UICollectionViewCell only shown when debug step by step - ios

Question

I can't get my custom UICollectionViewCell to be shown when run without put a breakpoint in func collectionView(collectionView: UICollectionView, cellForItemAtIndexPath indexPath: NSIndexPath) -> UICollectionViewCell and debug step by step through it. After that my custom cells will be shown fine. Something wrong from xcode builder or my code?
p/s: I register my custom UICollectionViewCell by className like this: clvDishes.registerClass(PosItemsCollectionViewCell.classForCoder(), forCellWithReuseIdentifier: "DishesCollectionViewCell") and create cell's layout all in code(not using xib file)
Here is my code
class PosCollectionViewSource<T>: NSObject, UICollectionViewDataSource, UICollectionViewDelegateFlowLayout {
var items:[T] = []
var identifier:String!
override init() {
}
func numberOfSectionsInCollectionView(collectionView: UICollectionView) -> Int {
return 1
}
func collectionView(collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
return items.count
}
func collectionView(collectionView: UICollectionView, cellForItemAtIndexPath indexPath: NSIndexPath) -> UICollectionViewCell {
let cell = collectionView.dequeueReusableCellWithReuseIdentifier(identifier + "CollectionViewCell", forIndexPath: indexPath)
switch(String(T)){
case "PosItemsInfo":
let itemsCell = cell as! PosItemsCollectionViewCell
let posItems = items as Any as! [PosItemsInfo]
itemsCell.updateCell(posItems[indexPath.item])
return itemsCell
default : break
}
return cell
}
}
class PosItemsCollectionViewCell: UICollectionViewCell{
private var _lblItemName:UILabel!
private var _lblItemPrice:UILabel!
private var _vOverlayInfo:UIView!
private var _imvPictureContainer:UIImageView!
private var _vSeparate:UIView!
private var _imvWarning:UIImageView!
private var _imvSeason:UIImageView!
private var _lblRemaining:UILabel!
override init(frame: CGRect) {
super.init(frame: frame)
let uiFont = UIFont(name: "HelveticaNeue-Thin", size: 17) as UIFont?
_lblItemName = UILabel()
_lblItemName.textColor = UIColor.whiteColor()
_lblItemName.font = uiFont
_lblItemPrice = UILabel()
_lblItemPrice.textColor = UIColor.whiteColor()
_lblItemPrice.font = uiFont
_vSeparate = UIView()
_vSeparate.backgroundColor = UIColor(hexString: "FFFFFF", a: 0.5)
_vOverlayInfo = UIView()
_vOverlayInfo.backgroundColor = UIColor(hexString: "#000000", a:0.21)
_imvPictureContainer = UIImageView()
_imvPictureContainer.image = UIImage(named: "pos_DefaultDishIcon")
_vOverlayInfo.addSubview(_lblItemName)
_vOverlayInfo.addSubview(_lblItemPrice)
_vOverlayInfo.addSubview(_vSeparate)
_lblRemaining = UILabel()
_lblRemaining.textColor = UIColor(hexString: "E86E2B")
_lblRemaining.SetBorder("E86E2B", radius: 0)
_lblRemaining.backgroundColor = UIColor.whiteColor()
_lblRemaining.font = UIFont(name: "HelveticaNeue-Medium", size: 20)
_lblRemaining.textAlignment = NSTextAlignment.Center
_imvSeason = UIImageView()
_imvSeason.image = UIImage(named: "pos_SeasonIcon")
_imvWarning = UIImageView()
contentView.addSubview(_imvPictureContainer)
contentView.addSubview(_vOverlayInfo)
contentView.backgroundColor = UIColor.whiteColor()
}
func updateCell(item:PosItemsInfo){
_lblItemName.text = item.itemName
_lblItemPrice.text = item.itemPrice?.toString("%.2f")
_lblRemaining.text = item.itemQtyRemaining?.toString()
if item.itemQtyStatus == PosItemQtyStatus.SoldOut{
contentView.addSubview(_imvWarning)
_imvWarning.image = UIImage(named: "pos_SoldOut")
}
else if item.itemQtyStatus == PosItemQtyStatus.LowInStock{
contentView.addSubview(_imvWarning)
contentView.addSubview(_lblRemaining)
_imvWarning.image = UIImage(named: "pos_LowStock")
_lblRemaining.text = item.itemQtyRemaining?.toString()
}
if item.itemIsSeason == true {
contentView.addSubview(_imvSeason)
}
}
override func layoutSubviews() {
_vOverlayInfo.frame = CGRect(x: 0, y: contentView.frame.height - 60, width: 205, height: 60)
_imvPictureContainer.frame = CGRect(x: 0, y: 0, width: 205, height: 160)
_lblItemName.frame = CGRect(x: 10, y: 0, width: contentView.frame.width - 20, height: _vOverlayInfo.frame.height/2 )
_lblItemPrice.frame = CGRect(x: 10, y: _lblItemName.frame.height, width: contentView.frame.width - 20, height: _vOverlayInfo.frame.height/2 )
_vSeparate.frame = CGRect(x: 8, y: _lblItemName.frame.height, width: contentView.frame.width - 16, height: 1 )
_lblRemaining.frame = CGRect(x: (contentView.frame.width - 50)/2, y: 40, width: 50, height: 50)
_imvWarning.frame = CGRect(x: 125, y: 0, width: 81, height: 74)
}
override func didMoveToSuperview() {
self.setNeedsLayout()
self.layoutIfNeeded()
}
required init?(coder aDecoder: NSCoder) {
super.init(coder:aDecoder)
}
class PosDishesVCtrl: PosBaseController {
#IBOutlet weak var clvDishes: UICollectionView!
private var _clvDataSource:PosCollectionViewSource<PosItemsInfo>!
private var _items:[PosItemsInfo]!
required init?(coder aDecoder: NSCoder) {
super.init(coder: aDecoder)
}
override init(nibName nibNameOrNil: String?, bundle nibBundleOrNil: NSBundle?) {
super.init(nibName: String(self.dynamicType), bundle: nil)
}
override func viewDidLoad() {
super.viewDidLoad()
modifiedOrUpdateUI()
renderDishes()
}
override func didReceiveMemoryWarning() {
super.didReceiveMemoryWarning()
}
func modifiedOrUpdateUI(){
clvDishes.setCollectionViewLayout(LayoutGridType, animated: false)
clvDishes.registerClass(PosItemsCollectionViewCell.classForCoder(), forCellWithReuseIdentifier: "DishesCollectionViewCell")
clvDishes.backgroundColor = UIColor(hexString: "979797", a: 1)
clvDishes.showsHorizontalScrollIndicator = false
clvDishes.showsVerticalScrollIndicator = false
clvDishes.pagingEnabled = false
clvDishes.autoresizingMask = UIViewAutoresizing.FlexibleWidth
clvDishes.contentSize = CGSize(width: clvDishes.frame.width, height: clvDishes.frame.height)
clvDishes.scrollsToTop = false
}
func renderDishes(){
if(_clvDataSource == nil){
_clvDataSource = PosCollectionViewSource<PosItemsInfo>()
_clvDataSource.identifier = "Dishes"
_items = [PosItemsInfo]()
}
for var i = 0; i < 12; i++ {
let item = PosItemsInfo()
item.itemName = "Dish " + String(i)
item.itemPrice = Double(i)
item.itemQtyRemaining = 4
if(i%2 == 0){
item.itemIsSeason = true
item.itemQtyStatus = PosItemQtyStatus.LowInStock
}
else {
item.itemQtyStatus = PosItemQtyStatus.SoldOut
}
_items.append(item)
}
clvDishes.setCollectionViewLayout(LayoutGridType, animated: false)
_clvDataSource.items = _items
clvDishes.dataSource = _clvDataSource
clvDishes.delegate = PosCollectionViewDelegate(ctr: self)
clvDishes.reloadData()
clvDishes.collectionViewLayout.invalidateLayout()
}
}
Any idea would be appreciate!

Answer 1

It looks like your DataSource method:
func collectionView(collectionView: UICollectionView, numberOfItemsInSection section: Int)
-> Int
{
return items.count
}
is always returning zero. Your row indices correspond to the number of items (cells) you'll return here.
EDIT:
Looking at the code you've provided, it isn't apparent that you ever add any items to the PosCollectionViewSource.items array, so I expect items.count to return zero. If it does not, then you must be adding items to the array somewhere else (in source code you haven't posted).
Looking at your code, I notice that the way you're setting up your custom cell class and using it is a bit complicated (possibly wrong) and could be better.
Assuming that you are adding elements to the items array somewhere, let's try a different approach:
Here's a pattern I use for cell types with reuseIdentifiers (UITableViewCell, UICollectionViewCell, etc.):
class CustomCell: UICollectionViewCell {
// This will do the right thing for CustomCell and its subclasses
class var reuseIdentifier: String { return "\(self)" }
}
Now, when you register the custom class, do it like this:
collectionView.registerClass(CustomCell.self, CustomCell.reuseIdentifier)
and fetch one like this:
func collectionView(collectionView: UICollectionView, cellForItemAtIndexPath indexPath: NSIndexPath) -> UICollectionViewCell {
let cell = collectionView.dequeueReusableCellWithReuseIdentifier(CustomCell.reuseIdentifier, forIndexPath: indexPath)
as! CustomCell
// setup the cell as necessary:
cell.contentView.backgroundColor = UIColor.yellowColor()
return cell
}

Answer 2

I had a very similar problem on iOS 14 (simulator & actual devices). Cells would only be displayed if I stopped running the app with a debug breakpoint before returning each cell.
A solution that worked for me was to call cell.setNeedsLayout() before returning the cells:
func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
let cell = collectionView.dequeueCellOfType(MyCell.self, for: indexPath)
// Make the call below:
cell.setNeedsLayout()
return cell
}