ios - 使用 AFNetworking 在异步模式下调整 UIImage 的大小

Question

我在我的应用程序中使用 AFNetwork 从我的网络服务中获取一些数据。在这些数据中，有一些随机大小的图像，我需要添加一些 UIImageView。

我的问题是在异步模式下以正确的比例调整图像 UIImageView。

知道怎么做吗？

编辑

我使用的是 Afnetwoking 项目的常规方法:

 [self setImageWithURL:[NSURL URLWithString:url] placeholderImage:[UIImage imageNamed:@"img_my_nophoto"]];

这个方法里面的逻辑是:

- (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
{
    [self cancelImageRequestOperation];

UIImage *cachedImage = [[[self class] af_sharedImageCache] cachedImageForRequest:urlRequest];
if (cachedImage) {
    self.image = cachedImage;
    self.af_imageRequestOperation = nil;

    if (success) {
        success(nil, nil, cachedImage);
    }
} else {
    self.image = placeholderImage;

    AFImageRequestOperation *requestOperation = [[AFImageRequestOperation alloc] initWithRequest:urlRequest];
    [requestOperation setCompletionBlockWithSuccess:^(AFHTTPRequestOperation *operation, id responseObject) {
        if ([[urlRequest URL] isEqual:[[self.af_imageRequestOperation request] URL]]) {
            self.image = responseObject;
            self.af_imageRequestOperation = nil;
        }

        if (success) {
            success(operation.request, operation.response, responseObject);
        }

        [[[self class] af_sharedImageCache] cacheImage:responseObject forRequest:urlRequest];


    } failure:^(AFHTTPRequestOperation *operation, NSError *error) {
        if ([[urlRequest URL] isEqual:[[self.af_imageRequestOperation request] URL]]) {
            self.af_imageRequestOperation = nil;
        }

        if (failure) {
            failure(operation.request, operation.response, error);
        }

    }];

    self.af_imageRequestOperation = requestOperation;

        [[[self class] af_sharedImageRequestOperationQueue] addOperation:self.af_imageRequestOperation];
    }
}

完整的类代码: https://github.com/AFNetworking/AFNetworking/blob/master/AFNetworking/UIImageView%2BAFNetworking.m

解决方案

我解决了设置 UIImageView 的问题

self.contentMode = UIViewContentModeScaleAspectFill;

self.clipsToBounds=YES;

基本上这会以适当的比例设置图像，并切割所有边缘..

Answer 1

AF UIImageView 类别有一个变体，它在异步图像请求完成时调用一个 block 。

您可以在成功 block 中调整返回图像的大小并将其分配给 ImageView 。见

- (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

调整图像大小后，请确保使用 GCD 将图像分配给主队列上的 UIImageView，因为该 block 将在后台线程中调用。

这是一个使用 UIIImageView 并将其内容模式设置为 AspectFill 的示例。使用 Core Graphics 调整大小通常比让 UIImageView 重新缩放图像看起来更好。

__weak typeof(self) weakSelf = self;
CGSize targetSize = self.targetImageView.bounds.size;
[self.targetImageView setImageWithURL:photoURL success:^(UIImage *image) {

    CGFloat imageHeight = image.size.height;
    CGFloat imageWidth = image.size.width;

    CGSize newSize = targetSize;
    CGFloat scaleFactor = targetSize.width / imageWidth;
    newSize.height = imageHeight * scaleFactor;

    UIGraphicsBeginImageContextWithOptions(newSize, NO, 0.0);
    [image drawInRect:CGRectMake(0, 0, newSize.width, newSize.height)];
    UIImage *small = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();
    dispatch_async(dispatch_get_main_queue(),^ {

        weakSelf.targetImageView.image = small;
    });

} failure:^(NSError *error) {
    // Handel the error here
}];