UICollectionview how to avoide top bar by scrolling - ios

Question

When I start my App everything is fine.
As it should stay.
But as soon I start to scroll down a strange Bar at the Top appears.
Strange Bar by Scrolling down
I looked for some frame issue but I can't find one. I have no Idea what causes this behavior. I coded my UICollectionview programmatically.
Here is my Code:
import UIKit
// MARK: Erzeugung & Füllen des Daten STRUCT
struct Profile {
let name: String
let location: String
let imageName: String
let profession: String
}
var profiles: [Profile] = []
private func populateProfiles() {
profiles = [
Profile(name: "Thor", location: "Boston", imageName: "astronomy", profession: "astronomy"),
...
Profile(name: "Elon Musk", location: "San Francisco", imageName: "graduate", profession: "graduate")
]
}
class ViewController: UIViewController {
private let collectionView: UICollectionView = {
let viewLayout = UICollectionViewFlowLayout()
let collectionView = UICollectionView(frame: .zero, collectionViewLayout: viewLayout)
// collectionView.backgroundColor = .white
return collectionView
}()
// MARK: Hintergrundbild erzeugen
let imageView : UIImageView = {
let iv = UIImageView()
iv.image = UIImage(named:"Backround-wood")
iv.contentMode = .scaleAspectFill
return iv
}()
private enum LayoutConstant {
static let spacing: CGFloat = 50.0 //Größe der Zwischenräume
static let itemHeight: CGFloat = 500.0 //Zellhöhe
}
override func viewDidLoad() {
super.viewDidLoad()
setupViews()
setupLayouts()
populateProfiles() // finales Befüllen des STRUCT
collectionView.reloadData()
self.collectionView.backgroundView = imageView //Hintergrundbild einfügen
}
// MARK: Rotation - Resize-Cells & Transition
override func viewWillTransition(to size: CGSize, with coordinator: UIViewControllerTransitionCoordinator) {
super.viewWillTransition(to: size, with: coordinator)
coordinator.animate(
alongsideTransition: { _ in self.collectionView.collectionViewLayout.invalidateLayout() },
completion: { _ in }
)
}
private func setupViews() {
view.backgroundColor = .white
view.addSubview(collectionView)
collectionView.dataSource = self
collectionView.delegate = self
collectionView.register(ProfileCell.self, forCellWithReuseIdentifier: ProfileCell.identifier)
collectionView.contentInsetAdjustmentBehavior = .never // Cells starten weiter oben
}
// MARK: Constraints collectionView
private func setupLayouts() {
collectionView.translatesAutoresizingMaskIntoConstraints = false
NSLayoutConstraint.activate([
collectionView.topAnchor.constraint(equalTo: view.topAnchor), //view.safeAreaLayoutGuide.topAnchor),
collectionView.bottomAnchor.constraint(equalTo: view.bottomAnchor), //view.safeAreaLayoutGuide.bottomAnchor),
collectionView.leftAnchor.constraint(equalTo: view.leftAnchor),
collectionView.rightAnchor.constraint(equalTo: view.rightAnchor)
])
}
init() {
super.init(nibName: nil, bundle: nil)
}
required init?(coder: NSCoder) {
fatalError("init(coder:) has not been implemented")
}
}
extension ViewController: UICollectionViewDataSource {
func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
return profiles.count
}
func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
let cell = collectionView.dequeueReusableCell(withReuseIdentifier: ProfileCell.identifier, for: indexPath) as! ProfileCell
let profile = profiles[indexPath.row]
cell.setup(with: profile)
cell.contentView.backgroundColor = .red
return cell
}
}
extension ViewController: UICollectionViewDelegateFlowLayout {
func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, sizeForItemAt indexPath: IndexPath) -> CGSize {
let width = itemWidth(for: view.frame.width, spacing: LayoutConstant.spacing)
return CGSize(width: width, height: LayoutConstant.itemHeight)
}
func itemWidth(for width: CGFloat, spacing: CGFloat) -> CGFloat {
let itemsInRow: CGFloat = 2
let totalSpacing: CGFloat = 2 * spacing + (itemsInRow - 1) * spacing
let finalWidth = (width - totalSpacing) / itemsInRow
return floor(finalWidth)
}
func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, insetForSectionAt section: Int) -> UIEdgeInsets {
return UIEdgeInsets(top: LayoutConstant.spacing, left: LayoutConstant.spacing, bottom: LayoutConstant.spacing, right: LayoutConstant.spacing)
}
func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, minimumLineSpacingForSectionAt section: Int) -> CGFloat {
return LayoutConstant.spacing
}
func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, minimumInteritemSpacingForSectionAt section: Int) -> CGFloat {
return LayoutConstant.spacing
}
}
Can somebody please help?

Answer 1

This is probably a navigation bar that is initially invisible in iOS 15, but becomes visible when content is being scrolled underneath.
You can hide the navigation bar by adding this in viewDidLoad or viewDidAppear :
navigationController?.setNavigationBarHidden(true, animated: false)