使用 asyncTask 播放的音乐不会因使用取消而停止

Question

我正在使用我的活动背景音乐。但是当我想取消它的时候，它不起作用。音乐一直在播放，直到它自己结束。下面是代码:

public class xx extends Activity 
{ BackgroundSound mBackgroundSound = new BackgroundSound();
  @Override
protected void onCreate(Bundle savedInstanceState) 
{ ....
     }
  @Override
protected void onResume() 
{
    super.onResume();
    mBackgroundSound.execute();
}
@Override
protected  void onPause()
  {
      super.onPause();
      mBackgroundSound.cancel(true);
      }

和选项菜单选择:

@Override
public boolean onOptionsItemSelected(MenuItem item) {
    switch (item.getItemId()) {
    case android.R.id.home:
         mBackgroundSound.cancel(true);
                NavUtils.navigateUpFromSameTask(this);
                return true;
    case R.id.menu_Add:
        { mBackgroundSound.cancel(true);
            Intent intent = new Intent(xx.this,yy.class);
                intent.putExtra("flag", "add");
                intent.putExtra("AddObj", "mm");
            startActivity(intent);
            break;
        }
    case R.id.menu_list_quote:
        {
            mBackgroundSound.cancel(true);
            Intent intent = new   Intent(xx.this,zz.class);
                intent.putExtra("Obj", "nn");
            startActivity(intent);
            break;
        }   

    }
    //return true;
    return super.onOptionsItemSelected(item);
}

和asynTask:

 public class BackgroundSound extends AsyncTask<Void, Void, Void> {
     @Override
     protected Void doInBackground(Void... params) {
         try
         {
             while( !isCancelled())
             {
            // FileDescriptor afd = openFd("cock_alarm.mp3");
             MediaPlayer player = new MediaPlayer();
             player.setDataSource(_musicFilePath);
             player.prepare();
             //player.setLooping(true); // Set looping 
             player.setVolume(100,100); 
             player.start(); 
           //  if(isCancelled())
            //   player.stop();
             }
         }
         catch(Exception exp)
         {
             exp.printStackTrace();
         }
         return null;
      }
        }

还有，尝试使用for循环:

  for(int i=0;i<100 && !isCancelled();i++)

and try this inside try block of asyncTask:

if(isCancelled())
 player.stop();

我要怎么解决它?

Answer 1

而不是创建一个AsyncTask，为什么不只是创建MediaPlayer，并从你的活动开始?

MediaPlayer有自己的线程逻辑。您不需要创建一个线程来管理媒体播放器。您可以在这里阅读更多内容:http://developer.android.com/guide/topics/media/mediaplayer.html

在您的活动中，您可以执行以下操作:

private MediaPlayer mMediaPlayer;
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    // Initalize the media player
    mMediaPlayer = ... however you are initializing it ...;
    // Set the listener so the media player can tell you when it is finished preparing
    mMediaPlayer.setOnPreparedListener(this);
    // Prepare the MediaPlayer asynchronously so that the UI thread does not lock up
    mMediaPlayer.prepareAsync();
}
// You need to listen for when the Media Player is finished preparing and is ready
public void onPrepared(MediaPlayer player) {
    // Start the player
    player.start();
}

当你需要停止播放时，只需调用

mMediaPlayer.stop();

Answer 2

vogella在他的网站上解释道:AsyncTask不会自动处理配置更改，也就是说，如果活动被重新创建，程序员必须在他的编码中处理它。

一个常见的解决方案是在一个保留的headless片段中声明AsyncTask。"

查看全文:http://www.vogella.com/tutorials/AndroidBackgroundProcessing/article.html androidbackground