Android VideoView播放视频，提示加载框ProgressBar的问题?

我用VideoView播放视频，因为是加载网络视频么，等一会才能加载出来，我想加个加载框ProgressBar来提醒用户等待，我利用Handle每隔半秒就检测视频是否isPlaying中，但是没效果，网上也有用setOnInfoListener这个接口来控制，但是我试过了 没反应。有哪位大神做过类似的程序吗？可否告知一下？谢谢
这是我的代码：

public class PlayVideoActivity extends CommonActivity
{


    @Bind(R.id.playVideo_vv)
    VideoView playVideoVv;
    @Bind(R.id.pb)
    ProgressBar pb;

    private String videoPath;
    @Override
    protected void onCreate(Bundle savedInstanceState)
    {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.playvideoactivity);
        ButterKnife.bind(this);
        initView();
    }

    Handler handler=new Handler();
    Runnable runnable=new Runnable()
    {
        @Override
        public void run()
        {
            if (playVideoVv.isPlaying())
            {
                pb.setVisibility(View.GONE);
            }else{
                pb.setVisibility(View.VISIBLE);
            }
            handler.postDelayed(runnable,500);
        }
    };

    private void initView()
    {
        pb.setVisibility(View.VISIBLE);
        videoPath=getIntent().getStringExtra("videoPath");
        playVideoVv.setVideoPath(videoPath);
        MediaController mediaController = new MediaController(this,false);
        // 设置VideView与MediaController建立关联
        playVideoVv.setMediaController(mediaController);
        // 设置MediaController与VideView建立关联
        mediaController.setMediaPlayer(playVideoVv);
        // 让VideoView获取焦点
        playVideoVv.requestFocus();
        playVideoVv.start();
    }

}