How to pass raw resource id data from activity to service?

I was asked to display list of songs, playing, pausing, and stopping only using Android core components.

I've managed to display songs list. Also I have implemented play/pause/stop functionality but the problem is that I can only play hardcoded music files.

This is my onCreate function from the Service class:

override fun onCreate() { 
     super.onCreate() 
     mediaPlayer = MediaPlayer.create(this,R.raw.sampl) 
     mediaPlayer.setOnCompletionListener { 
         stopSelf() 
     } 
 }

Basically, my goal is to be able to change that R.raw.sampl with any other file from my raw folder that user chooses from the fragment.

This is how I am playing music in Fragment

binding.btnPlay.setOnClickListener {
            val intent = Intent(requireContext(), MusicService::class.java)
            intent.action = MusicService.ACTION_PLAY
            requireActivity().startService(intent)
        }

private fun listRaw() {
    val fields: Array<Field> = R.raw::class.java.fields
    for (count in fields.indices) {
        val resourceID = fields[count].getInt(fields[count])
    }
}

The above code can be used to list all the files from the raw folder and use the resource id to play them inside the media player.

mediaPlayer = MediaPlayer.create(this,resourceID) 

resourceID will be same as R.raw.sampl

For Activity to Service communication, it is advised to use Binder.
Watch this video for getting a better understanding on service.

MyService class

class MyService : Service() {

    private val binder = MyServiceBinder()

    override fun onBind(intent: Intent): IBinder {
        return binder
    }

    fun playMusic(ab: Int) {
        val mediaPlayer = MediaPlayer.create(this,ab)
        mediaPlayer.start()
    }

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

    inner class MyServiceBinder : Binder(){
        fun getService() = this@MyService
    }
}

And in the activity

private lateinit var myService: MyService
private val connection = object : ServiceConnection{
    override fun onServiceConnected(p0: ComponentName?, p1: IBinder?) {
        val binder = p1 as MyService.MyServiceBinder
        myService = binder.getService()
    }

    override fun onServiceDisconnected(p0: ComponentName?) {

    }

}

override fun onStart() {
    super.onStart()
    Intent(this,MyService::class.java).also{
        bindService(it,connection,Context.BIND_AUTO_CREATE)
        startService(it)
    }
}

override fun onStop() {
    super.onStop()
    unbindService(connection)
}

And on button click or whenever you want to play music. Instead of R.raw.ab use the resourceID

if (::myService.isInitialized) {
                myService.playMusic(R.raw.ab)
            }

You can pass your raw resource id to your service via intent:

binding.btnPlay.setOnClickListener {
    val intent = Intent(requireContext(), MusicService::class.java)
    intent.putExtra("playSong", R.raw.sampl)
    intent.action = MusicService.ACTION_PLAY
    requireActivity().startService(intent)
}

Then, get your resource id in the service:

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

   if (intent != null && intent.extras != null) {
      val songResId = intent.getIntExtra("playSong", -1)
    
      if (songResId != -1) {
         //play song
      }