急！！android mediaplayer 有声音无画面 网上方法试过了都不行 下面是我的代码

mPreview = (SurfaceView) findViewById(R.id.surface);
// setContentView(mPreview); // holder是什么
mPreview.getHolder().setFixedSize(176, 144);//设置分辨率
mPreview.getHolder().setType(SurfaceHolder.SURFACE_TYPE_PUSH_BUFFERS);
this.mPreview.getHolder().addCallback(new Callback() { @Override
public void surfaceChanged(SurfaceHolder holder, int format,
int width, int height) {
// TODO Auto-generated method stub }

@Override
public void surfaceCreated(SurfaceHolder holder) {
// TODO Auto-generated method stub
mMdeiaPlayer=new MediaPlayer();
mMdeiaPlayer.setAudioStreamType(AudioManager.STREAM_MUSIC);
mMdeiaPlayer.setDisplay(VideoPlayActivity.this.mPreview.getHolder());
        //设置显示视频显示在SurfaceView上
            try {
             //AssetFileDescriptor aFD = VideoPlayActivity.this.getAssets().openFd(vPath);
             //FileDescriptor fileDescriptor = aFD.getFileDescriptor();
             //mMdeiaPlayer.setDataSource(fileDescriptor, aFD.getStartOffset(), aFD.getLength());
             //aFD.close();
             mMdeiaPlayer.setDataSource(vPath);
             mMdeiaPlayer.prepare();

             mMdeiaPlayer.setOnPreparedListener(new OnPreparedListener() {
        
         @Override
         public void onPrepared(MediaPlayer mp) {
         // TODO Auto-generated method stub
         System.out.println("加载完毕");
         }
         });
             System.out.println("准备好了");
            } catch (Exception e) {
                e.printStackTrace();
            }
            
}[/code]android