UITableView crashes on scroll (memory warnings) - ios

Question

I have made my first UITableView, but when the number of cells is higher than what can be shown on the screen, and I scroll, it then crashes because of lack of memory.
I implemented the SDWEBIMAGE library to load the pictures async. and cache the images afterwards.
If more code is needed, please let me know !
I am a complete newbie at this, so please be gentle :)
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath{
static NSString *myIdentifier = #"defaultcell";
UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:myIdentifier forIndexPath:indexPath];
if(cell == nil){
cell = [[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:myIdentifier];
}
UIActivityIndicatorView *spinner = [[UIActivityIndicatorView alloc] initWithActivityIndicatorStyle: UIActivityIndicatorViewStyleWhiteLarge];
spinner.center = CGPointMake(160, 47);
[spinner startAnimating];
[cell.contentView addSubview:spinner];
//hide labels until done loading
cell.textLabel.hidden = YES;
cell.detailTextLabel.hidden = YES;
cell.imageView.hidden = YES;
UIImageView *iv = [[UIImageView alloc] initWithFrame:(CGRect){.size={80, 60}}];
iv.contentMode = UIViewContentModeScaleAspectFill;
iv.clipsToBounds = YES;
iv.frame = CGRectMake(15, 17, 80, 60);
NSString *profilePicName = [NSString stringWithFormat:#"%#%#", [self.dbhandler getPicturesPath], [[gallery objectAtIndex:indexPath.row] valueForKey: #"filename"]];
[iv setImageWithURL:[NSURL URLWithString:profilePicName] placeholderImage:[UIImage imageNamed:#"placeholder.png"] completed:^(UIImage *image, NSError *error, SDImageCacheType cacheType){
[spinner stopAnimating];
cell.textLabel.hidden = NO;
cell.detailTextLabel.hidden = NO;
cell.imageView.hidden = NO;
[cell.contentView addSubview:iv];
}];
NSString *subtitle = [NSString stringWithFormat:#"Comments: %# \nPosted: %#", [[gallery objectAtIndex:indexPath.row] valueForKey:#"comments"], [[gallery objectAtIndex:indexPath.row] valueForKey:#"created_at"]];
cell.detailTextLabel.numberOfLines = 0;
cell.textLabel.text = [NSString stringWithFormat:#"Votes: %#",[[gallery objectAtIndex:indexPath.row] valueForKey:#"votes"]];
cell.detailTextLabel.text = subtitle;
return cell;
}
UPDATED FUNCTION:
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath{
static NSString *myIdentifier = #"defaultcell";
UIActivityIndicatorView *spinner;
UIImageView *iv;
UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:myIdentifier forIndexPath:indexPath];
if(cell == nil){
cell = [[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:myIdentifier];
//build spinner
spinner = [[UIActivityIndicatorView alloc] initWithActivityIndicatorStyle: UIActivityIndicatorViewStyleWhiteLarge];
spinner.center = CGPointMake(160, 47);
spinner.tag = 101;
[cell.contentView addSubview:spinner];
//build ImageView
iv = [[UIImageView alloc] initWithFrame:(CGRect){.size={80, 60}}];
iv.contentMode = UIViewContentModeScaleAspectFill;
iv.clipsToBounds = YES;
iv.tag = 102;
iv.frame = CGRectMake(15, 17, 80, 60);
[cell.contentView addSubview:iv];
} else {
spinner = (UIActivityIndicatorView*)[cell viewWithTag:101];
iv = (UIImageView*)[cell viewWithTag:102];
}
[spinner startAnimating];
//the rest goes here
cell.textLabel.hidden = YES;
cell.detailTextLabel.hidden = YES;
cell.imageView.hidden = YES;
NSString *profilePicName = [NSString stringWithFormat:#"%#%#", [self.dbhandler getPicturesPath], [[gallery objectAtIndex:indexPath.row] valueForKey: #"filename"]];
NSLog(#"%#", profilePicName);
[iv setImageWithURL:[NSURL URLWithString:profilePicName] placeholderImage:[UIImage imageNamed:#"placeholder.png"] completed:^(UIImage *image, NSError *error, SDImageCacheType cacheType){
[spinner stopAnimating];
cell.textLabel.hidden = NO;
cell.detailTextLabel.hidden = NO;
cell.imageView.hidden = NO;
NSLog(#"done");
[cell.contentView addSubview:(UIImageView *)[cell viewWithTag:102]];
}];
NSString *subtitle = [NSString stringWithFormat:#"Comments: %# \nPosted: %#", [[gallery objectAtIndex:indexPath.row] valueForKey:#"comments"], [[gallery objectAtIndex:indexPath.row] valueForKey:#"created_at"]];
cell.detailTextLabel.numberOfLines = 0;
cell.textLabel.text = [NSString stringWithFormat:#"Votes: %#",[[gallery objectAtIndex:indexPath.row] valueForKey:#"votes"]];
cell.detailTextLabel.text = subtitle;
return cell;
}

Answer 1

Every-time you reuse a cell you are adding the UIActivityIndicatorView/spinner and UIImageView/iv as subviews. Better approach is to use a custom Prototype cell in the storyboard or reuse existing views by setting a Tag.
UIActivityIndicatorView *spinner;
UIImageView *iv;
if(cell == nil){
cell = [[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:myIdentifier];
//build spinner
spinner = [[UIActivityIndicatorView alloc] initWithActivityIndicatorStyle: UIActivityIndicatorViewStyleWhiteLarge];
spinner.center = CGPointMake(160, 47);
spinner.tag = 101;
[cell.contentView addSubview:spinner];
//build ImageView
iv = [[UIImageView alloc] initWithFrame:(CGRect){.size={80, 60}}];
iv.contentMode = UIViewContentModeScaleAspectFill;
iv.clipsToBounds = YES;
iv.tag = 102;
iv.frame = CGRectMake(15, 17, 80, 60);
[cell.contentView addSubview:iv];
} else {
spinner = (UIActivityIndicatorView*)[cell.contentView viewWithTag:101];
iv = (UIImageView*)[cell.contentView viewWithTag:102];
}
[spinner startAnimating];
//the rest goes here
You need to remove other addSubView calls(specifically in the callback block).
This should help you to get started.