 1

The callback worked ... Just not the way intended. It turns out that the play action button was calling

override fun onMediaButtonEvent(mediaButtonIntent: Intent): Boolean = true

I deleted the function, and ... It works ...

Thank you for your attention !

Answer 2

If you want to get media button, you have to play something. Try to play dummy audio, when your service is started

    // play dummy audio
    AudioTrack at = new AudioTrack(AudioManager.STREAM_MUSIC, 48000, AudioFormat.CHANNEL_OUT_STEREO, AudioFormat.ENCODING_PCM_16BIT,
            AudioTrack.getMinBufferSize(48000, AudioFormat.CHANNEL_OUT_STEREO, AudioFormat.ENCODING_PCM_16BIT), AudioTrack.MODE_STREAM);
    at.play();

    // a little sleep 
    at.stop();
    at.release();

https://stackoverflow.com/a/50678833/9891730 - this is my answer before