UIImageView + AFNetworking setImageWithURL带动画

时间:2013-07-18 17:23:44

标签: objective-c uiimageview afnetworking

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

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

如果我想用效果(可能是淡入淡出)替换图像怎么样?

这是因为我想用很多图片制作幻灯片。

2 个答案:

答案 0 :(得分:45)

您可以将animateWithDuration与提供setImageWithURL块的success的再现结合使用,例如

[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,如果占位符图片不是空白,您可能希望通过transitionWithView进行解散:

[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];

更新

顺便说一句,如果您担心图像视图(如果您引用self,视图或视图控制器)被保留直到下载完成,您可以:

__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];

即使您这样做,图像视图也会保留,直到下载完成,因此您也可以选择取消视图控制器的dealloc方法中正在进行的任何下载:

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

    [_imageView cancelImageRequestOperation];
}

答案 1 :(得分:3)

当在线请求成功完成时,尝试将imageView的alpha设置为0到1的动画:

// You should not call an ivar from a block (so get a weak reference to the imageView)
__weak UIImageView *weakImageView = self.imageView;

// The AFNetworking method to call
[imageView setImageWithURLRequest:[NSURLRequest requestWithURL:[NSURL URLWithString:@"http://host.com/image1.png"]] placeholderImage:nil] 
                   success:^(NSURLRequest *request, NSHTTPURLResponse *response, UIImage *image){ 
                     // Here you can animate the alpha of the imageview from 0.0 to 1.0 in 0.3 seconds
                     [weakImageView setAlpha:0.0];
                     [UIView beginAnimations:nil context:NULL];
                     [UIView setAnimationDuration:0.3];
                     [weakImageView setAlpha:1.0];
                     [UIView commitAnimations];
                   }
                   failure:^(NSURLRequest *request, NSHTTPURLResponse *response, NSError *error){
                     // Your failure handle code     
                   }

当然,您可以在完成区内使用您喜欢的任何其他动画!