How do you intercept commands with a ForwardingPlayer?

[aljohnston112]

It seemed pretty straightforward to me, but it is not working as expected.

I have a MediaBrowser that I am using as a MediaController for a MediaLibraryService.MediaLibrarySession

I set up the ForwardingPlayer like so

class MyPlayer(
    private var context: Context?,
    private val mediaItemCreator: MediaItemCreator
) : ForwardingPlayer(
    ExoPlayer.Builder(context!!)
        .setSkipSilenceEnabled(true)
        .setSeekParameters(SeekParameters.EXACT)
        .build()
) {

    private lateinit var _playlist: ProbabilityMap<MusicFile>

    fun setPlaylist(playlist: ProbabilityMap<MusicFile>) {
        _playlist = playlist
    }

    override fun getAvailableCommands(): Player.Commands {
        return super.getAvailableCommands()
            .buildUpon()
            .add(COMMAND_SEEK_TO_NEXT_MEDIA_ITEM)
            .add(COMMAND_SEEK_TO_NEXT)
            .build()
    }

    override fun isCommandAvailable(command: Int): Boolean {
        return availableCommands.contains(command)
    }

    override fun setMediaItem(mediaItem: MediaItem) {
        val next = mediaItemCreator.getMediaItem(
            context!!,
            _playlist.sample().id
        )
        super.setMediaItems(listOf(mediaItem, next))
    }

    override fun seekToNextMediaItem() {
        if(::_playlist.isInitialized) {
            val next = mediaItemCreator.getMediaItem(
                context!!,
                _playlist.sample().id
            )
            replaceMediaItem(mediaItemCount - 1, next)
            seekTo(
                currentMediaItemIndex + 1,
                C.TIME_UNSET
            )
            val afterNext = mediaItemCreator.getMediaItem(
                context!!,
                _playlist.sample().id
            )
            addMediaItem(afterNext)
        }
    }

    override fun release() {
        super.release()
        context = null
    }

}

The command methods do get called, but COMMAND_SEEK_TO_NEXT_MEDIA_ITEM is not always available to the controller.

Then when the controller method setMediaItem is called, the MyPlayer.setMediaItem method is not called.

This issue I made earlier has more details:
#1021

[aljohnston112]

I did some more debugging and it turns out the mappings from controller calls to player calls are not one-to-one and there is no mapping in the docs: https://developer.android.com/reference/androidx/media3/session/MediaController#setMediaItem(androidx.media3.common.MediaItem)

In particular, setMediaItem from the controller calls setMediaItems in the player. I have verified with the debugger and this code in MyPlayer.

    override fun setMediaItems(mediaItems: MutableList<MediaItem>, resetPosition: Boolean) {
        super.setMediaItems(mediaItems, resetPosition)
    }

I think this is an issue because if I override what commands are available (which are overridden in some circumstances for some reason), I expect to be able to know which ForwardingPlayer overrides I will need to provide for said command for the custom behaviors of my app.

Are the mappings for this type of thing documented somewhere? Are they consistent? Are these subject to change?

[tonihei]

Are the mappings for this type of thing documented somewhere? Are they consistent? Are these subject to change?

We attempt to call the same Player method as far as possible, but sometimes need to change it slightly depending on the available commands and parameters we need to pass in. I think from your perspective, it's best to implement all the methods you declare as available via the commands without making assumptions which one is called exactly.

I expect to be able to know which ForwardingPlayer overrides I will need to provide for said command

All these command codes fully list the methods that need to be implemented for this code. Example: https://developer.android.com/reference/androidx/media3/common/Player#COMMAND_SET_SPEED_AND_PITCH() explains how COMMAND_SET_SPEED_AND_PITCH maps to setPlaybackParametersandsetPlaybackSpeed`.

[aljohnston112]

Thank you so much for the explanation! That page looks like a fantastic resource for this.