2 starwar2012 starwar2012 于 2013.02.20 09:45 提问

AFImageRequestOperation返回图片

要写一个应用,用来接受图片标示符,并且使用 AFNetworkingAFImageRequestOperation 下载图片。

目前下载已经成功了,但是在block中无法返回UIImage。

-(UIImage *)downloadImage:(NSString*)imageIdentifier
{
  NSString* urlString = [NSString stringWithFormat:@"http://myserver.com/images/%@", imageIdentifier];

  AFImageRequestOperation* operation = [AFImageRequestOperation imageRequestOperationWithRequest:[NSURLRequest requestWithURL:[NSURL URLWithString:urlString]] imageProcessingBlock:nil
  success:^(NSURLRequest *request, NSHTTPURLResponse *response, UIImage *image)
  {
    NSLog(@"response: %@", response);
    return image;                                                   
  }
  failure:nil];

[operation start];

}

其中return image;这行报错:

Incompatible block pointer types sending 'UIImage *(^)(NSURLRequest *__strong, NSHTTPURLResponse *__strong, UIImage *__strong)' to parameter of type 'void (^)(NSURLRequest *__strong, NSHTTPURLResponse *__strong, UIImage *__strong)' 

我希望能调用:

UIImage* photo = [downloadImage:id_12345];

1个回答

redCoral_
redCoral_   2013.02.20 11:22
已采纳

AFNetworking图片下载操作是异步的,你不能在操作开始的时候指定它。

你构建的函数应该用delegates和block。

- (void)downloadImageWithCompletionBlock:(void (^)(UIImage *downloadedImage))completionBlock identifier:(NSString *)identifier {
  NSString* urlString = [NSString stringWithFormat:@"http://myserver.com/images/%@", identifier];

  AFImageRequestOperation* operation = [AFImageRequestOperation imageRequestOperationWithRequest:[NSURLRequest requestWithURL:[NSURL URLWithString:urlString]] imageProcessingBlock:nil
  success:^(NSURLRequest *request, NSHTTPURLResponse *response, UIImage *image)
  {
    NSLog(@"response: %@", response);
    completionBlock(image);                                                   
  }
  failure:nil];

  [operation start];
}

如下调用:

// start updating download progress UI
[serverInstance downloadImageWithCompletionBlock:^(UIImage *downloadedImage) {
  myImage = downloadedImage;
  // stop updating download progress UI
} identifier:@""];
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