How to support reordering during the shuffle

Things I want to do

• The app shows currently playing items
• The app allows reordering during the shuffle
• The result of reordering during the shuffle does not affect the song order before the shuffle

Current approach

• Get currently playing items from MediaControllerCompat.Callback#onQueueChanged
• Customize TimelineQueueEditor, ShuffleOrder
  • doesn’t call Player#moveMediaItem when reorder during the shuffle
  • generate a new ShuffleOrder from the sorted result
  • call ExoPlayer#setShuffleOrder to update the sort order

Result

• When reordering several times while shuffling, the song order may not be reflected in MediaSession
• doesn’t call MediaControllerCompat.Callback#onQueueChanged

Environment

• ExoPlayer:2.16.1
• Test Device:
  • Pixel 3(OS 12)
  • Pixel 4(OS 11)
  • Emulator(OS 10)
  • Sample Project

Sample Project

• https://github.com/mag0716/SamplePlayer

Question

• Is it correct behavior that sometimes MediaControllerCompat.Callback#onQueueChanged is not executed when ExoPlayer#setShuffleOrder is called?
• Is there a better approach to support reordering during the shuffle?

[tonihei]

Fixed by the commit above.

[marcbaechinger]

You correctly do

player.setShuffleOrder(shuffleOrder);
mediaSessionConnector.invalidateMediaSessionQueue()

It looks to me like you are hitting a bug with the masked timeline. With the above code the MediaSessionConnector invalidates the queue which triggers queueNavigator.onTimelineChanged(player). The TimelineQueueNavigator then calls player.getCurrentTimeline() and receives the masked timeline that is created just at the beginning of ExoPlayerImpl.setShuffleOrder(shuffleOrder). The timeline created at that moment does still include the old shuffleOrder and not the one that is passed to the setter.

Looks like that we need to assign the new shuffleOrder before we create the masking timeline.

If this is true what I’m saying, you should receive the new shuffle order later. When the status update arrives from the playback thread.

This should possibly already do the trick as a workaround:

player.setShuffleOrder(shuffleOrder);
Util.createHandlerForCurrentLooper().post(() -> {
    mediaSessionConnector.invalidateMediaSessionQueue();
});