Если вы хотите использовать UICollectionView, просто возьмите делегата, посмотрите, в каком направлении прокручивается пользователь, и при необходимости скройте / покажите заголовок. Вот пример, с которого можно начать:
class ViewController: UIViewController {
// Variable to save the last scroll offset.
private var lastContentOffset: CGFloat = 0
private lazy var header: UIView = {
let header = UIView()
header.translatesAutoresizingMaskIntoConstraints = false
header.backgroundColor = .red
header.widthAnchor.constraint(equalToConstant: self.view.frame.width).isActive = true
header.heightAnchor.constraint(equalToConstant: 80.0).isActive = true
return header
}()
private lazy var collectionView: UICollectionView = {
let collectionView = UICollectionView(frame: .zero, collectionViewLayout: UICollectionViewLayout())
collectionView.translatesAutoresizingMaskIntoConstraints = false
collectionView.delegate = self
collectionView.backgroundColor = .white
collectionView.contentSize = CGSize(width: UIScreen.main.bounds.width, height: 2000.0)
// Setting bounces to false - otherwise the header will disappear when we go past the top and are sprung back.
collectionView.bounces = false
return collectionView
}()
override func viewDidLoad() {
super.viewDidLoad()
self.view.addSubview(collectionView)
collectionView.leftAnchor.constraint(equalTo: self.view.leftAnchor).isActive = true
collectionView.rightAnchor.constraint(equalTo: self.view.rightAnchor).isActive = true
collectionView.topAnchor.constraint(equalTo: self.view.topAnchor).isActive = true
collectionView.bottomAnchor.constraint(equalTo: self.view.bottomAnchor).isActive = true
collectionView.contentSize = CGSize(width: UIScreen.main.bounds.width, height: 2000.0)
// Make sure you either add the header subview last, or call self.view.bringSubviewToFront(header)
self.view.addSubview(header)
// Constrain the header so it's just sitting on top of the view. To make it visible, we'll use a transform.
header.bottomAnchor.constraint(equalTo: self.view.topAnchor).isActive = true
header.centerXAnchor.constraint(equalTo: self.view.centerXAnchor).isActive = true
// Header starts visible.
header.layoutIfNeeded()
self.header.transform = CGAffineTransform(translationX: 0.0, y: header.frame.height)
}
func revealHeader() {
// Set the duration below to how quickly you want header to appear/disappear.
UIView.animate(withDuration: 0.3) {
self.header.transform = CGAffineTransform(translationX: 0.0, y: self.header.frame.height)
}
}
func hideHeader() {
UIView.animate(withDuration: 0.3) {
self.header.transform = .identity
}
}
}
extension ViewController: UICollectionViewDelegate {
func scrollViewDidScroll(_ scrollView: UIScrollView) {
if (lastContentOffset > scrollView.contentOffset.y) {
// Scrolled up: reveal header.
revealHeader()
}
else if (lastContentOffset < scrollView.contentOffset.y) {
// Scrolled down: reveal header.
hideHeader()
}
lastContentOffset = scrollView.contentOffset.y
}
}
РЕДАКТИРОВАТЬ: Заметил, что функциональность заголовка Reddit немного отличается. Если вы хотите, чтобы вещь динамически прокручивалась (то есть на сумму, на которую вы прокручивались, а не появлялась сразу), замените эту функцию делегата на:
func scrollViewDidScroll(_ scrollView: UIScrollView) {
if (lastContentOffset > scrollView.contentOffset.y) {
// Scrolled up: reveal header.
let difference = lastContentOffset - scrollView.contentOffset.y
if header.transform.ty < (header.frame.height - difference) {
// Header hasn't been fully revealed yet, bring it down by the amount we've scrolled up.
self.header.transform = CGAffineTransform(translationX: 0.0, y: header.transform.ty + difference)
} else {
self.header.transform = CGAffineTransform(translationX: 0.0, y: header.frame.height)
}
}
else if (lastContentOffset < scrollView.contentOffset.y) {
// Scrolled down: reveal header.
let difference = scrollView.contentOffset.y - lastContentOffset
if header.transform.ty > difference {
self.header.transform = CGAffineTransform(translationX: 0.0, y: header.transform.ty - difference)
} else {
self.header.transform = CGAffineTransform(translationX: 0.0, y: 0.0)
}
}
lastContentOffset = scrollView.contentOffset.y
}