viewForSupplementaryElementOfKind not working because of empty array - ios

Question

Sometimes (it does not occur everytime eventhough the data does not change), the headers/ footers in my uiCollectionView cannot be instantiated and the app crashes because I get the following error :
Terminating app due to uncaught exception 'NSRangeException', reason: '*** -[__NSArrayM objectAtIndex:]: index 0 beyond bounds for empty array'
I set the size of my footer to 0 when it is in a odd-numbered section.
- (UICollectionReusableView *)collectionView:(UICollectionView *)collectView viewForSupplementaryElementOfKind:(NSString *)kind atIndexPath:(NSIndexPath *)indexPath
{
UICollectionReusableView *view;
NSLog(#"indexpath section %ld", (long)indexPath.section);
if(kind == UICollectionElementKindSectionHeader){
HeaderViewQuestion *headerView = [collectView dequeueReusableSupplementaryViewOfKind:UICollectionElementKindSectionHeader withReuseIdentifier:#"HeaderViewQuestion" forIndexPath:indexPath];
NSString *initial = [[NSString alloc] initWithFormat:#"Question %d : ",(int)indexPath.section+1];
NSMutableString *text = [[NSMutableString alloc] initWithString:initial];
[text appendString:[questions objectAtIndex:indexPath.section]];
NSInteger _stringLength=[text length];
NSMutableAttributedString *attString=[[NSMutableAttributedString alloc] initWithString:text];
[attString addAttribute:NSFontAttributeName
value:[UIFont fontWithName:#"Helvetica" size:20.0]
range:NSMakeRange(0, _stringLength)];
[attString addAttribute:NSForegroundColorAttributeName value:[UIColor whiteColor] range:NSMakeRange(0, _stringLength)];
headerView.label.attributedText = attString;
view = headerView;
}
if(kind == UICollectionElementKindSectionFooter){
FooterView *footerview = (FooterView*)[collectView dequeueReusableSupplementaryViewOfKind:UICollectionElementKindSectionFooter withReuseIdentifier:#"FooterView" forIndexPath:indexPath];
footerview.addLine.tag = indexPath.section;
[footerview.addLine addTarget:self action:#selector(addLine:) forControlEvents: UIControlEventTouchUpInside];
view = footerview;
}
return view;
}
- (CGSize)collectionView:(UICollectionView *)collecView layout:(UICollectionViewLayout*)collectionViewLayout referenceSizeForFooterInSection:(NSInteger)section
{
if(section%2 !=0)
{
return CGSizeZero;
}
UICollectionViewFlowLayout *flowLayout = (UICollectionViewFlowLayout *)collectionView.collectionViewLayout;
return CGSizeMake(flowLayout.itemSize.width, 100);
}
- (CGSize)collectionView:(UICollectionView *)collecView layout:(UICollectionViewLayout*)collectionViewLayout referenceSizeForHeaderInSection:(NSInteger)section
{
UICollectionViewFlowLayout *flowLayout = (UICollectionViewFlowLayout *)collectionView.collectionViewLayout;
return CGSizeMake(flowLayout.itemSize.width, 100);
}

Answer 1

I found the solution :
After removing the following lines :
UICollectionViewFlowLayout *flowLayout = (UICollectionViewFlowLayout *)collectionView.collectionViewLayout;
UIInterfaceOrientation interfaceOrientation = [[UIApplication sharedApplication] statusBarOrientation];
if(UIInterfaceOrientationIsPortrait(interfaceOrientation)){
[flowLayout setItemSize:CGSizeMake(screenWidth-6, 50)];
}else if(UIInterfaceOrientationIsLandscape(interfaceOrientation)){
[flowLayout setItemSize:CGSizeMake(screenHeight-24, 50)];
}
in the method :
- (UICollectionViewCell*) collectionView:(UICollectionView *)collectView cellForItemAtIndexPath:(NSIndexPath *)indexPath
the problem seems to be gone. I think the setting up of the cells in my UiCollectionView was taking to much time, which caused my problem with the footers/headers and the empty array.
This was my code :
- (UICollectionViewCell*) collectionView:(UICollectionView *)collectView cellForItemAtIndexPath:(NSIndexPath *)indexPath {
UICollectionViewCell *view;
if(indexPath.section %2 == 0){
//create collection view cell
QuestionCell *cell = (QuestionCell *)[collectView dequeueReusableCellWithReuseIdentifier:#"QuestionCell" forIndexPath:indexPath];
[cell setTag:indexPath.section];
//configure cell :
[cell.textView setTag:indexPath.item];
[cell.suppress setTag:indexPath.section];
[cell.suppress addTarget:self action:#selector(deleteLine:) forControlEvents: UIControlEventTouchUpInside];
view = cell;
}else{
YesNo *cell = (YesNo*)[collectView dequeueReusableCellWithReuseIdentifier:#"YesNo" forIndexPath:indexPath];
UICollectionViewFlowLayout *flowLayout = (UICollectionViewFlowLayout *)collectionView.collectionViewLayout;
UIInterfaceOrientation interfaceOrientation = [[UIApplication sharedApplication] statusBarOrientation];
if(UIInterfaceOrientationIsPortrait(interfaceOrientation)){
[flowLayout setItemSize:CGSizeMake(screenWidth-6, 50)];
}else if(UIInterfaceOrientationIsLandscape(interfaceOrientation)){
[flowLayout setItemSize:CGSizeMake(screenHeight-24, 50)];
}
[cell setTag:indexPath.section];
view = cell;
}
return view;
}
And I changed it to this :
- (UICollectionViewCell*) collectionView:(UICollectionView *)collectView cellForItemAtIndexPath:(NSIndexPath *)indexPath {
UICollectionViewCell *view;
if(indexPath.section %2 == 0){
//create collection view cell
QuestionCell *cell = (QuestionCell *)[collectView dequeueReusableCellWithReuseIdentifier:#"QuestionCell" forIndexPath:indexPath];
[cell setTag:indexPath.section];
//configure cell :
[cell.textView setTag:indexPath.item];
[cell.suppress setTag:indexPath.section];
[cell.suppress addTarget:self action:#selector(deleteLine:) forControlEvents: UIControlEventTouchUpInside];
view = cell;
}else{
YesNo *cell = (YesNo*)[collectView dequeueReusableCellWithReuseIdentifier:#"YesNo" forIndexPath:indexPath];
[cell setTag:indexPath.section];
view = cell;
}
return view;
}