path = "/data/test.mp4";
      mMediaPlayer = new MediaPlayer();
      mMediaPlayer.setDataSource(path);
      mMediaPlayer.setDisplay(holder);
      mMediaPlayer.prepare();
      mMediaPlayer.setOnPreparedListener(this);    public void onPrepared(MediaPlayer mediaplayer) {
        Log.d(TAG, "onPrepared called");
        mVideoWidth = mMediaPlayer.getVideoWidth();
        mVideoHeight = mMediaPlayer.getVideoHeight();
        Log.d(TAG, "mVideoWidth:"+mVideoWidth);
        Log.d(TAG, "mVideoHeight:"+mVideoHeight);
        if (mVideoWidth != 0 && mVideoHeight != 0) {
            holder.setFixedSize(mVideoWidth, mVideoHeight);
            mMediaPlayer.start();
            Log.d(TAG, "mMediaPlayer START " );
        }    }
输出mVideoWidth、mVideoHeight均为0
求指导