媒体播放器不播放

Question

恐怕还有更多的菜鸟问题！

我有一个应用程序，到目前为止，片段中有一个按钮，我需要充当播放暂停按钮，目前我还没有从应用程序中获得任何音频，但它可以稳定地放在手机上。 媒体播放器有自己的服务：

class playerService : Service() {

var isPlaying:Boolean? = null
val player = MediaPlayer()

inner class playerServiceBinder : Binder()
{
    fun getService() : playerService
    {
        return this@playerService // the outer 'this'
    }
}

val mediaFile =      File("${Environment.getExternalStorageDirectory().getAbsolutePath()}/SD_card/Music/Over_the_Horizon.mp3")
override fun onBind(intent: Intent): IBinder? {

   // player.setAudioStreamType(AudioManager.STREAM_MUSIC)
//        player.setDataSource(applicationContext, Uri.fromFile(mediaFile))

    return playerServiceBinder()
}

override fun onStartCommand(intent: Intent?, flags: Int, startId: Int): Int {

    // do something, e.g. start thread, AsyncTask, Anko doAsync, etc.
    player.setAudioStreamType(AudioManager.STREAM_MUSIC)
    player.setDataSource(applicationContext, Uri.fromFile(mediaFile))
    player.setOnPreparedListener { player ->
        player.start()
    isPlaying = true
    }
    player.prepareAsync()
    return START_STICKY

}


fun playPause(){
    if (isPlaying == true){
        player.stop()
    }else{
        player.start()
    }
}
}

这是片段：

class HomeFragment : Fragment() {

private lateinit var homeViewModel: HomeViewModel

override fun onCreateView(
        inflater: LayoutInflater,
        container: ViewGroup?,
        savedInstanceState: Bundle?
): View? {

    homeViewModel =
            ViewModelProviders.of(this).get(HomeViewModel::class.java)
    val root = inflater.inflate(R.layout.fragment_home, container, false)
    val textView: TextView = root.findViewById(R.id.text_home)
    homeViewModel.text.observe(viewLifecycleOwner, Observer {
        textView.text = it
    })
    root.btn_PlayPause.setOnClickListener{ view ->
        playerService().playPause()
    }

    return root
}
}

到目前为止，应用程序启动并且按钮单击但是它没有播放音乐文件并且按钮也没有启动它......我需要做什么才能让按钮控制音乐？