SDWebImage + UITableViewCell, wrong image when scrolling?

问题

i'm having an issue using SDWebImage to load images to a UIImageView inside a custom UITableViewCell. This is my code at the UITableView delegate:

    static NSString *userTableId = @"userTableId";
    UserDetailsTableViewCell *cell = (UserDetailsTableViewCell *)[tableView dequeueReusableCellWithIdentifier:userTableId];
    NSDictionary *user = [userList objectAtIndex:indexPath.row];
    NSInteger position = indexPath.row + 1;
    [cell.userDetailsView loadFromDictionary:user WithIndex:position ForCharitie:false];
        cell.userDetailsView.delegate = self;

    cell.userDetailsView.delegate = self;
    return cell;

And here is my code for loadFromDictionary:

-(void) loadFromDictionary: (NSDictionary *) dic  WithIndex: (NSInteger) index ForCharitie: (BOOL) isCharitie{
    NSDictionary *userImageDic = [dic objectForKey:@"image"];
    NSString *url =[userImageDic objectForKey:@"url"];

    [userImage setImage:[UIImage imageNamed:@"defaultAvatar"]];
    if ([url class] != [NSNull class]){
        [userImage setImageWithURL:[NSURL URLWithString:url] placeholderImage:[UIImage imageNamed:@"defaultAvatar"]];
    }
}

Now, the problem is if i scroll down before some images finish loading. For example, let's say I see the first 8 rows, and rows 1, 2 and 3 still loading their images, now i scroll to 9-16, i see the defaultAvatar for all of them, and after a few seconds (i guess when images of rows 1,2 and 3 finish downloading), the images on cells 9, 10 and 11 change to the ones that belong to 1,2 and 3. I don't know if there is a way to stop the images from downloading when i reuse the cell, or something like that. Thank you and sorry for my English!

回答1:

If you have your UITableViewDelegate set on your table, you could use the delegate method:

- tableView:didEndDisplayingCell:forRowAtIndexPath:

to set the image to NULL (or the default) when your cell scrolls off screen.

And since you're using SDWebImage, canceling it could be as easy as "cancelCurrentImageLoad" on the cell's image view.

回答2:

Override prepareForReuse method in your cell class and cancel all loadings there. Do not forget to call super

回答3:

Example of answer above. Swift 3

func collectionView(_ collectionView: UICollectionView, didEndDisplaying cell: UICollectionViewCell, forItemAt indexPath: IndexPath) {
    (cell as! UITableViewCell).imageView.image = nil
    (cell as! UITableViewCell).imageView.sd_cancelCurrentImageLoad()
}

回答4:

I was getting blank images with the accepted answer and given the images I'm loading are small, I wanted to let the images cache in the background and not cancel the load.

Push a unique id on the stack before your closure and check it when your closure completes
prepareForReuse

Like this:

func updateArtistImage(url: URL) {
        let _eventId = self.event?.id
        SDWebImageManager.shared().loadImage(with: url, options: [], progress: nil) { (image, data, error, cacheType, finished, url) in
            if self.event!.id == _eventId {
                if error == nil {
                    self.artistImageView.image = image
                } else {
                    self.artistImageView.image = UIImage(named: "error_image")
                }
            }
        }
    }

and this:

override func prepareForReuse() {
    super.prepareForReuse()
    self.artistImageView.image = nil
}

回答5:

Just call sd_cancelCurrentImageLoad and set [imageView setImage:nil] before call sd_setImageWithURL.

[imageView sd_cancelCurrentImageLoad];

来源：https://stackoverflow.com/questions/23741124/sdwebimage-uitableviewcell-wrong-image-when-scrolling

标签

ios

uitableview

sdwebimage