Objective c 如何在设置图像动画时拍摄UIImageView的屏幕截图

我试图捕捉屏幕，当它在图像视图中只有一个图像时，它工作得非常完美……但是当我为UIImageView设置动画时，我得到的是一个空白的屏幕截图

  CGRect rect = [self.view bounds];
  UIGraphicsBeginImageContext(rect.size);
  CGContextRef context = UIGraphicsGetCurrentContext();
  [self.view.layer renderInContext:context];
  UIImage *capturedScreen = UIGraphicsGetImageFromCurrentImageContext();
  UIGraphicsEndImageContext();
  UIImageWriteToSavedPhotosAlbum(capturedScreen, nil, nil, nil);

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我不知道我的答案是对还是错，但我试着这样做。。。 多亏了

-（无效）更改
{
如果（i>=imags.count-1）
i=0；
其他的
i++；
}
-（空）图像
{
NSArray*imagenames=@[@“1.png”、@“b.png”、@“c.png”]；
int j；
NSMutableArray*图像=[[NSMutableArray alloc]init]；
对于（j=0；j
    -(void)change
     {
       if (i>=imags.count-1)
       i=0;
       else
       i++;
     }
    -(void)images      
       {
        NSArray *imagenames = @[@"1.png",@"b.png",@"c.png"];
        int j;
        NSMutableArray *images= [[NSMutableArray alloc]init];
           for (j=0; j<imagenames.count; j++)
               [images addObject:[UIImage imageNamed:[imagenames objectAtIndex:j]]];
        self.imageview1.animationImages = images;
        self.imageview1.animationDuration =1;
        [NSTimer scheduledTimerWithTimeInterval:1 target:self selector:@selector(change) userInfo:nil repeats:YES];
        [self.bground startAnimating];
        }
      -(IBAction)captureImage:(id)sender
      {
       self.imageview2.image = [images objectAtIndex:i];
       CGRect rect = [self.view bounds];
       UIGraphicsBeginImageContext(rect.size);
       CGContextRef context = UIGraphicsGetCurrentContext();
       [self.view.layer renderInContext:context];
       UIImage *capturedScreen = UIGraphicsGetImageFromCurrentImageContext();
       UIGraphicsEndImageContext();
       UIImageWriteToSavedPhotosAlbum(capturedScreen, nil, nil, nil);


      }