prevent UILabel repeat added to custom UITableViewCell - ios

Question

I have a customCell and I need to add more than one UILabel as "tag" to each cell,
My code is like this:
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath {
static NSString *ID = #"topicCell";
MSPTopicCell *cell = [tableView dequeueReusableCellWithIdentifier:ID];
NSArray *labelArray = [TopicLabelArr objectAt:index.row];
for (int i = 0; i < [labelArray count]; i++) {
UILabel *tmpLabel = [UILabel alloc]initwithFrame .....];
tmpLabel.text = [labelArray objectAt:i];
[cell.view addSubview:tmpLabel];
}
return cell;
}
I use Xib to create the custom cell.
What I need is make the for-loop only execute one time on each cell.
However, there are many rows in tableView, and the labels will be created repeatly every times when I scroll up and down. How to improve it? Any idea? Thanks.

Answer 1

When you use dequeueReusableCellWithIdentifier, you are not creating a new MSPTopicCell you (as the name of the method says) reuse a cell.
What does that mean ? You obviously need at least as many cell as how much you are displaying at the same time, but once your start scrolling, the cells which disappear of your scrollview are reused.
The labels you add to the subview are added overtime, even on a reused cell which already got some subviews added, which produce your issue.
There are many ways to fix it, here are some examples:
You can remove the subviews added before adding new ones. Add the following line before your for loop using the following code:
view.subviews.forEach({ $0.removeFromSuperview() }
Use a custom tag for your labels so you can see it they already exist or not :
for (int i = 0; i < [labelArray count]; i++) {
UILabel *tmpLabel = (UILabel *)[self viewWithTag:100+i];
if (tmpLabel == nil)
{
tmpLabel = [UILabel alloc]initwithFrame .....];
tmpLabel.tag = 100 + i;
[cell.view addSubview:tmpLabel];
}
tmpLabel.text = [labelArray objectAt:i];
}
The best solution, in my opinion, since you already use an UITableViewCell subclass : simply directly add some UILabel properties on your MSPTopicCell class, so you don't have to create it in cellForRowAtIndexPath. But maybe this case is not adapted for you since the number of labels depend of the labelArray, which dependents of the position of the cell.

Answer 2

You can create a UIView which will include all your UILabel. However when you reuse the cell at the beginning just remove that view from superview.
So masterview will be removed from your cell.
i.e
[[cell.contentView viewWithTag:101] removeFromSuperview]
UIView *yourViewName = [[UIView alloc]init];
// set your view's frame based on cell.
yourViewName.tag = 101;
for (int i = 0; i < [labelArray count]; i++) {
UILabel tmpLabel = (UILabel )[self viewWithTag:100+i];
if (tmpLabel == nil)
{
tmpLabel = [UILabel alloc]initwithFrame .....];
tmpLabel.tag = 100 + i;
[yourViewName addSubview:tmpLabel];
}
tmpLabel.text = [labelArray objectAt:i];
}
[cell.contentView addSubView:yourViewName];
This process will speed up your cell's scrolling performance as well.
Hope this answer helped you.