Add support for automatic wake lock acquisition/release in SimpleExoPlayer

[andrewlewis]

[REQUIRED] Use case description

Apps may need to acquire a wake lock when playing audio with the screen off (see #930 for details). For these use cases, it's possible for apps to acquire/release the wake lock themselves but generally will need to keep track of the player state to do this properly.

Proposed solution

Add support in SimpleExoPlayer for automatically acquiring/releasing a wake lock as needed based on player state.

Alternatives considered

n/a

[nomisRev]

Hi,

I'd love to see something like, and/or at least some additional documentation in the documentation. Anyway, I can contribute to this?

Currently, I am using the following solution for this. (This has not been extensively tested in the field).

fun Context.locks(controller: MediaControllerCompat) = object : MediaControllerCompat.Callback() {

  private val acquired = AtomicBoolean(false)

  val wakeLock: PowerManager.WakeLock = (getSystemService(Context.POWER_SERVICE) as PowerManager)
    .newWakeLock(PowerManager.PARTIAL_WAKE_LOCK, "musicservice:wakelock")

  val wifiLock: WifiManager.WifiLock = (applicationContext.getSystemService(Context.WIFI_SERVICE) as WifiManager)
    .createWifiLock(WifiManager.WIFI_MODE_FULL, "musicservice:wifilock")

  override fun onMetadataChanged(metadata: MediaMetadataCompat?) {
    controller.playbackState?.let(this::updateNotification)
  }

  override fun onPlaybackStateChanged(state: PlaybackStateCompat?) {
    state?.let(this::updateNotification)
  }

  private fun updateNotification(state: PlaybackStateCompat) = when (state.state) {
    PlaybackStateCompat.STATE_BUFFERING, PlaybackStateCompat.STATE_PLAYING -> acquire()
    PlaybackStateCompat.STATE_STOPPED, PlaybackStateCompat.STATE_PAUSED -> release()
    else -> { }
  }

  @SuppressLint("WakelockTimeout")
  private fun acquire() {
    if (acquired.compareAndSet(false, true)) {
      Timber.wtf("Releasing WakeLock & WifiLock")
      wakeLock.acquire()
      wifiLock.acquire()
    }
  }

  private fun release() {
    if (acquired.compareAndSet(true, false)) {
      Timber.wtf("Releasing WakeLock & WifiLock")
      wakeLock.release()
      wifiLock.release()
    }
  }
}

And it can be consumed as follows.

private fun MediaBrowserServiceCompat.createMediaController(mediaSession: MediaSessionCompat) =
  MediaControllerCompat(this, mediaSession).apply {
    registerCallback(audioBecomingNoisyHandler(mediaSession.sessionToken))
    registerCallback(locks(controller))
  }