获取存储在SD卡上的视频的URL

Question

我在Android中使用JMF库进行视频编辑..我无法获取存储在SD卡中的文件的URL ..我使用了代码

    File sdcard = Environment.getExternalStorageDirectory();
    File file = new File(sdcard, "myvideo.mp4");
    Log.i("dhiraj", file.toURL));
    MediaLocator ml;        

    if((ml=new MediaLocator(file.toURL))==null);{
    Log.i("dhiraj", "ML not created");  
    }