SurfaceView播放视频时只有声音没有图片

如题；
代码如下：videoplayer.xml<?xml version="1.0" encoding="utf-8"?>
<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent" >
<SeekBar 
        android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:id="@+id/skb_video"
    />
<SurfaceView 
    android:id="@+id/vdoplayer"
    android:layout_width="wrap_content" 
    android:layout_height="200dp"
    android:layout_gravity="center"
/>
<LinearLayout 
    android:layout_width="fill_parent"
  android:layout_height="wrap_content"
    android:layout_alignBottom="@id/vdoplayer"
    android:id="@+id/videocontrol"
    >
    <Button 
        android:id="@+id/cmd_play"
        android:layout_width="wrap_content"
  android:layout_height="wrap_content"
  android:layout_marginTop="250dp"
  android:layout_marginLeft="200dp"
  android:text="@string/play"
        />
<Button 
        android:id="@+id/cmd_pause"
        android:layout_width="wrap_content"
  android:layout_height="wrap_content"
  android:layout_marginTop="250dp"
  android:layout_toRightOf="@id/cmd_play"
  android:text="@string/pause"
        />
</LinearLayout>
    
</FrameLayout>VideoPlayer.javapackage www.lemon.mine;import java.util.Timer;
import java.util.TimerTask;import android.app.Activity;
import android.media.AudioManager;
import android.media.MediaPlayer;
import android.os.Bundle;
import android.view.SurfaceHolder;
import android.view.SurfaceHolder.Callback;
import android.view.SurfaceView;
import android.view.View;
import android.view.View.OnClickListener;
import android.view.Window;
import android.view.WindowManager;
import android.widget.Button;
import android.widget.LinearLayout;
import android.widget.SeekBar;public class VideoPlayer extends Activity implements Callback,OnClickListener{
    /** Called when the activity is first created. */

private Button cmd_play =null;
private Button cmd_pause = null;
private Boolean isChanging = true;

private MediaPlayer mp =null;
private SurfaceView surfaceView;
private SurfaceHolder surfaceHolder;
private Timer mTimer;
private TimerTask mTimerTask;

private LinearLayout ll = null;
private SeekBar skb_video = null;
private static final String tag = "mine";

    @Override
    public void onCreate(Bundle icicle) {
        super.onCreate(icicle);
        
        requestWindowFeature(Window.FEATURE_NO_TITLE);//隐藏标题栏
        getWindow().setFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN,
        WindowManager.LayoutParams.FLAG_FULLSCREEN);//隐藏状态栏      
        
        setContentView(R.layout.videoplayer);//设置布局
        
        skb_video = (SeekBar)findViewById(R.id.skb_video);//进度条
        cmd_play = (Button)findViewById(R.id.cmd_play);//播放按钮
        cmd_play.setOnClickListener(this);
        cmd_pause = (Button)findViewById(R.id.cmd_pause);//暂停按钮
        cmd_pause.setOnClickListener(this);
        
Bundle bunde = this.getIntent().getExtras();
String videoPath = bunde.getString("filePath");//得到视频路径

mTimer = new Timer();//计时器
mTimerTask = new TimerTask() {
@Override
public void run() {
if(isChanging==true)
return;
if(mp.getVideoHeight()==0)
skb_video.setProgress(mp.getCurrentPosition());
}
};
mTimer.schedule(mTimerTask, 0, 10);

        surfaceView = (SurfaceView)findViewById(R.id.vdoplayer);//得到播放view
        surfaceHolder = surfaceView.getHolder();
        surfaceHolder.addCallback(this);
        surfaceHolder.setFixedSize(176, 144);//确定大小        surfaceHolder.setType(SurfaceHolder.SURFACE_TYPE_PUSH_BUFFERS);
        
        mp = new MediaPlayer();//设置媒体播放器
mp.setOnCompletionListener(new MediaPlayer.OnCompletionListener(){
@Override
public void onCompletion(MediaPlayer arg0) {

mp.release();
}
});      
        playVideo(videoPath);//播放视频
        skb_video.setMax(mp.getDuration());//设置SeekBar的长度 
        skb_video.setOnSeekBarChangeListener(new SeekBarChangeEvent());               
        
    }
    private void playVideo(String path){//播放视频
    
     try {
mp.setDataSource(path);
mp.setDisplay(surfaceHolder);
        mp.prepare();                  
        mp.setAudioStreamType(AudioManager.STREAM_MUSIC);         
} catch (Exception e) {

e.printStackTrace();
}//读取视频
     mp.start();
    }
    @Override
public void onClick(View v) {//点击按钮事件

 if (v == cmd_play) {
            mp.start();
 } else if (v == cmd_pause) {
            mp.pause();
 } 
}
    protected void onDestroy() {
        
        super.onDestroy();
        
        if(mp.isPlaying()){
         mp.stop();
        }
        mp.release();
    }
    class SeekBarChangeEvent implements SeekBar.OnSeekBarChangeListener{//进度条事件
    
@Override
public void onProgressChanged(SeekBar seekBar, int progress,boolean fromUser) {
   
}

@Override
public void onStartTrackingTouch(SeekBar seekBar) {
isChanging=true;
}

@Override
public void onStopTrackingTouch(SeekBar seekBar) {
mp.seekTo(seekBar.getProgress());
isChanging=false;  
}
    }
@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

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

}
}