从网络的标题区域视图中加载UIImageView的图像

Question

I use UITableView and want to display UIImageView with loaded image from network in section header. So my method

- (UIView *)tableView:(UITableView *)tableView viewForHeaderInSection:(NSInteger)section returns next UIView :

    UIView * header = [UIView new];
    header.frame = CGRectMake(0, 0, self.view.frame.size.width, 200);
    header.backgroundColor = UIColor.clearColor;
    UserDataModel * userData = [CoreDataService sharedInstance].userData;
    UIImageView * userImageView = [UIImageView new];
    userImageView.frame = CGRectMake(20, 20, self.view.frame.size.width * 0.3, self.view.frame.size.width * 0.3);
    dispatch_async(dispatch_get_global_queue(0,0), ^{
        NSData * data = [[NSData alloc] initWithContentsOfURL: [NSURL URLWithString: userData.photoPath]];
        if (data == nil) {

            return;
        }
        dispatch_async(dispatch_get_main_queue(), ^{
            userImageView.image = [UIImage imageWithData: data];
        });
    });
    [header addSubview:userImageView];
    return header;

And it works only after scrolling table view, I can't figure out what I did wrong. Please explain me why it is wrong and how to do it correctly. Thanks.

Answer 1

Reload the UIImageView after adding the image.

 dispatch_async(dispatch_get_main_queue(), ^{
        userImageView.image = [UIImage imageWithData: data];
        [userImageView setNeedsDisplay];
    });

Answer 2

First use SDWebImage to download it once as your current code will download it every header appearance

Second create an array of models (imagesUrls) for all header then loop for urls

UIImageView*img = [UIImageView new];

for (int section = 0; section < [myArray count]; section++)
{
    MyModel *model = [myArray objectAtIndex:section];

    [img sd_setImageWithURL:[NSURL URLWithString:model.url] completed:^(UIImage * _Nullable image, NSError * _Nullable error, SDImageCacheType cacheType, NSURL * _Nullable imageURL) {

          [tableView reloadSections:[[NSIndexSet alloc] initWithIndex:section] withRowAnimation:NO];
     }];
}