AFNet工作异步下载GIF与占位符

Question

我一直在使用AFNetworking下载带有占位符的UIImage异步，它适用于JPEG和PNG，但是我正在使用一个库来播放我的GIF图片。当我同步运行时，它运行良好。但是，我想使用 AFNetworking 异步下载图像，同时在 ImageView 中显示占位符图像。我该怎么做？谢谢！

这是我的代码：

- (void) downloadAllImagesForComment
{
    if (_imageLinkList.count > 0)
    {
        if (images == nil)
            images = [[NSMutableDictionary alloc] init];
        for (NSDictionary *URL in _imageLinkList) {
            if ([images objectForKey:[URL objectForKey:@"link"]] == nil)
            {
                /*
                 * imageType = 0 <= other
                 * imageType = 1 <= gif
                 */
                int imageType = 0;
                NSURL *url = [NSURL URLWithString:[URL objectForKey:@"link"]];
                NSError *error = [[NSError alloc] init];
                NSLog(@"Retrieving imageData...");
                NSData *imageData = [NSData dataWithContentsOfURL:url options:NSDataReadingMappedIfSafe error:&error];
                NSLog(@"Retrived imageData.");
                uint8_t c;
                [imageData getBytes:&c length:1];
                switch (c) {
                    case 0xFF:
                        NSLog(@"image/jpeg");
                        imageType = 0;
                        break;
                    case 0x89:
                        NSLog(@"image/png");
                        imageType = 0;
                        break;
                    case 0x47:
                        NSLog(@"image/gif");
                        imageType = 1;
                        break;
                    case 0x49:
                        imageType = 0;
                        break;
                    case 0x4D:
                        NSLog(@"image/tiff");
                        imageType = 0;
                        break;
                }
                UIImageView *temp_imageView;
                if (imageType == 1)
                {
                // GIF IMAGE SHOULD BE INITIALIZED HERE!!!!!!
//                    image = [UIImage animatedImageWithAnimatedGIFData:imageData];
                }
                else
                {
                    temp_imageView = [[UIImageView alloc] initWithFrame:CGRectMake(0, 0, 280, 250)];
                    [temp_imageView setImageWithURL:url placeholderImage:[UIImage imageNamed:@"patch_la"]];
                }
                [images setValue:temp_imageView forKey:[URL objectForKey:@"link"]];
                NSLog(@"Done downloading image: %@", [URL objectForKey:@"link"]);
            }
        }
    }
}

Answer 1

我建议使用SDWebImage库。它具有内置的异步动画 Gif 支持。

包含库后，它很简单（只需将 NSURL 指向远程 Gif）：

[imageView setImageWithURL:[NSURL] completed:^(UIImage *image, NSError *error, SDImageCacheType cacheType){}];