Kotlin MP3 Player Example

 First   we add the following permission to the Manifest file

<uses-permission android:name="android.permission.FOREGROUND_SERVICE" />

Then we add the following libraries to Gradle Dependencies

implementation ("androidx.media3:media3-exoplayer:1.2.1")
implementation ("androidx.media3:media3-ui:1.2.1")
implementation ("androidx.media3:media3-common:1.2.1")
implementation( "androidx.media3:media3-session:1.2.1")

We synchronize them (we SYNC).

 We add the following "val" into the Main Activity.

val player = ExoPlayer.Builder(context).build()
val mediaSession = MediaSession.Builder(context, player).build()
To take this player to a more advanced level
We add the following code into the main activity.
class PlaybackService : MediaSessionService() {
    private var mediaSession: MediaSession? = null

    // Create your Player and MediaSession in the onCreate lifecycle event
    override fun onCreate() {
        super.onCreate()
        val player = ExoPlayer.Builder(this).build()
        mediaSession = MediaSession.Builder(this, player).build()
    }

    // Remember to release the player and media session in onDestroy
    override fun onDestroy() {
        mediaSession?.run {
            player.release()
            release()
            mediaSession = null
        }
        super.onDestroy()
    }
}
For more features
 add this
// This example always accepts the connection request
override fun onGetSession(
    controllerInfo: MediaSession.ControllerInfo
): MediaSession? = mediaSession  
or for new features
add these codes
override fun onStart() {
  val sessionToken = SessionToken(this, ComponentName(this, PlaybackService::class.java))
  val controllerFuture = MediaController.Builder(this, sessionToken).buildAsync()
  controllerFuture.addListener(
    {
        // Call controllerFuture.get() to retrieve the MediaController.
        // MediaController implements the Player interface, so it can be
        // attached to the PlayerView UI component.
        playerView.setPlayer(controllerFuture.get())
      },
    MoreExecutors.directExecutor()
  )
}