I collapse & expand sections by toggling numberOfItemsInSection:
. When collapsing, items disappear through alpha fade-out. I would like to change this effect to scaling them down.
I think I can implement this with custom UICollectionViewFlowLayout
and overloaded layoutAttributesForItemAtIndexPath:
. But when section collapses, numberOfItemsInSection:
returns 0 - so I can't set destination scale for that items.
What is correct approach?
Have found approach: we need to subclass UICollectionViewFlowLayout
and override finalLayoutAttributesForDisappearingItemAtIndexPath:
For example:
- (UICollectionViewLayoutAttributes *)finalLayoutAttributesForDisappearingItemAtIndexPath:(NSIndexPath *)itemIndexPath
{
UICollectionViewLayoutAttributes *attributes = [super finalLayoutAttributesForDisappearingItemAtIndexPath:itemIndexPath];
attributes.frame = CGRectInset(attributes.frame, 20, 20);
return attributes;
}