Question

I have a UITableView and a UITableCell subclass. Each table cell has two scrollviews that each rotate a dynamic amount of labels, which are created in my table cell implementation. I have poor scrolling performance and I believe it is from memory leaks. I’m referencing this stackoverflow correct answer to fix my problem: cellForRowAtIndexPath memory management.

I can’t figure out how to tweak my code so I don’t have to allocate memory every time I create labels.

ViewController.m

- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
static NSString *CellIdentifier = @"Custom Cell";

cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier];
if (cell == nil) {
    cell = [[CustomCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:CellIdentifier];
}


NSDictionary *dictionary = [parseDataArray objectAtIndex: indexPath.row];

NSArray *popularLinkTitleArray = [dictionary objectForKey:@"popularLinkTitleArray"];
NSString *soundCloudLink = [dictionary objectForKey:@"soundCloudLink"];
NSArray *soundCloudTrackTitleArray = [dictionary objectForKey:@"soundCloudTrackTitleArray"];


cell.artistNameLabel.text = artistName;

[cell createPopularLinkLabels: popularLinkTitleArray];

return cell;
}

CustomCell.m

- (void)layoutScrollLabelsForPopularLinkScrollView: (float)arrayCount
{
UIView *view = nil;
NSArray *subviews = [popularLinkScrollView subviews];

// reposition all image subviews in a horizontal serial fashion
CGFloat curXLoc = 0;
for (view in subviews)
{
    if ([view isKindOfClass:[UILabel class]] && view.tag >= 0)
    {
        CGRect frame = view.frame;
        frame.origin = CGPointMake(curXLoc, 0);
        view.frame = frame;

        curXLoc += (kScrollObjWidth);
    }
}

[popularLinkScrollView setContentSize:CGSizeMake((arrayCount * kScrollObjWidth),    [popularLinkScrollView bounds].size.height)];

}

-(void) createPopularLinkLabels:(NSArray *) popularLinkTitleArray
{

popularLinkScrollView.clipsToBounds = YES;

kScrollObjHeight = popularLinkScrollView.frame.size.height;
kScrollObjWidth = popularLinkScrollView.frame.size.width;

for (UIView* subView in popularLinkScrollView.subviews)
    [subView removeFromSuperview];

NSUInteger i;
    for (i = 0; i < popularLinkTitleArray.count; i++)
    {
        NSString *string = [NSString stringWithFormat:@"%@", [popularLinkTitleArray objectAtIndex: i]];
        UILabel *label = [[UILabel alloc] init];
        label.text = [NSString stringWithFormat:@"%@", string];
        label.backgroundColor = [UIColor clearColor];
        label.numberOfLines = 5;
        [label setFont:[UIFont fontWithName:@"Calibri" size:18]];

        // setup each frame to a default height and width, it will be properly placed when we call "updateScrollList"
        CGRect rect = label.frame;
        rect.size.height = kScrollObjHeight;
        rect.size.width = kScrollObjWidth;
        label.frame = rect;
        label.tag = i;  // tag our images for later use when we place them in serial fashion
        [popularLinkScrollView addSubview:label];
    }

[self layoutScrollLabelsForPopularLinkScrollView:popularLinkTitleArray.count];

}

Answer 1

The first thing you could do is try to reuse UILabels in createPopularLinkLabels. Right now, you are just removing them before adding more.

But if the number of popular links is not the same in all the cells, then you will have to remove the remaining ones or hide them and there will be no way to avoid memory allocations.

A better solution would be to insert a custom UIView inside your scroll view and draw all the texts manually instead of creating tons of subviews.

Hope this helps,
Thomas