In order to fluently download and display images in my UITableViewCell, I have implemented the following:
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath {
static NSString *CellIdentifier = @"Cell";
UITableViewCell *thisCell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier];
if (_movieCell == nil) {
thisCell = [[UITableViewCell alloc] initWithStyle:UITableViewCellStyleSubtitle reuseIdentifier:CellIdentifier];
}
Movie* thisMovie = [_movies objectAtIndex:indexPath.row];
thisCell.imageView.image = nil;
thisCell.textLabel.text =thisMovie.Title;
thisCell.imageView.image=[UIImage imageNamed:@"Dummy"];
thisCell.detailTextLabel.text = thisMovie.Year;
NSURL * imageURL = [NSURL URLWithString:[thisMovie.Poster stringByAddingPercentEscapesUsingEncoding:NSUTF8StringEncoding]];
NSURLSessionTask *task = [[NSURLSession sharedSession] dataTaskWithURL:imageURL completionHandler:^(NSData * _Nullable data, NSURLResponse * _Nullable response, NSError * _Nullable error) {
if (data) {
UIImage *image = [UIImage imageWithData:data];
if (image) {
dispatch_async(dispatch_get_main_queue(), ^{
UITableViewCell *updateCell = (id)[tableView cellForRowAtIndexPath:indexPath];
if (updateCell)
updateCell.imageView.image = image;
//[updateCell setNeedsLayout];
});
}
}
}];
[task resume];
return thisCell;
}
That all works very well, except for the fact, that after a few second of at least the execution of the visible part of the code, the debug console tells me
This application is modifying the autolayout engine from a background thread after the engine was accessed from the main thread.
This is part of a really simple app, that doesn't have any other background stuff going on, so I think it is this part of the code that is causing this issue.
Can anyone show me the mistake in my code, or, alternatively, explain a way to debug/track background threads?
Thanks ahead!
