Ios 动画不'；滚动UIScrollView时无法工作

我有一个UIScrollView，里面有一堆项目，类似于facebook提要。在这个提要中，我有一堆从互联网上加载的图像。加载图像时，图像淡入。问题是，如果我滚动滚动滚动视图，那么直到我的手指离开滚动视图，图像动画才会淡入。滚动时是否有任何方法更新UIScrollView视图的子视图

-(void)loadStuff:(DipticView*)diptic{
    //DipticView is a UIView subclass that holds the imageview and some other information
    ConnectionManager *conman = [[ConnectionManager alloc] init];
    WebImage *webimage = [diptic.item.images firstObject]; //webimage holds the imageurl and the image

    [conman getImageWithURL:webimage.image_URL inBackgroundWithBlock:^(NSString *error, id image) {
        webimage.image = image;
        diptic.imageView.image = image;
        diptic.imageView.alpha = 0;
        diptic.userInteractionEnabled = NO;
        [UIView animateWithDuration:.4 animations:^{
            diptic.imageView.alpha = 1;
        } completion:^(BOOL finished) {
            diptic.userInteractionEnabled = YES;
        }];
        //The diptics are all subviews of the scrollview.
    }];
}

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但我不确定这种方法是否能很好地用于animateWithDuration。

图像中的淡入度如何？我只是调用UIView animateWithDuration，所以我认为它不仅仅是animateWithDuration。因为它看起来不像康曼完成块中的任何东西正在被执行。我尝试包装整个调用以在dispatch\u async中获取映像，但似乎没有解决问题。

   dispatch_async(dispatch_get_main_queue(), ^{
    [UIView animateWithDuration:.4 animations:^{
        diptic.imageView.alpha = 1;
    } completion:^(BOOL finished) {
        diptic.userInteractionEnabled = YES;
    }];
});