Сбор элементов мультимедиа с помощью MediaBrowserCompat.Mediaitem

Question

Мой текущий подход к получению всех файлов Musik - это Resolver и Cursor. Теперь я прочитал, есть лучшие методы. Я пытался использовать MediaBrowserCompat.MediaItem но, видимо, я не получаю должного вывода? Мой onLoadChildren функционирует просто неправильно или я называю это неправильно в основной активности?

Основная деятельность:

package com.name.mediabrowsertest

    import android.content.ComponentName
    import android.content.Context
    import android.content.res.Configuration
    import android.media.AudioManager
    import android.media.session.MediaController
    import android.os.Build

    import android.support.v7.app.AppCompatActivity
    import android.os.Bundle
    import android.provider.MediaStore
    import android.support.annotation.RequiresApi
    import android.support.v4.media.MediaBrowserCompat
    import android.support.v4.media.MediaMetadataCompat
    import android.support.v4.media.session.MediaControllerCompat
    import android.support.v4.media.session.PlaybackStateCompat
    import android.util.Log
    import android.view.View
    import android.widget.ImageView


    class MainActivity : AppCompatActivity() {
        private lateinit var mMediaBrowser: MediaBrowserCompat
        fun buildTransportControls(){
            var mMediaItems = mMediaBrowser.subscribe(mMediaBrowser.root,object: MediaBrowserCompat.SubscriptionCallback(){})


            var mPlayPause = findViewById<ImageView>(R.id.imageView)
            //Attach listen to button
            mPlayPause.setOnClickListener(object: View.OnClickListener {
                override fun onClick(v : View ){
                    var pbSate = MediaControllerCompat.getMediaController(this@MainActivity).playbackState.playbackState
                    if(pbSate == PlaybackStateCompat.STATE_PLAYING){
                        MediaControllerCompat.getMediaController(this@MainActivity).transportControls.pause()
                    }else{
                        var test = MediaBrowserCompat.MediaItem.CONTENTS_FILE_DESCRIPTOR
                        Log.i("TEST",test.toString())
                        MediaControllerCompat.getMediaController(this@MainActivity).transportControls.playFromMediaId(MediaBrowserCompat.EXTRA_MEDIA_ID,null)
                        MediaControllerCompat.getMediaController(this@MainActivity).transportControls.play()

                        //MediaControllerCompat.getMediaController(this@MainActivity).transportControls.playFromMediaId()
                        Log.i("TEST","TEST")

                    }
                }
            })
            var  mediaController = MediaControllerCompat.getMediaController(this@MainActivity)

            //Show Init state
            var metadat = mediaController.metadata
            var pbState = mediaController.playbackState

            //Register Callback to stay synced
            mediaController.registerCallback(controllerCallback)



        }
        val controllerCallback = object : MediaControllerCompat.Callback() {
            override fun onMetadataChanged(metadat:MediaMetadataCompat){

                Log.i("Musik",metadat.toString())

            }

            override fun onPlaybackStateChanged(state :PlaybackStateCompat){}
        }

        private val mConnectionCallbacks = object : MediaBrowserCompat.ConnectionCallback() {
            override fun onConnected() {
                Log.i("Connection","Connecting")
                // Get the token for the MediaSession
                val token = mMediaBrowser.sessionToken

                // Create a MediaControllerCompat
                val mediaController = MediaControllerCompat(this@MainActivity,token)

                // Save the controller
                MediaControllerCompat.setMediaController(this@MainActivity, mediaController)

                // Finish building the UI
                buildTransportControls()
            }

            override fun onConnectionSuspended() {
                // The Service has crashed. Disable transport controls until it automatically reconnects
                Log.i("ERROR","Connection Suspended")
            }

            override fun onConnectionFailed() {
                // The Service has refused our connection
                Log.i("ERROR","Connection Failed")
            }
        }

        override fun onCreate(savedInstanceState: Bundle?) {
            super.onCreate(savedInstanceState)
            setContentView(R.layout.activity_main)
            Log.i("Hello World","Hello")
            //Create MediaBrowser Service
            mMediaBrowser = MediaBrowserCompat(this,
                    ComponentName(this, MediaPlaybackService::class.java),
                    mConnectionCallbacks,
                    null)
            Log.i("Hello World","Hello2")


        }

        override fun onStart() {
            super.onStart()
            mMediaBrowser.connect()

        }

        override fun onResume() {
            super.onResume()
            volumeControlStream = AudioManager.STREAM_MUSIC
        }

        override fun onStop() {
            super.onStop()
            if(MediaControllerCompat.getMediaController(this@MainActivity) != null){
                MediaControllerCompat.getMediaController(this@MainActivity).unregisterCallback(controllerCallback)

            }
            mMediaBrowser.disconnect()
        }

    }

Обслуживание:

package com.name.mediabrowsertest


import android.media.MediaDescription
import android.media.browse.MediaBrowser
import android.media.session.MediaSession
import android.os.Build
import android.os.Bundle
import android.support.annotation.RequiresApi
import android.support.v4.media.MediaBrowserCompat
import android.support.v4.media.MediaBrowserServiceCompat
import android.support.v4.media.MediaDescriptionCompat
import android.support.v4.media.session.MediaSessionCompat
import android.support.v4.media.session.PlaybackStateCompat
import android.util.Log


class MediaPlaybackService: MediaBrowserServiceCompat(){

    private val MY_MEDIA_ROOT_ID  = "MediaStore.Audio.Media.EXTERNAL_CONTENT_URI"

    private lateinit var mMediaSession: MediaSessionCompat
    private lateinit var mStateBuilder : PlaybackStateCompat.Builder
    private var  MySessionCallback =object : MediaSessionCompat.Callback() {
        override fun onPause() {
            super.onPause()
        }

        override fun onPlay() {
            super.onPlay()
        }
    }

    override fun onCreate() {
        super.onCreate()
        //Create the MediaSession
        mMediaSession = MediaSessionCompat(this,"PLAYER")
        //Setting the necessary Flags (Media Buttons)
        mMediaSession.setFlags(
                MediaSessionCompat.FLAG_HANDLES_MEDIA_BUTTONS or MediaSessionCompat.FLAG_HANDLES_TRANSPORT_CONTROLS)
        //Set an inital PlaybackStatewith ACTION_BUTTONS, so Media  buttons can start the player
        mStateBuilder = PlaybackStateCompat.Builder().setActions(
                PlaybackStateCompat.ACTION_PLAY or PlaybackStateCompat.ACTION_PAUSE)
        //Set our PLaybackState for the MediaSession
        mMediaSession.setPlaybackState(mStateBuilder.build())

        //Handles callbacks from Media Controller MySessionCalback is a PlaeHolder
        mMediaSession.setCallback(MySessionCallback)
        //Set SessionToken so Activites can communicate with it
        sessionToken = mMediaSession.sessionToken



    }

    override fun onLoadChildren(parentId: String, result: Result<MutableList<MediaBrowserCompat.MediaItem>>) {
        var mediaItems:ArrayList<MediaBrowserCompat.MediaItem> = ArrayList()

        var builder  = MediaDescriptionCompat.Builder()
        builder.setDescription("T")

        builder.setTitle("Media Items")
        var mediaItem = MediaBrowserCompat.MediaItem(builder.build(),MediaBrowser.MediaItem.FLAG_PLAYABLE)
        mediaItems.add(mediaItem)
        var res = mediaItems.toMutableList()
        for(x in res){
            Log.i("Musik",x.toString())
        }
        result.sendResult(res)

    }

    override fun onGetRoot(clientPackageName: String, clientUid: Int, rootHints: Bundle?): BrowserRoot? {

        return BrowserRoot(MY_MEDIA_ROOT_ID,null)

    }



}