Question

我有一个应用程序，你可以拍照，一旦它被拍摄它会自动上传到服务器，生成这张照片的拇指。拍照后，我的应用程序返回到UICollectionView。问题有时候，最后一张图片不会加载拇指，我只有占位符而不是实际图片的拇指。我需要重新加载视图或滚动才能看到它。

这是我的加载功能：

    - (void)setCellPhotos:(UIImageView *)avatar avatarUrl:(NSString *)avatarUrl
{
    UIApplication* app = [UIApplication sharedApplication];
    app.networkActivityIndicatorVisible = YES;

    NSURL *url = [NSURL URLWithString:avatarUrl];
    NSURLRequest *request = [NSURLRequest requestWithURL:url];
    UIImage *img = [UIImage imageNamed:@"square"];
    __weak UIImageView *avatarView = avatar;
    [avatarView setImageWithURLRequest:request
                      placeholderImage:img
                               success:^(NSURLRequest *request, NSHTTPURLResponse *response,
                                         UIImage *image)
     {
         avatarView.image = image;
         UIApplication* app = [UIApplication sharedApplication];
         app.networkActivityIndicatorVisible = NO;

     }failure:^(NSURLRequest *request, NSHTTPURLResponse *response, NSError *error)
    {
        UIApplication* app = [UIApplication sharedApplication];
        app.networkActivityIndicatorVisible = NO;
    }];
}

我的细胞功能：

- (UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath {
    UICollectionViewCell *cell = [collectionView dequeueReusableCellWithReuseIdentifier:reuseIdentifier forIndexPath:indexPath];

    NSDictionary *pic = [photosArray objectAtIndex:indexPath.row];
    UIImageView *picImageView = (UIImageView *)[cell viewWithTag:100];

    [self setCellPhotos:picImageView avatarUrl:[pic objectForKey:@"thumb"]];

    return cell;
}

我还有一个代表，在完成图片上传后返回给我，然后我请求获取新图库后跟一个：

[self.collectionView reloadData];

我检查了服务器端，并在向我发送回复之前生成了拇指。

感谢您的帮助

Answer 1

您的问题是来自NURLRequest的响应发生在后台线程上，并且所有UI更新都需要在主线程上。如果你等待足够长的时间，你可能会发现图片最终会显示出来。

要解决此问题，只需修改返回块以包括在主线程上设置图像，例如;

 - (void)setCellPhotos:(UIImageView *)avatar avatarUrl:(NSString *)avatarUrl
 {
     UIApplication* app = [UIApplication sharedApplication];
     app.networkActivityIndicatorVisible = YES;

     NSURL *url = [NSURL URLWithString:avatarUrl];
     NSURLRequest *request = [NSURLRequest requestWithURL:url];
     UIImage *img = [UIImage imageNamed:@"square"];
     __weak UIImageView *avatarView = avatar;
     [avatarView setImageWithURLRequest:request
                  placeholderImage:img
                           success:^(NSURLRequest *request, NSHTTPURLResponse *response,
                                     UIImage *image)
     {
           dispatch_async(dispatch_get_main_queue(), ^{
             avatarView.image = image;
             UIApplication* app = [UIApplication sharedApplication];
             app.networkActivityIndicatorVisible = NO;
            });

      }failure:^(NSURLRequest *request, NSHTTPURLRes ponse *response, NSError *error)
      {
          UIApplication* app = [UIApplication sharedApplication];
          app.networkActivityIndicatorVisible = NO;
  }];
 }

您可能还应修改故障块

UICollectionView和AFNetworking图像有时无法加载

1 个答案: