不规则单元格图像-使用gcd下载图像并添加到NSMutable数组，然后在表视图单元格中显示

Question

我从链接下载图像并将其添加到NSMutableArray中。然后将其用作细胞图像。我从一个链接中获得一个图书列表，并过滤表中的内容，然后我有一个单独的链接，其中有相应的图像。带有优惠的第一个链接有一个图像路径，该路径被附加到一个链接以查找相应的图像。我正在使用grand-central dispatch来加载表视图中的图像。然而，这些图像并不总是与正确的书相对应。

这是cellForRowAtIndexPath:的问题代码

dispatch_queue_t queue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0);
dispatch_async(queue, ^{

 NSString * url = [NSString stringWithFormat:@"http://website/getBookImage.app?path=%@",[b.imgPath stringByAddingPercentEscapesUsingEncoding:NSUTF8StringEncoding]];
 NSURL * imageURL = [NSURL URLWithString:url];
 NSData * imageData = [NSData dataWithContentsOfURL:imageURL];
 UIImage * newImage = [UIImage imageWithData:imageData];
 UIImage * noPic = [UIImage imageNamed:@"noPic.jpg"];
 //resize the images
 CGRect rect = CGRectMake(0,0,111,115);
 UIGraphicsBeginImageContext( rect.size );
 [newImage drawInRect:rect];
 UIImage *picture1 = UIGraphicsGetImageFromCurrentImageContext();
 UIGraphicsEndImageContext();
 UIGraphicsBeginImageContext( rect.size );
 [noPic drawInRect:rect];
 UIImage * pic2 = UIGraphicsGetImageFromCurrentImageContext();
 UIGraphicsEndImageContext();
 NSData *imageData2 = UIImagePNGRepresentation(picture1);
 NSData * noPicData = UIImagePNGRepresentation(pic2);
 //if image is
    if (imageData.length == 0 ) {
        [self.merchantImage addObject:noPicData];
    }else{
        [self.merchantImage addObject:imageData2];
    }
 NSLog(@"image data %@",imageData);
    //call to main thread to tell it that its done
    //set cells
    dispatch_async(dispatch_get_main_queue(), ^{
        //set cells here
        //3.set the image cell
        imageSection.image = [UIImage imageWithData:[self.bookImage objectAtIndex:i];
        //tell cell to redraw
        i++;
        [cell setNeedsLayout];
    });
    // }
});

return cell;

我是一个相当新的，所以我很抱歉任何糟糕的编码。

Answer 1

您可以使用AFNetworking，它异步下载数据和图像，而且非常易于使用。

编辑：如何下载图像的示例

NSURL *URL = [NSString stringWithFormat:@"http://website/getBookImage.app?path=%@",[b.imgPath stringByAddingPercentEscapesUsingEncoding:NSUTF8StringEncoding]];
NSURLRequest *request = [NSURLRequest requestWithURL:URL];
AFHTTPRequestOperation *op = [[AFHTTPRequestOperation alloc] initWithRequest:request];
op.responseSerializer = [AFJSONResponseSerializer serializer];
[op setCompletionBlockWithSuccess:^(AFHTTPRequestOperation *operation, id responseObject) {
    NSLog(@"JSON: %@", responseObject);
    imageSection.image = responseObject;
} failure:^(AFHTTPRequestOperation *operation, NSError *error) {
    NSLog(@"Error: %@", error);
}];
[[NSOperationQueue mainQueue] addOperation:op];