// reference: https://stackoverflow.com/a/42705208/1477298
You can do a lot of fun stuff to collection views. I like to subclass UICollectionViewFlowLayout. Here is an example that fades the top and the bottom of the collection view based on distance from center. I could modify it to fade only the very edges but you should figure it after you look through the code.
import UIKit
class FadingLayout: UICollectionViewFlowLayout,UICollectionViewDelegateFlowLayout {
//should be 0<fade<1
private let fadeFactor: CGFloat = 0.5
private let cellHeight : CGFloat = 60.0
required init?(coder aDecoder: NSCoder) {
super.init(coder: aDecoder)
}
init(scrollDirection:UICollectionViewScrollDirection) {
super.init()
self.scrollDirection = scrollDirection
}
override func prepare() {
setupLayout()
super.prepare()
}
func setupLayout() {
self.itemSize = CGSize(width: self.collectionView!.bounds.size.width,height:cellHeight)
self.minimumLineSpacing = 0
}
override func shouldInvalidateLayout(forBoundsChange newBounds: CGRect) -> Bool {
return true
}
func scrollDirectionOver() -> UICollectionViewScrollDirection {
return UICollectionViewScrollDirection.vertical
}
//this will fade both top and bottom but can be adjusted
override func layoutAttributesForElements(in rect: CGRect) -> [UICollectionViewLayoutAttributes]? {
let attributesSuper: [UICollectionViewLayoutAttributes] = super.layoutAttributesForElements(in: rect) as [UICollectionViewLayoutAttributes]!
if let attributes = NSArray(array: attributesSuper, copyItems: true) as? [UICollectionViewLayoutAttributes]{
var visibleRect = CGRect()
visibleRect.origin = collectionView!.contentOffset
visibleRect.size = collectionView!.bounds.size
for attrs in attributes {
if attrs.frame.intersects(rect) {
let distance = visibleRect.midY - attrs.center.y
let normalizedDistance = abs(distance) / (visibleRect.height * fadeFactor)
let fade = 1 - normalizedDistance
attrs.alpha = fade
}
}
return attributes
}else{
return nil
}
}
//appear and disappear at 0
override func initialLayoutAttributesForAppearingItem(at itemIndexPath: IndexPath) -> UICollectionViewLayoutAttributes? {
let attributes = super.layoutAttributesForItem(at: itemIndexPath)! as UICollectionViewLayoutAttributes
attributes.alpha = 0
return attributes
}
override func finalLayoutAttributesForDisappearingItem(at itemIndexPath: IndexPath) -> UICollectionViewLayoutAttributes? {
let attributes = super.layoutAttributesForItem(at: itemIndexPath)! as UICollectionViewLayoutAttributes
attributes.alpha = 0
return attributes
}
}
And in your setup in your controller with the collection view it would look like this.
let layout = FadingLayout(scrollDirection: .vertical)
collectionView.delegate = self
collectionView.dataSource = self
self.collectionView.setCollectionViewLayout(layout, animated: false)
I can tell you how to modify it if I knew the use case a bit better.
Like your work. Just don't understand how to create a single side fade (f.i. top) or reducing the size to just top 5%. Is there away you can help me ?