Question

I use the following code to trigger image downloads in visible cells/paths:

- (void)loadImagesForOnScreenrows {
   NSArray *visiblePaths = [tableView indexPathsForVisibleRows];

   for (NSIndexPath *indexPath in visiblePaths) {
      UITableViewCell *cell = [tableView cellForRowAtIndexPath:indexPath];
      if([cell viewWithTag:kTagImageView] != nil) {
         (ImageViewCached *)[[cell viewWithTag:kTagImageView] triggerDownload];
      }
   }
}


// Load images for all onscreen rows when scrolling is finished
- (void)scrollViewDidEndDragging:(UIScrollView *)scrollView willDecelerate:(BOOL)decelerate
{
   if (!decelerate)
    {   
        [self loadImagesForOnscreenRows];
    }

}

- (void)scrollViewDidEndDecelerating:(UIScrollView *)scrollView
{
    [self loadImagesForOnscreenRows];
}

However, apparently the indexPaths returned do not reflect the actual onscreen rows.

Especially if I scroll fast, the rows returned will be ones that are already off screen.

Can anyone think of a good (probably obvious) reason why that would be the case?

Answer 1

Is -loadImagesForOnscreenRows being called anywhere else?

It looks like you started from the LazyTableImages sample code. I could only get that sample project to invoke -loadImagesForOnscreenRows when scrolling ended (or at the end of a drag).

Scrolling fast was irrelevant in that project, since the visible rows aren’t asked for until scrolling stops.

I only tried the LazyTableImages code on the simulator, not a device. YMMV.