MPMoviePlayerController 拍摄屏幕截图但仅显示黑屏

我在播放 MPMoviePlayerController 时截取屏幕截图。完美保存屏幕截图，但图像只有黑色。我使用下面的代码。

UIGraphicsBeginImageContext(self.moviePlayerController.view.frame.size);
[self.moviePlayerController.view.layer renderInContext:UIGraphicsGetCurrentContext()];
UIImage *viewImage = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
UIImageWriteToSavedPhotosAlbum(viewImage, nil, nil, nil);

最后我解决了这个问题...我正在使用这段代码...完美工作...感谢所有人...

- (void)captureScreenShot
{
    CGImageRef originalImage = UIGetScreenImage();
    CGImageRef videoImage = CGImageCreateWithImageInRect(originalImage, CGRectMake(0, 66, 320, 230));            
    UIImage *snapShotImage = [UIImage imageWithCGImage:videoImage];
    UIImageWriteToSavedPhotosAlbum(snapShotImage, nil, nil, nil);
    CGImageRelease(originalImage);                
    CGImageRelease(videoImage);  
}