ios - AFNetworking:使用setImageWithURLRequest异步图片下载

Question

我有一个图像 slider ，正在使用 setImageWithURLRequest 从 url 下载图像。假设用户在应用程序代码后立即从左向右滑动，然后我必须显示我可以实现的最右边的索引图像，但之后我必须从索引的开头下载图像。如何实现？

for (int i = 0; i < self.items.count; i++) {
    CGRect frame;
    frame.origin.x = scrollView.frame.size.width * i;
    frame.origin.y = 0;
    frame.size = scrollView.frame.size;
    UIView *subview = self.view;

    UIImageView *imageView = [[UIImageView alloc] initWithFrame:frame];
    imageView.contentMode = UIViewContentModeCenter;
    subview = imageView;

    NSURLRequest *imagerequest = [NSURLRequest requestWithURL:[_items objectAtIndex:i]];
    __weak UIImageView *weakImageView = (UIImageView *) subview;

    [(UIImageView *) subview setImageWithURLRequest:imagerequest
                                placeholderImage:[UIImage imageNamed:@"placeholder.gif"]
                                         success:^(NSURLRequest *request, NSHTTPURLResponse *response, UIImage *image) {

                                             UIImageView *strongImageView = weakImageView; // make local strong reference to protect against race conditions
                                             if (!strongImageView) return;

                                             strongImageView.image = image;

                                         }
                                         failure:^(NSURLRequest *request, NSHTTPURLResponse *response, NSError *error) {
                                             //[activityIndicatorView removeFromSuperview];

                                             // do any other error handling you want here
                                         }];

    [scrollView addSubview:subview];
}

Answer 1

你可以使用UIImageView+AFNetworking.h:

- (void)setImageWithURL:(NSURL *)url
       placeholderImage:(UIImage *)placeholderImage;

例子:

[imageView setImageWithURL:<url> placeholderImage:<image>];

或者:

- (void)setImageWithURLRequest:(NSURLRequest *)urlRequest
              placeholderImage:(UIImage *)placeholderImage
                       success:(void (^)(NSURLRequest *request, NSHTTPURLResponse *response, UIImage *image))success
                       failure:(void (^)(NSURLRequest *request, NSHTTPURLResponse *response, NSError *error))failure;

例子:

[imageView setImageWithURL:<url> placeholderImage:<image> success:<successBlock> failure:<faliureBlock>];