In iOS 12, when does the UICollectionView layout cells, use autolayout in nib

Question

Same code like this

collectionLayout.estimatedItemSize = CGSize(width: 50, height: 25)
collectionLayout.itemSize = UICollectionViewFlowLayoutAutomaticSize
co         


        

Answer 1

Solution 2 of Cœur's prevents the layout from flashing or updating in front of the user. But it can create problems when you rotate the device. I'm using a variable "shouldInvalidateLayout" in viewWillLayoutSubviews and setting it to false in viewDidAppear.

private var shouldInvalidateLayout = true

override func viewDidAppear(_ animated: Bool) {
    super.viewDidAppear(animated)

    shouldInvalidateLayout = false
}

override func viewWillLayoutSubviews() {
    super.viewWillLayoutSubviews()
    if shouldInvalidateLayout {
        collectionView.collectionViewLayout.invalidateLayout()
    }
}