问题描述

使用 AFNetworking，从服务器下载图像并放入 UIImageView 非常简单:

With AFNetworking, is very simple to download an image from a server and put into an UIImageView:

[imageView setImageWithURL:[NSURL URLWithString:@"http://i.imgur.com/r4uwx.jpg"] placeholderImage:[UIImage imageNamed:@"placeholder-avatar"]];

如果我想用效果(可能会褪色)替换图像呢?

How about if I want to do this replacement of image with an effect (maybe fade)???

因为我想用很多图片制作幻灯片.

It's because I want to make a slideshow with a lot of images.

推荐答案

您可以将 animateWithDuration 与提供 success 块，例如

You can use animateWithDuration in conjunction with the rendition of setImageWithURL that supplies the success block, e.g.

[imageView setImageWithURL:[NSURL URLWithString:@"http://i.imgur.com/r4uwx.jpg"] 
          placeholderImage:[UIImage imageNamed:@"placeholder-avatar"]
                   success:^(NSURLRequest *request, NSHTTPURLResponse *response, UIImage *image) {
                       self.imageView.alpha = 0.0;
                       self.imageView.image = image;
                       [UIView animateWithDuration:0.25
                                        animations:^{
                                            self.imageView.alpha = 1.0;
                                        }];
                   }
                   failure:NULL];

或者，如果您的占位符图像不是空白，您可能希望通过 transitionWithView 进行交叉溶解:

Or, if you placeholder image isn't blank, you would probably want to cross dissolve via transitionWithView:

[imageView setImageWithURL:[NSURL URLWithString:@"http://i.imgur.com/r4uwx.jpg"] 
          placeholderImage:[UIImage imageNamed:@"placeholder-avatar"]
                   success:^(NSURLRequest *request, NSHTTPURLResponse *response, UIImage *image) {
                       [UIView transitionWithView:self.imageView
                                         duration:0.3
                                          options:UIViewAnimationOptionTransitionCrossDissolve
                                       animations:^{
                                           self.imageView.image = image;
                                       }
                                       completion:NULL];
                   }
                   failure:NULL];

<小时>

更新:

顺便说一句，如果您担心图像视图(如果您引用 self，也包括视图或视图控制器)会一直保留到下载完成，你可以:

By the way, if you're concerned about the fact that the image view (and if you refer to self, the view or the view controller, too) being retained until the download is done, you could:

__weak UIImageView *weakImageView = self.imageView;
[imageView setImageWithURL:[NSURL URLWithString:@"http://i.imgur.com/r4uwx.jpg"] 
          placeholderImage:[UIImage imageNamed:@"placeholder-avatar"]
                   success:^(NSURLRequest *request, NSHTTPURLResponse *response, UIImage *image) {
                       UIImageView *strongImageView = weakImageView; // make local strong reference to protect against race conditions
                       if (!strongImageView) return;

                       [UIView transitionWithView:strongImageView
                                         duration:0.3
                                          options:UIViewAnimationOptionTransitionCrossDissolve
                                       animations:^{
                                           strongImageView.image = image;
                                       }
                                       completion:NULL];
                   }
                   failure:NULL];

即使你这样做了，图像视图也会一直保留到下载完成，因此你也可以选择在视图控制器的 dealloc 方法中取消任何正在进行的下载:

Even if you do that, the image view is retained until the download completes, so you could optionally also cancel any download in progress in the dealloc method of the view controller:

- (void)dealloc
{
    // if MRC, call [super dealloc], too

    [_imageView cancelImageRequestOperation];
}

这篇关于UIImageView+AFNetworking setImageWithURL 带动画的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持编程学习网！