TableView Slow Scroll - ios

Question

I'm developing and iOS app and my UITableView is kinda slow. I would like to know all the possible reasons for a slow scroll.
Note that I'm using prototype cells in the storyboard and I don't have any images.
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath {
static NSString *identifier = #"Cell";
UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:identifier];
if (cell == nil)
cell = [[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:identifier];
Classification *classification = [classifications objectAtIndex:indexPath.row];
UILabel *teamLabel = (UILabel *) [cell viewWithTag:101];
[teamLabel setText:[classification team]];
[cell setBackgroundColor:[UIColor clearColor]];
return cell;
}
Also, it runs smoothly in the simulator.
I'm using an iPad 2.

Answer 1

Download the data asynchronously in your:
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath {
Use 2 separated UITableViewCell objects, one to fill with text data, one for images which need to be in thread such as dispatch_async, example from my project:
if (imageUrl.length > 0)
{
NSString *completeURL = #"";
completeURL = [completeURL stringByAppendingString:kPROFILE_IMAGE_URL];
completeURL = [completeURL stringByAppendingString:#"/2/"];
completeURL = [completeURL stringByAppendingString:imageUrl];
completeURL = [completeURL stringByAppendingString:#".png"];
NSString *fileName = [NSString stringWithFormat:#"%#.png", imageUrl];
NSString* path = GetMediaFolder();
BOOL imageExists = [[NSFileManager defaultManager] fileExistsAtPath:[path stringByAppendingPathComponent:fileName]];
if (imageExists)
{
// NSLog(#"Image exists");
// Update UI
dispatch_async(dispatch_get_main_queue(), ^
{
UITableViewCell *updateCell = (id)[tableView cellForRowAtIndexPath:indexPath];
UIImageView *imageView = (UIImageView*)[updateCell viewWithTag:kTAG_IMAGE];
imageView.image=[UIImage imageWithContentsOfFile:[path stringByAppendingPathComponent:fileName]];
imageView.layer.cornerRadius = 23.0;
imageView.layer.borderColor = (__bridge CGColorRef)([UIColor clearColor]);
imageView.layer.borderWidth = 1.0;
imageView.clipsToBounds = YES;
imageView.contentMode = UIViewContentModeScaleAspectFill;
[updateCell setNeedsLayout];
});
}
else
{
// NSLog(#"Image not exists");
// Download The Image
dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^
{
NSURL *imageURL=[NSURL URLWithString:completeURL];
NSData *image=[NSData dataWithContentsOfURL:imageURL];
[image writeToFile:[path stringByAppendingPathComponent:fileName] atomically:YES];
// Update UI
dispatch_async(dispatch_get_main_queue(), ^
{
UITableViewCell *updateCell = (id)[tableView cellForRowAtIndexPath:indexPath];
UIImageView *imageView = (UIImageView*)[updateCell viewWithTag:kTAG_IMAGE];
imageView.image=[UIImage imageWithContentsOfFile:[path stringByAppendingPathComponent:fileName]];
imageView.layer.cornerRadius = 23.0;
imageView.layer.borderColor = (__bridge CGColorRef)([UIColor clearColor]);
imageView.layer.borderWidth = 1.0;
imageView.clipsToBounds = YES;
imageView.contentMode = UIViewContentModeScaleAspectFill;
[updateCell setNeedsLayout];
});
});
}
}
}
return cell;
EDIT 1:
I see you don't use images, you still need to download all the data asynchronously and fill it in the new UITableViewCell when download finished (instead of my images downloads, temporary data and downloaded data).