Question

我正在创建一个音乐播放器应用程序，我会提取活动中的所有歌曲，当您单击该活动时，它将把歌曲传递给播放器活动，但是只要我单击列表中的项目，该应用程序就会崩溃，导致媒体播放器一片空白这是我的代码

//opening player acitivity from adapter
override fun onBindViewHolder(holder: ViewHolder, position: Int) {

        holder.songname.text = songsList[position].title

        holder.itemView.setOnClickListener {
            val i = Intent(context, PlayerActivity::class.java)
            i.putExtra("position", position)
            context.startActivity(i)
        }

这是我的PlayerActivity的代码

class PlayerActivity: AppCompatActivity() {

    private var position: Int = 0
    lateinit var songlist: List<MusicModel>
    lateinit var uri: Uri
    lateinit var mediaPlayer: MediaPlayer

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_player)

        position = intent.getIntExtra("position", -1)

        mediaPlayer = MediaPlayer()

        songlist = getAudio(this)
        if (songlist  != null){
            pausePlay.setImageResource(R.drawable.ic_pause)
            uri = Uri.parse(songlist[position].path)
        }
        if (mediaPlayer == null){
            mediaPlayer = MediaPlayer.create(applicationContext, uri)
            mediaPlayer.stop()
            mediaPlayer.release()
            mediaPlayer.start()
        }
        else{
            mediaPlayer = MediaPlayer.create(this, uri)
            mediaPlayer.start()
        }

    }

    private fun getAudio(context: Context): ArrayList<MusicModel> {
        val audioList : ArrayList<MusicModel> = ArrayList()
        val uri = MediaStore.Audio.Media.EXTERNAL_CONTENT_URI
        val projection = arrayOf(
            MediaStore.Audio.Media.ALBUM,
            MediaStore.Audio.Media.TITLE,
            MediaStore.Audio.Media.DURATION,
            MediaStore.Audio.Media.DATA,
            MediaStore.Audio.Media.ARTIST
        )
        val cursor = context.contentResolver.query(
            uri, projection, null,
            null, null
        )
        if (cursor != null) {
            while (cursor.moveToNext()) {
                val album = cursor.getString(0)
                val title = cursor.getString(1)
                val duration = cursor.getString(2)
                val path = cursor.getString(3)
                val artist = cursor.getString(4)

                val musicModel = MusicModel(album, title, artist, path, duration)

                audioList.add(musicModel)
            }
            cursor.close()
        }
        return audioList
    }
}

这是从日志猫收到的错误 E / AndroidRuntime：致命异常：main 流程：com.example.musicapp，PID：30931 java.lang.RuntimeException：无法启动活动ComponentInfo {com.example.musicapp / com.example.musicapp.PlayerActivity}：java.lang.NullPointerException：MediaPlayer.create（this，uri）不能为null 在android.app.ActivityThread.performLaunchActivity（ActivityThread.java:2956）在android.app.ActivityThread.handleLaunchActivity（ActivityThread.java:3091）在android.app.servertransaction.LaunchActivityItem.execute（LaunchActivityItem.java:78）在android.app.servertransaction.TransactionExecutor.executeCallbacks（TransactionExecutor.java:108）在android.app.servertransaction.TransactionExecutor.execute（TransactionExecutor.java:68）在android.app.ActivityThread $ H.handleMessage（ActivityThread.java:1843）

有人可以帮我解决此问题吗？？

为什么MediaPlayer使应用程序崩溃

0 个答案: