UICollectionView cells doesn't appear - swift

Question

I don't understand what's happening with my UICollectionView.
I'm apologise in advance because I think the answer is very simple
I just wan't to create a UICollectionView programmatically with 4 cells but 2 of them does not appear I don't know why
Here my code:
class NewsListViewController: UIViewController {
public var newsImagesCollectionView: UICollectionView!
override func viewWillLayoutSubviews() {
if self.newsImagesCollectionView == nil {
self.createNewsImagesCollectionView()
}
}
fileprivate func createNewsImagesCollectionView() {
let layout = UICollectionViewFlowLayout()
layout.scrollDirection = .horizontal
layout.minimumInteritemSpacing = 0
layout.minimumLineSpacing = 0
self.newsImagesCollectionView = UICollectionView(frame: .zero, collectionViewLayout: layout)
self.newsImagesCollectionView.dataSource = self
self.newsImagesCollectionView.delegate = self
self.newsImagesCollectionView.register(NewsImagesCollectionViewCell.self, forCellWithReuseIdentifier: NewsImagesCollectionViewCell.reuseIdentifier)
self.newsImagesCollectionView.backgroundColor = .yellow
self.newsImagesCollectionView.translatesAutoresizingMaskIntoConstraints = false
self.view.addSubview(self.newsImagesCollectionView)
self.newsImagesCollectionView.bottomAnchor.constraint(equalTo: self.view.bottomAnchor).isActive = true
self.newsImagesCollectionView.topAnchor.constraint(equalTo: self.view.topAnchor).isActive = true
self.newsImagesCollectionView.leftAnchor.constraint(equalTo: self.view.leftAnchor).isActive = true
self.newsImagesCollectionView.rightAnchor.constraint(equalTo: self.view.rightAnchor).isActive = true
}
}
extension NewsListViewController: UICollectionViewDelegate, UICollectionViewDataSource, UICollectionViewDelegateFlowLayout {
func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
return 4
}
func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
let cell = collectionView.dequeueReusableCell(withReuseIdentifier: NewsImagesCollectionViewCell.reuseIdentifier, for: indexPath) as! NewsImagesCollectionViewCell
switch indexPath.row {
case 0:
cell.imageView.backgroundColor = .purple
case 1:
cell.imageView.backgroundColor = .green
case 2:
cell.imageView.backgroundColor = .orange
case 3:
cell.imageView.backgroundColor = .red
default:
cell.imageView.backgroundColor = .blue
}
cell.imageView.contentMode = .scaleAspectFit
cell.imageView.image = #imageLiteral(resourceName: "euro")
return cell
}
func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, sizeForItemAt indexPath: IndexPath) -> CGSize {
print(self.view.frame.width)
return CGSize(width: self.view.frame.width / 4, height: self.view.frame.height)
}
func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, insetForSectionAt section: Int) -> UIEdgeInsets {
return UIEdgeInsets(top: 0, left: 0, bottom: 0, right: 0)
}
}
And I get this:
enter image description here
Thanks for your help

Answer 1

Does your collection view has the same size than your main view? because you calculating the size with the main view, is better if you use the collection view size.
return CGSize(width: collectionView.frame.width / 4, height: collectionView frame.height)