UICollectionView Not Responding to Touch - ios

Question

I am trying to programmatically draw my CollectionView from within a custom class that subclasses UIView. The app loads up with no errors and the CollectionView is being drawn correctly as I can see the cell items, but the CollectionView does not respond to touch. When I try to scroll nothing happens.
I inspected the ViewController using the Debug View Hierarchy button in Xcode to see if there was possibly a view on top. There was not and I could see the cells clearly drawn separately.
Class:
class DrawUI_mainCollectionView : UIView, UICollectionViewDelegate, UICollectionViewDataSource {
override init(frame: CGRect) {
super.init(frame: frame)
setup()
}
var collectionView : UICollectionView?
private func setup() {
let layout: UICollectionViewFlowLayout = UICollectionViewFlowLayout()
layout.scrollDirection = .vertical
layout.itemSize = CGSize(width: CGFloat(kScreenWidth),height: 137)
let offset = 120.0
let collectionViewFrame = CGRect(x: 0, y: offset, width: Double(kScreenWidth), height: Double(kScreenHeight))
self.collectionView = UICollectionView(frame: collectionViewFrame, collectionViewLayout: layout)
self.collectionView!.alwaysBounceVertical = true
self.collectionView!.delegate = self
self.collectionView!.dataSource = self
self.collectionView!.register(UINib(nibName: "MealCategoryCell", bundle:Bundle.main), forCellWithReuseIdentifier: "cell")
self.addSubview(self.collectionView!)
}
func numberOfSections(in collectionView: UICollectionView) -> Int {
return 1
}
func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
return 20
}
func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "cell", for: indexPath) as! MealCategoryCell
cell.label.text = "test"
cell.textDescription.text = "textDescription"
return cell
}
func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, sizeForItemAt indexPath: IndexPath) -> CGSize {
return CGSize(width: kScreenWidth, height: 137)
}
func collectionView(_ collectionView: UICollectionView, didSelectItemAt indexPath: IndexPath) {
print("cell \(indexPath.row)")
}
required init?(coder aDecoder: NSCoder) {
fatalError("no storyboard...")
}
}
How I am implementing it on my ViewController
let collectionView = DrawUI_mainCollectionView()
self.view.addSubview(collectionView)
What am I doing wrong? Thanks in advance.

Answer 1

I think your main issue is not using auto layout, if you will add auto layout for the items:
view that contains the collectionView in viewController
collectionView in the view
It should work, the implementation:
In ViewController:
let collectionView = DrawUI_mainCollectionView()
collectionView.translatesAutoresizingMaskIntoConstraints = false
self.view.addSubview(collectionView)
NSLayoutConstraint(item: collectionView , attribute: .leading, relatedBy: .equal, toItem: self.view, attribute: .leadingMargin, multiplier: 1.0, constant: 0.0).isActive = true
NSLayoutConstraint(item: collectionView , attribute: .trailing, relatedBy: .equal, toItem: self.view, attribute: .trailingMargin, multiplier: 1.0, constant: 0.0).isActive = true
NSLayoutConstraint(item: collectionView , attribute: .top, relatedBy: .equal, toItem: self.view, attribute: .topMargin, multiplier: 1.0, constant: 0.0).isActive = true
NSLayoutConstraint(item: collectionView , attribute: .bottom, relatedBy: .equal, toItem: self.view, attribute: .bottomMargin, multiplier: 1.0, constant: 0.0).isActive = true
Inside the view:
private func setup() {
let layout: UICollectionViewFlowLayout = UICollectionViewFlowLayout()
layout.scrollDirection = .vertical
layout.itemSize = CGSize(width: CGFloat(kScreenWidth),height: 137)
let offset = 120.0
let collectionViewFrame = CGRect(x: 0, y: offset, width: Double(kScreenWidth), height: Double(kScreenHeight))
self.collectionView = UICollectionView(frame: collectionViewFrame, collectionViewLayout: layout)
self.collectionView!.alwaysBounceVertical = true
self.collectionView!.delegate = self
self.collectionView!.dataSource = self
self.collectionView!.register(UINib(nibName: "MealCategoryCell", bundle:Bundle.main), forCellWithReuseIdentifier: "cell")
self.collectionView!.translatesAutoresizingMaskIntoConstraints = false
self.addSubview(self.collectionView!)
NSLayoutConstraint(item: collectionView , attribute: .leading, relatedBy: .equal, toItem: self, attribute: .leadingMargin, multiplier: 1.0, constant: 0.0).isActive = true
NSLayoutConstraint(item: collectionView , attribute: .trailing, relatedBy: .equal, toItem: self, attribute: .trailingMargin, multiplier: 1.0, constant: 0.0).isActive = true
NSLayoutConstraint(item: collectionView , attribute: .top, relatedBy: .equal, toItem: self, attribute: .topMargin, multiplier: 1.0, constant: 0.0).isActive = true
NSLayoutConstraint(item: collectionView , attribute: .bottom, relatedBy: .equal, toItem: self, attribute: .bottomMargin, multiplier: 1.0, constant: 0.0).isActive = true
}