Android - MediaPlayer错误

Question

我正在开发一款播放背景音乐的应用。音乐由在后台运行的服务管理。在Main活动中，在onCreate（）方法中，服务以：

开头

public class MainActivity extends AppCompatActivity {

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    // Background music service.
    Intent musicServiceIntent = new Intent(this, BackgroundSoundService.class);
    startService(musicServiceIntent);

    final BackgroundSoundService bss = new BackgroundSoundService();
    buttonStart = (Button) v.findViewById(R.id.button_start);
    buttonStart.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            bss.onStart();
        }
    });
    buttonPause = (Button) v.findViewById(R.id.button_pause);
    buttonPause.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            bss.onPause();
        }
    });
    buttonStop = (Button) v.findViewById(R.id.button_stop);
    buttonStop.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                bss.onStop();
            }
        });
    }
}
}

该服务是以下代码： 的 BackgroundSoundService.java

    public class BackgroundSoundService extends Service {
    private static final String TAG = null;
    static MediaPlayer mMediaPlayer;

        @Nullable
        @Override
        public IBinder onBind(Intent intent) {
            return null;
        }

       @Override
        public void onCreate() {
            super.onCreate();

            mMediaPlayer = MediaPlayer.create(getApplicationContext(), R.raw.background_music);
            mMediaPlayer.setVolume(1.0f, 1.0f);
            mMediaPlayer.setOnCompletionListener(new MediaPlayer.OnCompletionListener() {
                public void onCompletion(MediaPlayer arg0) {
                    playMusic();
                }
            });

            playMusic();
        }

        public void playMusic() {
            mMediaPlayer.start();
        }

        /**
         *
         * @param arg0 -
         * @return -
         */
        public IBinder onUnBind(Intent arg0) {
            // TO DO Auto-generated method
            return null;
        }

        /**
         *
         */
        public void onStart() {
            Log.d("A", "onStart()");
            if(!mMediaPlayer.isPlaying()) {
                Log.d("A", "mMediaPlayer is not playing");
                playMusic();

            } else {
                Log.d("A", "mMediaPlayer is playing");
            }
        }

        /**
         *
         */
        public void onPause() {
            Log.d("A", "onPause()");
            if(mMediaPlayer.isPlaying()) {
                Log.d("A", "mMediaPlayer is playing");
                mMediaPlayer.pause();
            } else {
                Log.d("A", "mMediaPlayer is not playing");
            }
        }

        /**
         *
         */
        public void onStop() {
            Log.d("A", "onStop()");
            if(mMediaPlayer.isPlaying()) {
                Log.d("A", "mMediaPlayer is playing");
                mMediaPlayer.stop();
            } else {
                Log.d("A", "mMediaPlayer is not playing");
            }
        }

        /**
         *
         */
        @Override
        public void onDestroy() {
            Log.d("A", "onDestroy()");
            mMediaPlayer.stop();
            mMediaPlayer.release();
        }

        /**
         *
         */
        @Override
        public void onLowMemory() {

        }

    }

现在，MainActivity有三个按钮来控制音乐。 SART按钮，启动音乐，PAUSE按钮，暂停声音和STOP按钮，停止音乐。每个都在BackgroundSoundService中的Pause（）和onStop（）上执行方法onStart（）。问题是如果我在STOP按钮后按下START按钮，日志会显示此错误：

E/MediaPlayer: start called in state 0
E/MediaPlayer: error (-38, 0)

我尝试解决这个问题：

    mMediaPlayer.setOnPreparedListener(new MediaPlayer.OnPreparedListener() {
        @Override
        public void onPrepared(MediaPlayer mp) {
            mp.start();
        }
    });

但没有奏效。有什么建议？谢谢。

Answer 1

发布MainActivity代码有助于我们提供精确的解决方案，而不会让您偏离随机答案。

Answer 2

.stop()之后，如果您想再次启动，则需要重置它。

     public void onStop() {
                Log.d("A", "onStop()");
                if(mMediaPlayer.isPlaying()) {
                    Log.d("A", "mMediaPlayer is playing");
            mMediaPlayer.stop();
            mMediaPlayer.reset();
            mMediaPlayer = MediaPlayer.create(getApplicationContext(), R.raw.background_music);

                } else {
                    Log.d("A", "mMediaPlayer is not playing");
                }
            }

修改

boolean isPrepared = false;

mMediaPlayer.setOnPreparedListener(new MediaPlayer.OnPreparedListener() {
        @Override
        public void onPrepared(MediaPlayer mp) {
            isPrepared = true;
        }
    });

 public void playMusic() {
   if(isPrepared){
            mMediaPlayer.start();
            isPrepared = false;
     }
    else{
    Toast.makeText(getApplicationContext(),"Not prepared",LENGTH.SHORT)
    .show();
    }
  }

Answer 3

1. 取代mediaPlayer.create（），调用new mediaplayer
2. 在playMusic（）中调用prepare（）和start（） 要么 playMusic（）中的prepareAsync（）和onPreparedListener（）调用start（）