getDuration-获取媒体总长度值为-1

    例如VideoView获取视频总长度:
    在视频播放前获取到的视频总长度都为-1
    想要在视频播放前获取到总长度的话:

    videoView.setOnPreparedListener(new MyOnPreparedListener());
    private class MyOnPreparedListener implements OnPreparedListener{
    
    		@Override
    		public void onPrepared(MediaPlayer mp) {
    			// TODO Auto-generated method stub
    
    			video.getDuration();
    		}
    		
    	}