change the height of a UICollectionReuseableView (collection section header) dynamically

Question

I am trying to set the height of the section headers for a UICollectionView dynamically, but using the code below, I am not seeing anything change. The view is drawn with the correct items in it but the height will not budge. Sorry if this is a repeat question, but I can't seem to find anything related specifically to the UICollectionView object. Thanks in advance.

- (UICollectionReusableView *)collectionView:(UICollectionView *)collectionView
           viewForSupplementaryElementOfKind:(NSString *)kind
                                 atIndexPath:(NSIndexPath *)indexPath
{
    PhotoVideoHeaderCell *headerView = [collectionView dequeueReusableSupplementaryViewOfKind:UICollectionElementKindSectionHeader
                                                                          withReuseIdentifier:@"videoHeaderView"
                                                                                 forIndexPath:indexPath];
    if (indexPath.section == 0) {
        // photos
        [headerView setSection:@"Photo"];
    } else {
        [headerView.VehicleDetailView removeFromSuperview];
        CGRect frame = headerView.frame;
        frame.size.height = 60;
        [headerView setFrame:frame];
        [headerView setNeedsDisplay];
        [headerView setBackgroundColor:[UIColor grayColor]];
        [headerView setSection:@"Video"];
    }

    return headerView;
}

Corena

Answer 1

Your delegate should implement the following function, assuming you're using a flow layout:

- (CGSize)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout*)collectionViewLayout referenceSizeForHeaderInSection:(NSInteger)section;

You can return a different size for each header. In horizontally scrolling collection views, only the width is used. In vertically scrolling ones, only the height is used. The unused value is ignored — your view will always be stretched to fill the full height/width of horizontal/vertical collection views, respectively.

There is a corresponding method for footers, too.

Medellin

this works, but how do i tell which section i am editing, i only want to do it for section at index 1 – Corena

Use the section parameter in the method. Store which section you're editing in an ivar and then compare them. If they're not the same, return the layout's headerReferenceSize. – Medellin

sorry for being a complete noob here but the headerReferenceSize is not part of the collectionViewLayout... do i need to create an instance of the header to read the frame? – Corena

Nope - cast the collectionViewLayout — return [(UICollectionViewFlowLayout *)self.collectionView.collectionViewLayout headerReferenceSize];. – Medellin

Hero again @AshFurrow - that is exactly what I was after, perfect :) Thank you! – Overcasting

Answer 2

Accepted answer in Swift 3 and 4:

func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, referenceSizeForHeaderInSection section: Int) -> CGSize {
    return CGSize(width: collectionView.frame.size.width, height: 250)
}

Toh

Answer 3

Well, instead of using the noisy delegate method, I prefer using this: (only works if you have a unique header size)

    let layout = self.collectionView.collectionViewLayout as! UICollectionViewFlowLayout // Assuming you use the default flow layout 
    layout.headerReferenceSize = CGSize(width: 42, height: 42) //Set the header size

Works also with the itemSize:

    layout.itemSize = CGSize(width: 42, height: 42) //Set a custom item size

This works great for setting an item size relative to your screen width for exemple.

Anstus

Answer 4

Try something like this:

- (UICollectionReusableView *)collectionView:(UICollectionView *)collectionView viewForSupplementaryElementOfKind:(NSString *)kind atIndexPath:(NSIndexPath *)indexPath {
    UICollectionReusableView *header = [siteMapCollection dequeueReusableSupplementaryViewOfKind: UICollectionElementKindSectionHeader withReuseIdentifier: @"headerID" forIndexPath: indexPath];
    NSString *headerText = @"This is my header";
    UIFont *labFont = [UIFont fontWithName: @"HelveticaNeue-CondensedBold" size: 20.0];
    CGSize textSize = [dummyText sizeWithFont: labFont];
    UILabel *headerLabel = [[UILabel alloc] initWithFrame: CGRectMake(0, header.frame.size.height - (textSize.height + 12), header.frame.size.width, textSize.height + 8)];
    [headerLabel setFont: labFont];

    [header addSubview: headerLabel];

    return header;
}

Bijou