Question

I’m trying to display a decoration view behind each row in a UIViewController.

Each “row” has 3 UICollectionViewCells. I’d like to display a background through a decoration view behind the row of three cells.

In viewDidLoad: I am registering the decoration view:

[self.collectionView.collectionViewLayout registerClass:[CollectionRowDecorationView class] forDecorationViewOfKind:@"RowDecorationView"];

I’ve also setup the following delegate method:

- (UICollectionViewLayoutAttributes *)layoutAttributesForDecorationViewOfKind:(NSString *)decorationViewKind atIndexPath:(NSIndexPath *)indexPath
{
    UICollectionViewLayoutAttributes *layoutAttributes = [UICollectionViewLayoutAttributes layoutAttributesForDecorationViewOfKind:decorationViewKind withIndexPath:indexPath];
    layoutAttributes.frame = CGRectMake(0.0, 0.0, self.collectionView.contentSize.width, self.collectionView.contentSize.height);
    layoutAttributes.zIndex = -1;
    return layoutAttributes;
}

Unfortunately the delegate method does not get called. I am not 100% clear from reading the documentation what I need to do in order for the decoration view to get initialized? It looks like I am missing another delegate method that needs to get called in order for everything to get setup properly.

Thanks!

Answer 1

You need to add the decorationview in - (NSArray *)layoutAttributesForElementsInRect:(CGRect)rect like this:

[attributesArray addObject:[self layoutAttributesForDecorationViewOfKind:@"BackgroundView" atIndexPath:[NSIndexPath indexPathForRow:0 inSection:0]]];