尝试观看视频时模拟器上出现空白屏幕？安卓

Question

我一直在尝试在 Android 模拟器（2.3.3）上播放我的 .3pg 文件，但是我得到的只是一个空白屏幕？有人知道我的代码有什么问题吗？

public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.main);

    SurfaceView surfaceView;
    SurfaceHolder surfaceHolder = null;
    MediaPlayer mediaplayer = new MediaPlayer();
    mediaplayer.setAudioStreamType(AudioManager.STREAM_MUSIC);
    mediaplayer.setDisplay(surfaceHolder);

    getWindow().setFormat(PixelFormat.UNKNOWN);
    surfaceView = (SurfaceView)findViewById(R.id.surfaceview);
    surfaceHolder = surfaceView.getHolder();
    surfaceHolder.addCallback(this);
    surfaceHolder.setFixedSize(176, 144);
    surfaceHolder.setType(SurfaceHolder.SURFACE_TYPE_PUSH_BUFFERS);
    mediaplayer = new MediaPlayer();
    mediaplayer.setAudioStreamType(AudioManager.STREAM_MUSIC);
    try {
        mediaplayer.setDataSource("/sdcard/sample.3gp");
    } catch (IllegalArgumentException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    } catch (IllegalStateException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    } catch (IOException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }
    try {
        mediaplayer.prepare();
    } catch (IllegalStateException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    } catch (IOException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }
    mediaplayer.start();
}

@Override
public void surfaceChanged(SurfaceHolder arg0, int arg1, int arg2, int arg3) {
    // TODO Auto-generated method stub

}

@Override
public void surfaceCreated(SurfaceHolder arg0) {
    // TODO Auto-generated method stub

}

@Override
public void surfaceDestroyed(SurfaceHolder arg0) {
    // TODO Auto-generated method stub

}

}