Programmatically declared UICollectionView does not change the size of cell in Swift 5

Question

I am declaring a UICollectionView and its corresponding cell programatically. After writing out the vanilla setup, I find that I cannot configure the size of the cell. Regardless of whether i place the logic, or what dimension, the cells (in red) appear to be some default square (and small) size. A screen capture is at the end of this post.

For reference, the code is below:

setupView(){}
    // collection view for screens
    let screenHeight : CGFloat = CGFloat(height/6)
    let screenWidth = screenHeight * ( width/height )
    let offset_top_screens : CGFloat = height - rowHeight - screenHeight

    let screenRow = UICollectionView(
          frame: CGRect(x: 0, y: offset_top_screens, width: width, height: screenHeight)
        , collectionViewLayout: UICollectionViewFlowLayout()
    )

    //screenRow.translatesAutoresizingMaskIntoConstraints = false

    screenRow.backgroundColor = Color.grayTertiary

    // set up collection view delegates
    screenRow.dataSource = self
    screenRow.alwaysBounceHorizontal = true

    screenRow.register(ScreenItem.self, forCellWithReuseIdentifier: ScreenItem.identifier) // register w/ storyboard

    self.view.addSubview(screenRow)
    self.screenRow = screenRow
    self.view.bringSubviewToFront(screenRow)
    self.screenHeight = screenHeight
    self.screenWidth  = screenWidth
    // end collection view screen

}


func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
    return dataSource.count
}

func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {

    let row = indexPath.row
    let user = self.dataSource[row]
    let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "ScreenItem", for: indexPath) as! ScreenItem

    /*
     cell.uuid        = user.uuid
     cell.delegate    = self
     cell.mediaSource = ... what is the pipe here?
     */
    return cell
}


func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, sizeForItemAt indexPath: IndexPath) -> CGSize {        

    return CGSize(width: 45, height:40)  // changing these values do not change anything
    // return CGSize(width: 90, height: collectionView.bounds.height)   <- this does nothing


}


func collectionView(_ collectionView: UICollectionView,
                    layout collectionViewLayout: UICollectionViewLayout,
                    insetForSectionAt section: Int) -> UIEdgeInsets {
    return UIEdgeInsets(top: 0, left: 0, bottom: 0, right: 0) //.zero
}

func collectionView(_ collectionView: UICollectionView,
                    layout collectionViewLayout: UICollectionViewLayout,
                    minimumInteritemSpacingForSectionAt section: Int) -> CGFloat {
    return 0
}

func collectionView(_ collectionView: UICollectionView,
                    layout collectionViewLayout: UICollectionViewLayout,
                    minimumLineSpacingForSectionAt section: Int) -> CGFloat {
    return 0
}



// somewhere in a different file


/*
 @Use: display user's screen
 */
class ScreenItem: UICollectionViewCell {

    static var identifier: String = "ScreenItem"

    weak var textLabel: UILabel!

    override init(frame: CGRect) {
        super.init(frame: frame)
        self.backgroundColor = Color.red
    }

    required init?(coder aDecoder: NSCoder) {
        super.init(coder: aDecoder)
    }

    override func prepareForReuse() {
        super.prepareForReuse()
        self.reset()
    }

    func reset() {
        // @TOOD: reset things here
    }
}

__ update __ parent class definition

class CallController:
  UIViewController
, UICollectionViewDataSource
, UICollectionViewDelegate

Answer 1

You don't seem to set a delegate. If you are using the UICollectionViewFlowLayout then your UIViewController should implement the UICollectionViewDelegateFlowLayout protocol.

UICollectionViewDelegateFlowLayout

Does your UIViewController instance already implement this protocol? Did you set the delegate property?