Images in UITableView keep re-loading and wrong images flash while scrolling

Question

i have created a UITableView which populates each cell from URL requests. I have used \'dispatch_queue\' to prevent the UItableView from freezing. For some reason when i s

Answer 1

How you said. You catch the image in another thread, in order to prevent freezing. And in a tableView the cells are reused, and while in one background thread you are catching the new photo, in the main thread the cell with the previous photo is returned. Here in the code I fix it and better explanation:

customCell.customCellTextLabel.text = [NSString stringWithFormat:@"%@",feedO.title];

NSString *string = [NSString stringWithFormat:@"%@",feedO.body];

NSURL *urlString;

    NSDataDetector *linkDetector = [NSDataDetector dataDetectorWithTypes:NSTextCheckingTypeLink error:nil];
    NSArray *matches = [linkDetector matchesInString:string options:0 range:NSMakeRange(0, [string length])];
    for (NSTextCheckingResult *match in matches) {
        if ([match resultType] == NSTextCheckingTypeLink) {
            urlString = [match URL];
            NSLog(@"found Body URL: %@ and title %@", urlString,feedO.title);
        }
    }
   // Here you need, at least quit the previous imagen, is better if you implement
   //   and activity indicator (here start), and also you should implement some imagen cache.
   customCell.customCellImageView.image = nil;


   // Apart from here, go to another thread.

    dispatch_queue_t imageQueue = dispatch_queue_create("imageDownloader",nil);
    dispatch_async(imageQueue, ^{

        // this operation is slowly that return a cell, this happens after [1]
        NSData *data = [[NSData alloc] initWithContentsOfURL:urlString];

        dispatch_async(dispatch_get_main_queue(), ^{

        //If you implement and activity indicator stop here.
            customCell.customCellImageView.image = [UIImage imageWithData: data];
        });
    });

// [1] the cell is returned before the image is ready.
return customCell;