在iOS中截取UIView的屏幕截图

我正在运行iOS 4.3&试图拍摄正在播放电影的UIView的截图.
问题是截图(在模拟器中)结果只是一个黑色背景&不是我希望的电影形象.我的代码如下,任何想法可能是什么？提前致谢 ：)

- (void) takeScreenshot;
{

    UIGraphicsBeginImageContextWithOptions(self.frame.size,NO,0.0);
    [self.layer renderInContext:UIGraphicsGetCurrentContext()];
    UIImage *screenshot = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();

    UIImageView *movieImage = [[UIImageView alloc] initWithImage:screenshot];
    [self addSubview:movieImage];

}

UIImage *image = [moviePlayer thumbnailImageAtTime:moviePlayer.currentPlayBACkTime timeOption:MPMovieTimeOptionNearestKeyFrame];