How to calculate iOS 11 size in different orientation? - ios

Question

I calculate itemSize dependent on safe area for UICollectionView with horizontal scroll and custom layout.
But for iPhone X safe area has different size for different orientation. My question is how should I calculate safe area size for landscape orientation in viewWillTransition function? Or how is it possible to do without this calculation?

Answer 1

EDIT
To get safe area size without creating any additional views, use this:
view.safeAreaLayoutGuide.layoutFrame.size
If you want to use viewWillTransition method you can use this:
override func viewWillTransition(to size: CGSize, with coordinator: UIViewControllerTransitionCoordinator) {
super.viewWillTransition(to: size, with: coordinator)
// Before rotation
print(view.safeAreaLayoutGuide.layoutFrame.size)
coordinator.animate(alongsideTransition: { (context) in
// During rotation
}) { (context) in
// After rotation
print(self.view.safeAreaLayoutGuide.layoutFrame.size)
}
}
In the completion block you will get your desired size, note however, that this code will be called after the rotation.
Original answer
Solution using additional UIView:
What I did was to create a UIView and pin it with constant 0 to Safe Area Guides, so that it always matches size of Safe Area:
I created an #IBOutlet of that UIView and in viewDidLayoutSubviews() check the size:
override func viewDidLayoutSubviews() {
super.viewDidLayoutSubviews()
print(containerView.frame.size)
}
After rotation I also get the updated size of that UIView.

Answer 2

Use UICollectionViewDelegateFlowLayout's collectionView(_:layout:sizeForItemAt:). Works like a charm.
Setting the size in the completion block of coordinator.animate(alongsideTransition:completion:) in viewWillTransition(to:with:) didn't work for me because the size animation occurs after the orientation animation ends, which looks weird.