请教：SurfaceView+mediaplayer有声音无视频是怎么回事？

Question

import android.app.Activity;
import android.media.AudioManager;
import android.media.MediaPlayer;
import android.os.Bundle;
import android.view.SurfaceHolder;
import android.view.SurfaceView;public class MediaPlayDemo extends Activity {
private SurfaceView surfaceView = null ;
private SurfaceHolder surfaceHolder = null ;
private MediaPlayer mp = null ;    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        surfaceView = new SurfaceView(this);
this.surfaceHolder = this.surfaceView.getHolder();
this.surfaceHolder.setType(SurfaceHolder.SURFACE_TYPE_PUSH_BUFFERS);
this.setContentView(this.surfaceView);

this.mp = new MediaPlayer();
try {
mp.setDataSource("/sdcard/wozhinvrenxin.mp4");
} catch (Exception e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
this.mp.setDisplay(surfaceHolder);
this.mp.setAudioStreamType(AudioManager.STREAM_MUSIC);
try {
this.mp.prepare();
} catch (Exception e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
this.mp.start();
    }
}

Answer 1

原因是：MediaPlayer开始播放后，SurfaceView还没有创建出来，因此会出现有声音没图像，解决办法：通过surfaceHolder.addCallback监听surfaceCreate事件后再播放；public class MediaPlayDemo extends Activity implements SurfaceHolder.Callback
{   
private SurfaceView surfaceView = null ;
    private SurfaceHolder surfaceHolder = null ;
    private MediaPlayer mp = null ;    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState)  
    {
        super.onCreate(savedInstanceState);
        surfaceView = new SurfaceView(this);
        surfaceHolder = surfaceView.getHolder();        
        surfaceHolder.setType(SurfaceHolder.SURFACE_TYPE_PUSH_BUFFERS);
        surfaceHolder.addCallback(this);
        setContentView(surfaceView);
            } @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
        mp = new MediaPlayer();        
        mp.setAudioStreamType(AudioManager.STREAM_MUSIC);
        mp.setDisplay(surfaceHolder);
        try {
            mp.setDataSource("/sdcard/DownAndPlay/xyj.mp4");
        } catch (Exception e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        try {
            mp.prepare();
        } catch (Exception e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        mp.start();
} @Override
public void surfaceDestroyed(SurfaceHolder holder) {
// TODO Auto-generated method stub

}}

Answer 2

SurfaceView没有创建成功，所以没有视频