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Web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UIImageView 规模调整图像.

知道怎么做吗？

编辑

我正在使用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

我解决了设置UIImageView的问题

self.contentMode = UIViewContentModeScaleAspectFill;

self.clipsToBounds = YES;

基本上这设置图像具有适当的比例,并切割所有边缘..

Answer 1

AF UIImageView类别的变体在异步图像请求完成时调用块.

您可以在成功块中调整返回的图像的大小,并将其指定给图像视图.看到

- (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UIImageView使用GCD 将图像分配给主队列,因为将在后台线程中调用块.

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调整大小通常比使用UIImageView重新调整图像质量更好.

__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
}];