How to keep the didSelect action in UICollectionView in Objective-c? - ios

Question

I have a UICollectionView and I add from my cellForItemAtIndexPath 12 cells. When I do scroll on this to see down cells, all functions is preserved, but when I do scroll to go up again, some cells don't execute the function loaded in didSelectItemAtIndexPath.
I set disabled some rows. But not the row that I clicked Why could be this? Could be a bad prepare for reuse cell?
I'm trying the reuse function, but this only affect drawing the cell wrong or on the another position and the function added in didSelectItemAtIndexPath not work:
[self.myCollectionView reloadData];
[self.myCollectionView layoutIfNeeded];
NSArray *visibleItems = [self.myCollectionView indexPathsForVisibleItems];
NSIndexPath *currentItem = [visibleItems objectAtIndex:0];
NSIndexPath *nextItem = [NSIndexPath indexPathForItem:currentItem.item + 1 inSection:currentItem.section];
[self.myCollectionView scrollToItemAtIndexPath:nextItem atScrollPosition:UICollectionViewScrollPositionTop animated:YES];
WHen I do scroll and the do click to one cell, this not open my secondViewController, I think that this cell is gettin a wrong index that was disabled.
- (UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath
{
MyViewController *cell = [collectionView dequeueReusableCellWithReuseIdentifier:#"myCell" forIndexPath:indexPath];
switch ([indexPath row]) {
case 0:
titleCell= #"Title0";
detailCell=#"Detail0";
if([indexPath row]==2){
[cell setUserInteractionEnabled:NO];//Here I set disable Could be the problem caused by this??
}
[cell.image setHidden:YES];
cell.image.contentMode = UIViewContentModeScaleAspectFit;
break;
//Here other cases with the same structure
return cell;
}
- (void)collectionView:(UICollectionView *)collectionView didSelectItemAtIndexPath:(NSIndexPath *)indexPath
{
[collectionView deselectItemAtIndexPath:indexPath animated:NO];
MySecondClass *secondClass = [self.storyboard instantiateViewControllerWithIdentifier:#"myVC"];
[self.navigationController pushViewController:secondClass animated:YES];
}
-(void)collectionView:(UICollectionView *)collectionView willDisplayCell:(UICollectionViewCell *)cell forItemAtIndexPath:(NSIndexPath *)indexPath
{
//Here assign yellow background color to first row and white color to the second row
}
And in my cell class I added the prepareForReuse but this not work...
- (void)prepareForReuse {
[super prepareForReuse];
[self removeFromSuperview];
[self setNeedsLayout];
}

Answer 1

The problem lies on this piece of code:
- (UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath
{
MyViewController *cell = [collectionView dequeueReusableCellWithReuseIdentifier:#"myCell" forIndexPath:indexPath];
switch ([indexPath row]) {
case 0:
titleCell= #"Title0";
detailCell=#"Detail0";
if([indexPath row]==2){
[cell setUserInteractionEnabled:NO];//Here I set disable Could be the problem caused by this??
}
[cell.image setHidden:YES];
cell.image.contentMode = UIViewContentModeScaleAspectFit;
break;
return cell;
}
Because cells are reusable. So the cell that you disabled earlier (For example cell0) will continue to be reused. When you scroll, that cell0 will become cell11 for example. However, its setting is still disabled.
You need to add a else statement to remove the disabled setting like this.
if([indexPath row]==2){
[cell setUserInteractionEnabled:NO];//Here I set disable Could be the problem caused by this??
}
else{
[cell setUserInteractionEnabled:YES];
}

Answer 2

When a cell scrolls off the screen it is potentially deallocated or (more likely) recycled, so any state you have in that cell is not persisted once its off screen. The solution is that you should check if a cell is selected and update its appearance in cellForRowAtIndexPath. You can just have didSelectItemAtIndexPath and didDeselectItemAtIndexPath call reloadRowsAtIndexPath and cellForRowAtIndexPath will handle all of the highlighting appearance logic in one place.