UICollectionView and Scrolling Program Bug

Question

I have a UICollectionView inside of a normal UIViewController.

Inside the collectionview I have designed the reusable UI for the collectionviewcells in storyboard.

Inside of the collectionviewcell there is a label that displays the cells indexpath.row and 5 UIButtons which if selected, change color and stay selected.

I have set up the collectionview so that if more that 30 cells are requested the collectionview will page horizontally, the collectionview layout is also horizontal.

The application runs nicely, scrolls properly and lays out cells correctly.

The problem I am having is when you select for example button A in cell 1 in the collectionviewcell (which is suppose to layout 100 cells) and page over two pages (60+ Cells) to page 3, button A in cell number 75 is selected. And further more if you scroll to the end (100 cells) and scroll back to page 3, button A in cell number 75 is on longer selected, but button A in cell number 64 is selected.

Here is some snippets of code: cell.m - controls the action from the user.

- (IBAction)bubbleButtons:(id)sender {
    for(UIButton *bubbleCell in self.bubbleButtons) {
            if (bubbleCell.touchInside && !bubbleCell.selected) {
                bubbleCell.selected = YES;
            } else if (bubbleCell.touchInside && bubbleCell.selected) {
                bubbleCell.selected = NO;
            }
      }

 }

MainViewContoller.m - sets up cell from UICollectionViewCell made in storyboard

-(UICollectionViewCell *)collectionView:(UICollectionView *)collectionView 
                 cellForItemAtIndexPath:(NSIndexPath *)indexPath {
        Cell *cell1;
        cell1 =[collectionView dequeueReusableCellWithReuseIdentifier:zCellID
                                                         forIndexPath:indexPath];
        cell1.numMainLabel.text = [NSString stringWithFormat:@"%d |",indexPath.row+1];
        return cell1;

I do not really understand what is wrong or what is causing this bug, I am assuming it has todo with the view being reloaded when a new part of the view becomes visible but that is just a guess. Help would be greatly appreciated.

Zach

Kyle Fang Kyle Fang · Accepted Answer · 2013-09-21T18:50:16

It's probably because the reusable view is reused.

The proper way to do this is to create custom reusable view subclass. And save the selection of those 5 button.

        cell1 =[collectionView dequeueReusableCellWithReuseIdentifier:zCellID

This line here might or might not give you a new cell, it might give you a cell that is used before. So, you need to update the selection in there. Or it stay the same as the cell it's reusing.

UICollectionView and Scrolling Program Bug

2 Answers