Kotlin media player notification buttons do not take any action

Question

I'm trying to develop a music playback application in kotlin as a foreground service with android studio but I'm having some problems with the notification buttons: I can't assign them a function on music playback.

Here's how I did it:

I created a foreground service with a MediaSessionCompat and a MediaPlayer. I created a MediaSessionCompat.Callback object to override some methods as follow :

private val callback = object: MediaSessionCompat.Callback() {
        override fun onPlay() {
            super.onPlay()
            if( !successfullyRetrievedAudioFocus() ) {
                return;
            }
            Log.i("onPlay : ","ça marche !")
            isPlaying = true
            mediaSession.setActive(true);
            setMediaPlaybackState(PlaybackStateCompat.STATE_PLAYING)
            mediaPlayer.start()
        }

        override fun onPause() {
            super.onPause()
            Log.i("onPause : ","ça marche !")
            if(isPlaying) {
                mediaPlayer.pause()
                isPlaying = false
                setMediaPlaybackState(PlaybackStateCompat.STATE_PAUSED);
            }
        }
...}

Using the following helper method to set the state :

private fun setMediaPlaybackState(state: Int) {
        if (state == PlaybackStateCompat.STATE_PLAYING) {
            stateBuilder.setActions(PlaybackStateCompat.ACTION_PLAY_PAUSE or PlaybackStateCompat.ACTION_PAUSE)
        } else {
            stateBuilder.setActions(PlaybackStateCompat.ACTION_PLAY_PAUSE or PlaybackStateCompat.ACTION_PLAY)
        }
        stateBuilder.setState(state, PlaybackStateCompat.PLAYBACK_POSITION_UNKNOWN, 0f)
        mediaSession.setPlaybackState(stateBuilder.build())
    }

Then in the onCreate() service method, I initialized the mediaSessionCompat object :

stateBuilder = PlaybackStateCompat.Builder()
            .setActions(
                PlaybackStateCompat.ACTION_PLAY
                        or PlaybackStateCompat.ACTION_PAUSE
                        or PlaybackStateCompat.ACTION_SKIP_TO_NEXT
                        or PlaybackStateCompat.ACTION_SKIP_TO_PREVIOUS
                        or PlaybackStateCompat.ACTION_STOP
                        or PlaybackStateCompat.ACTION_SEEK_TO)

val mediaButtonReceiver = ComponentName(applicationContext, MyMediaButtonReceiver::class.java)
mediaSession = MediaSessionCompat(applicationContext, "Tag", mediaButtonReceiver, null)

mediaSession.apply {
       setCallback(callback)
       setPlaybackState(stateBuilder.build())
       setFlags(
           MediaSessionCompat.FLAG_HANDLES_MEDIA_BUTTONS or
                   MediaSessionCompat.FLAG_HANDLES_TRANSPORT_CONTROLS
       )
       setActive(true)
}

I also created a MediaButtonReceiver class to override the onReceive method as needed :

class MyMediaButtonReceiver : MediaButtonReceiver() {

    override fun onReceive(cxt: Context, intent: Intent) {

        val event: KeyEvent?
        val action: Int

        //Log.i("uno", "intent.getAction(): " + intent.action)
        if (Intent.ACTION_MEDIA_BUTTON != intent.action) {
            return
        }

        event = intent.getParcelableExtra<Parcelable>(Intent.EXTRA_KEY_EVENT) as KeyEvent

        //Log.i("uno", "EXTRA_KEY_EVENT: " + event)
        if (event == null) {
            return
        }


        //Log.i("uno", "event.KeyCode: " + event.keyCode)
        when(event.keyCode){
            KeyEvent.KEYCODE_MEDIA_PAUSE -> Log.i("keycode", "KEYCODE_MEDIA_PAUSE")
            KeyEvent.KEYCODE_MEDIA_PLAY -> Log.i("keycode", "KEYCODE_MEDIA_PLAY")
            KeyEvent.KEYCODE_MEDIA_PLAY_PAUSE -> Log.i("keycode", "KEYCODE_MEDIA_PLAY_PAUSE")
            KeyEvent.KEYCODE_MEDIA_PREVIOUS -> Log.i("keycode", "KEYCODE_MEDIA_PREVIOUS")
            KeyEvent.KEYCODE_MEDIA_NEXT -> Log.i("keycode", "KEYCODE_MEDIA_NEXT")
        }
    }

}

And I have referenced it in the manifest :

        <receiver android:name=".MyMediaButtonReceiver"
            android:exported="true"
            tools:ignore="Instantiatable">
            <intent-filter>
                <action android:name="android.intent.action.MEDIA_BUTTON" />
            </intent-filter>
        </receiver>

        <service
            android:name=".MyMediaPlayerService"
            android:exported="true">
            <intent-filter>
                <action android:name="android.intent.action.MEDIA_BUTTON"/>
            </intent-filter>
        </service>

I created a good notification with buttons :

            addAction(
                NotificationCompat.Action(
                    if(isPlaying) R.drawable.ic_play else R.drawable.ic_pause,
                    "Pause",
                    MediaButtonReceiver.buildMediaButtonPendingIntent(
                        applicationContext,
                        PlaybackStateCompat.ACTION_PLAY_PAUSE
                    )
                )
            )
...
setStyle(androidx.media.app.NotificationCompat.MediaStyle()
                .setMediaSession(mediaSession.sessionToken)
                .setShowActionsInCompactView(1)
)

To finish, in the onStartCommand(), I added this command :

MediaButtonReceiver.handleIntent(mediaSession, intent)

Now here are the results I get: when the service starts, the notification appears correctly as a music notification, with the buttons and the playback information. When pressing the pause button for example, I get the corresponding log defined in the MyMediaButtonReceiver class but nothing happens to the music playback. However, the MediaButtonReceiver also takes the information from the headphone buttons for example, and when I plug a headphone into my phone, the next song and previous song buttons work.

Can you help me to identify my error please? Thanks in advance