问用media3播放背景音乐

EN

    class MusicPlayerActivity : BaseActivity() {

    lateinit var musicPlayerBinding: ActivityMusicPlayerBinding
    var player: Player? = null
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        musicPlayerBinding = ActivityMusicPlayerBinding.inflate(layoutInflater)
        setContentView(musicPlayerBinding.root)
        bindMusicService()
    }

    override fun onBackPressed() {
        unbindService(playerServiceConnection)
        if (player?.isPlaying!!) {
            player?.stop()
        }
        player?.release()
        player = null
        super.onBackPressed()
    }
    
    private fun bindMusicService() {
        val intent = Intent(this, PlayerService::class.java)
        bindService(intent, playerServiceConnection, Context.BIND_AUTO_CREATE)
    }

    private val playerServiceConnection = object : ServiceConnection {
        override fun onServiceConnected(name: ComponentName?, service: IBinder?) {
            val binder = service as PlayerService.ServiceBinder
            player = binder.getPlayerService().player!!
            player?.prepare()
            player?.playWhenReady = false
            player?.seekTo(0, 0)
            val mediaMetaData = MediaMetadata.Builder()
                .setAlbumTitle(MusicPlayerData.audioTitle)
                .build()
            val mediaItem =
                MediaItem.Builder().setMediaMetadata(mediaMetaData)
                    .setUri(MusicPlayerData.audioUri)
                    .build()
            player?.setMediaItem(mediaItem)
            setPlayerControls()
        }

        override fun onServiceDisconnected(name: ComponentName?) {
            TODO("Not yet implemented")
        }
    }

    private fun setPlayerControls() {
        musicPlayerBinding.playerView.player = player
        musicPlayerBinding.controls.player = player
        player?.addListener(object : Player.Listener {
            override fun onPlaybackStateChanged(playbackState: Int) {
                super.onPlaybackStateChanged(playbackState)
                when (playbackState) {
                    Player.STATE_BUFFERING -> show(musicPlayerBinding.progressCircular)
                    Player.STATE_READY -> {
                        player?.playWhenReady = true
                        hide(musicPlayerBinding.progressCircular)
                    }
                }
            }
        })
    }
}

class PlayerService : Service() {

private val iBinder = ServiceBinder()
var player: Player? = null
private var mediaSession: MediaSession? = null
lateinit var notificationManager: PlayerNotificationManager

inner class ServiceBinder : Binder() {
    fun getPlayerService(): PlayerService = this@PlayerService
}


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

override fun onCreate() {
    super.onCreate()
    player = ExoPlayer.Builder(this).build()
    mediaSession =
        MediaSession.Builder(this, player!!).setSessionActivity(pendingIntent()!!).setId(Random(5).toString())
            .build()
    notificationManager = PlayerNotificationManager.Builder(this, 111, "Music Channel")
        .setChannelImportance(IMPORTANCE_HIGH)
        .setSmallIconResourceId(R.drawable.music)
        .setChannelDescriptionResourceId(R.string.app_name)
        .setChannelNameResourceId(R.string.app_name)
        .setMediaDescriptionAdapter(audioDescriptor)
        .setNotificationListener(notificationListener)
        .build()


    notificationManager.setPlayer(player)
    notificationManager.setPriority(PRIORITY_MAX)
    notificationManager.setUseRewindAction(true)
    notificationManager.setUseFastForwardAction(false)
    notificationManager.setUsePreviousAction(false)
    notificationManager.setUsePlayPauseActions(true)
}


override fun onDestroy() {
    if (player?.isPlaying!!) {
        player?.stop()
    }
    notificationManager.setPlayer(null)
    player?.release()
    player = null
    stopForeground(true)
    stopSelf()
    super.onDestroy()
}

private val notificationListener = object : PlayerNotificationManager.NotificationListener {
    override fun onNotificationCancelled(notificationId: Int, dismissedByUser: Boolean) {
        super.onNotificationCancelled(notificationId, dismissedByUser)
        stopForeground(true)
        if (player?.isPlaying!!) {
            player?.stop()
            player?.release()
        }
    }

    override fun onNotificationPosted(
        notificationId: Int,
        notification: Notification,
        ongoing: Boolean
    ) {
        super.onNotificationPosted(notificationId, notification, ongoing)
        startForeground(notificationId, notification)
    }
}

private val audioDescriptor = object : PlayerNotificationManager.MediaDescriptionAdapter {
    override fun getCurrentContentTitle(player: Player): CharSequence {
        return player.currentMediaItem?.mediaMetadata?.albumTitle!!
    }

    override fun createCurrentContentIntent(player: Player): PendingIntent? {
        return pendingIntent()
    }

    override fun getCurrentContentText(player: Player): CharSequence? {
        return ""
    }

    override fun getCurrentLargeIcon(
        player: Player,
        callback: PlayerNotificationManager.BitmapCallback
    ): Bitmap? {
        val bitmapDrawable: BitmapDrawable =
            ContextCompat.getDrawable(
                applicationContext,
                R.drawable.cma_logo_render
            ) as BitmapDrawable
        return bitmapDrawable.bitmap
    }
}

private fun pendingIntent(): PendingIntent? {
    val intent = Intent(applicationContext, MusicPlayerActivity::class.java)
    return PendingIntent.getActivity(
        applicationContext,
        0,
        intent,
        PendingIntent.FLAG_UPDATE_CURRENT or PendingIntent.FLAG_IMMUTABLE
    )
}