self sizing collectionView with flowLayout - ios

Question

When I use collectionView without
let flowLayout = collectionView.collectionViewLayout as! UICollectionViewFlowLayout
flowLayout.estimatedItemSize = CGSize (width: self.collectionView.frame.width, height: 100)
then all the cells are displayed but when I use flowLayout then cells are not displayed I've been sitting here for a week on this and can not understand why this is happening.
here my code
override func viewDidLoad() {
super.viewDidLoad()
collectionView.delegate = self
collectionView.dataSource = self
let flowLayout = collectionView.collectionViewLayout as! UICollectionViewFlowLayout
flowLayout.estimatedItemSize = CGSize(width: self.collectionView.frame.width, height: 100)
requestD(url: url)
}
// MARK: UICollectionViewDataSource
func numberOfSections(in collectionView: UICollectionView) -> Int {
return 1
}
func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
return modals.count
}
func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
if modals.count == 0 {
return UICollectionViewCell()
}
let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "cell", for: indexPath) as! CollectionViewCellAudio
cell.name?.text = modals[indexPath.row].name
let u = URL(string: "http://www.---.com" + (modals[indexPath.row].ImageViewURL))
cell.ImageView.sd_setImage(with: u, placeholderImage: UIImage(named: "white"),
options: [.continueInBackground,.scaleDownLargeImages]) { (image, error, cacheType, url) in
self.modals[indexPath.row].ImageView = cell.ImageView.image!
}
return cell
}
func requestD(url:String){
var urlRequest = URLRequest(url: URL(string: url)!)
urlRequest.timeoutInterval = 300
let task = URLSession.shared.dataTask(with: urlRequest) { (data,response,error) in
if error != nil{
print(error ?? 0)
return
}
do{
let json = try JSONSerialization.jsonObject(with: data!, options: .mutableContainers) as! [String : Any]
if let main = json["LIBRARY"] as? [String:[String : Any]]{
for (_, data) in main {
let info = ModalAudio()
info.id = data["ID"] as? String
info.name = data["NAME"] as? String
info.AboutBook = data["DETAIL_TEXT"] as? String
info.ImageViewURL = data["PICTURE"] as! String
self.modals.append(info)
}
}
} catch let error {
print(error)
}
DispatchQueue.main.sync {
self.isMoreDataLoading = false
self.iNumPage += 1
}
}
self.collectionView?.reloadData()
task.resume()
}

Answer 1

In the viewDidLoad the frame of your collection view is undefined yet, so put this code in your viewDidLayoutSubView method, after reviewing your project your issues is related to use of flowLayout.estimatedItemSize as you can read in the property declaration comment
#available(iOS 8.0, *)
open var estimatedItemSize: CGSize // defaults to CGSizeZero - setting a non-zero size enables cells that self-size via -preferredLayoutAttributesFittingAttributes:
So use this code, it works!
override func viewDidLayoutSubviews() {
super.viewDidLayoutSubviews()
let flowLayout = collectionView.collectionViewLayout as! UICollectionViewFlowLayout
//flowLayout.estimatedItemSize = CGSize(width: self.collectionView.frame.width, height: 100) don't show your cells
flowLayout.itemSize = CGSize(width: self.collectionView.frame.width, height: 100)//show your cells
flowLayout.invalidateLayout()
}
Hope this helps