MyUICollectionViewCell is not visible - ios

Question

import UIKit
private let reuseIdentifier = "NewCell"
class SeondViewController: UIViewController, UICollectionViewDelegateFlowLayout {
#IBOutlet var myNavBar: UINavigationBar!
var frutta: [String]!
override func viewDidLoad() {
super.viewDidLoad()
let margins = self.view.layoutMarginsGuide
let layout = UICollectionViewFlowLayout()
layout.sectionInset = UIEdgeInsets(top: 30, left: 10, bottom: 10, right: 10)
layout.scrollDirection = .vertical
let newCollectionView: UICollectionView = UICollectionView(frame: self.view.frame, collectionViewLayout: layout)
newCollectionView.dataSource = self
newCollectionView.delegate = self
newCollectionView.register(SecondTabCollectionViewCell.self, forCellWithReuseIdentifier: reuseIdentifier)
newCollectionView.reloadData()
newCollectionView.backgroundColor = UIColor.clear
newCollectionView.isHidden = false
newCollectionView.translatesAutoresizingMaskIntoConstraints = false
self.view.addSubview(newCollectionView)
frutta = ["Mele", "Olive", "Pere", "Noci", "Banane", "Kiwi", "Ananas"]
myNavBar.leadingAnchor.constraint(equalTo: margins.leadingAnchor).isActive = true
myNavBar.topAnchor.constraint(equalTo: margins.topAnchor).isActive = true
myNavBar.trailingAnchor.constraint(equalTo: margins.trailingAnchor).isActive = true
newCollectionView.leadingAnchor.constraint(equalTo: margins.leadingAnchor).isActive = true
newCollectionView.topAnchor.constraint(equalTo: myNavBar.bottomAnchor).isActive = true
newCollectionView.trailingAnchor.constraint(equalTo: margins.trailingAnchor).isActive = true
◦ newCollectionView.bottomAnchor.constraint(equalTo: margins.bottomAnchor).isActive = true
}
func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, sizeForItemAt indexPath: IndexPath) -> CGSize {
return CGSize(width: collectionView.bounds.size.width / 2, height: collectionView.bounds.size.height / 3)
}
}
extension SecondViewController: UICollectionViewDataSource {
func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
return frutta.count
}
func numberOfSections(in collectionView: UICollectionView) -> Int {
return 1
}
func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
let myCell = collectionView.dequeueReusableCell(withReuseIdentifier: reuseIdentifier, for: indexPath) as! SecondTabCollectionViewCell
myCell.backgroundColor = UIColor.clear
myCell.secondCellLabel = UILabel()
myCell.secondCellLabel.frame.size = CGSize(width: myCell.bounds.width / 2, height: myCell.secondCellLabel.bounds.height / 2)
myCell.secondCellLabel.adjustsFontSizeToFitWidth = true
myCell.secondCellLabel.backgroundColor = UIColor.clear
myCell.secondCellLabel.textColor = UIColor.black
myCell.secondCellLabel.text = frutta[indexPath.item]
myCell.translatesAutoresizingMaskIntoConstraints = false
myCell.contentView.addSubview(myCell.secondCellLabel)
return myCell
}
}
extension SecondViewController: UICollectionViewDelegate {
func collectionView(_ collectionView: UICollectionView, didSelectItemAt indexPath: IndexPath) {
print("Hai premuto \(indexPath.row).")
}
}
import UIKit
class SecondTabCollectionViewCell: UICollectionViewCell {
var secondCellLabel: UILabel!
override init(frame: CGRect) {
super.init(frame: frame)
}
required init?(coder aDecoder: NSCoder) {
fatalError("init(coder:) non e stato implementato.")
}
}

Answer 1

myCell.secondCellLabel.frame.size = CGSize(width: myCell.bounds.width / 2, height: myCell.secondCellLabel.bounds.height / 2)
The above line is wrong in cellForItemAt, you put the height of label is myCell.secondCellLabel.bounds.height instead of myCell.bounds.height.
correct one is
myCell.secondCellLabel.frame.size = CGSize(width: myCell.bounds.width / 2, height: myCell.bounds.height / 2)

Answer 2

It is a little strange to be laying out a cell's internal views in cellForRowAtIndexPath, this should be done in the cell class itself. The basic problem is that you your UILabel is appearing in the top left corner of the cell and has a height of zero, so you cannot see it. I moved the code you had in cellForRowAtIndexPath into the cell itself.
func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
let myCell = collectionView.dequeueReusableCell(withReuseIdentifier: reuseIdentifier, for: indexPath) as! SecondTabCollectionViewCell
myCell.backgroundColor = UIColor.clear
myCell.secondCellLabel.text = frutta[indexPath.item]
return myCell
}
import UIKit
class SecondTabCollectionViewCell: UICollectionViewCell {
var secondCellLabel: UILabel = {
let label = UILabel()
label.translatesAutoresizingMaskIntoConstraints = false
label.backgroundColor = .clear
label.textColor = .black
label.adjustsFontSizeToFitWidth = true
label.textAlignment = .center
return label
}()
override init(frame: CGRect) {
super.init(frame: frame)
configureViews()
}
required init?(coder aDecoder: NSCoder) {
super.init(coder: aDecoder)
}
private func configureViews() {
addSubview(secondCellLabel)
}
override func layoutSubviews() {
super.layoutSubviews()
configureLayout()
}
private func configureLayout() {
let width = bounds.width / 2
let height = frame.height / 2
let size = CGSize(width: width, height: height)
let origin = CGPoint(x: width/2, y: height/2)
secondCellLabel.frame = CGRect(origin: origin, size: size)
}
}