Select collection view cell on load - Custom UICollectionView class - ios

Question

I have a custom collection view (tabBarCollectionView), which should load with the first cell being selected, as per the code below. However, this is not working. I know this as the cell should be a different colour when selected, but isn't.
override init(frame: CGRect) {
super.init(frame: frame)
tabBarCollectionView.register(TabBarCell.self, forCellWithReuseIdentifier: cellIdentifier)
addSubview(tabBarCollectionView)
tabBarCollectionView.translatesAutoresizingMaskIntoConstraints = false
addConstraintsWithFormat("H:|[v0]|", views: tabBarCollectionView)
addConstraintsWithFormat("V:|[v0]|", views: tabBarCollectionView)
tabBarCollectionView.selectItem(at: IndexPath(item: 0, section: 0), animated: false, scrollPosition: [])
}
Full code of custom UIView class is inserted below:
import Foundation
import UIKit
class TabBar: UIView, UICollectionViewDataSource, UICollectionViewDelegate, UICollectionViewDelegateFlowLayout {
let cellIdentifier = "Cell"
let imageNames = ["homeIcon", "exploreIcon", "addIcon", "inboxIcon", "profileIcon"]
lazy var tabBarCollectionView: UICollectionView = {
// All collection view implementations in here
let layout = UICollectionViewFlowLayout()
let collectionView = UICollectionView(frame: .zero, collectionViewLayout: layout)
collectionView.dataSource = self
collectionView.delegate = self
collectionView.backgroundColor = UIColor.clear
return collectionView
}()
override init(frame: CGRect) {
super.init(frame: frame)
tabBarCollectionView.register(TabBarCell.self, forCellWithReuseIdentifier: cellIdentifier)
addSubview(tabBarCollectionView)
tabBarCollectionView.translatesAutoresizingMaskIntoConstraints = false
addConstraintsWithFormat("H:|[v0]|", views: tabBarCollectionView)
addConstraintsWithFormat("V:|[v0]|", views: tabBarCollectionView)
self.tabBarCollectionView.allowsSelection = true
self.tabBarCollectionView.selectItem(at: IndexPath(item: 0, section: 0), animated: false, scrollPosition: [])
}
override func layoutSubviews() {
super.layoutSubviews()
tabBarCollectionView.allowsSelection = true
tabBarCollectionView.selectItem(at: IndexPath(item: 0, section: 0), animated: false, scrollPosition: [])
}
func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
return 5
}
func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
let cell = collectionView.dequeueReusableCell(withReuseIdentifier: cellIdentifier, for: indexPath) as! TabBarCell
cell.backgroundColor = UIColor.clear
cell.tabBarImageView.image = UIImage(named: imageNames[indexPath.item])?.withRenderingMode(.alwaysTemplate)
cell.tabBarImageView.tintColor = UIColor.pinpointGrey
return cell
}
func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, sizeForItemAt indexPath: IndexPath) -> CGSize {
return CGSize(width: frame.width / 5, height: frame.height)
}
func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, minimumInteritemSpacingForSectionAt section: Int) -> CGFloat {
return 0
}
required init?(coder aDecoder: NSCoder) {
fatalError("init(coder:) has not been implemented")
}
}
class TabBarCell: UICollectionViewCell {
let tabBarImageView: UIImageView = {
let imageView = UIImageView()
imageView.image = UIImage(named: "homeIcon")?.withRenderingMode(.alwaysTemplate)
imageView.tintColor = UIColor.pinpointGrey
return imageView
}()
override init(frame: CGRect) {
super.init(frame: frame)
setupViews()
}
func setupViews() {
backgroundColor = UIColor.clear
addSubview(tabBarImageView)
addConstraintsWithFormat("H:[v0(42)]", views: tabBarImageView)
addConstraintsWithFormat("V:[v0(42)]", views: tabBarImageView)
addConstraint(NSLayoutConstraint(item: tabBarImageView, attribute: .centerX, relatedBy: .equal, toItem: self, attribute: .centerX, multiplier: 1, constant: 0))
addConstraint(NSLayoutConstraint(item: tabBarImageView, attribute: .centerY, relatedBy: .equal, toItem: self, attribute: .centerY, multiplier: 1, constant: 0))
}
override var isHighlighted: Bool {
didSet {
if tabBarImageView.isHighlighted == true {
self.tabBarImageView.tintColor = UIColor.pinpointBlue
} else {
self.tabBarImageView.tintColor = UIColor.pinpointGrey
}
}
}
override var isSelected: Bool {
didSet {
tabBarImageView.tintColor = isSelected ? UIColor.pinpointBlue : UIColor.pinpointGrey
}
}
required init?(coder aDecoder: NSCoder) {
fatalError("init(coder:) has not been implemented")
}
}

Answer 1

Where is your datasource set? Do you load it separately and then do a reloadData()?
If yes, then you should select the cell then and not during your viewDidLoad method as during load the collection view might not have been populated yet.
You could also add to a viewWillAppear/viewDidAppear method as this gets called after the collection view has been populated