How to fix the wrong frame after device rotation? - swift

Question

I use custom alert view in my application. When called, its frame completely fills the screen. However, after the device rotates, it does not look right.
Then I try to change my alert frame and assign it a new screen size in viewWillTransition
override func viewWillTransition(to size: CGSize, with coordinator: UIViewControllerTransitionCoordinator) {
coordinator.animate(alongsideTransition: nil) { _ in UIView.setAnimationsEnabled(true) }
UIView.setAnimationsEnabled(false)
super.viewWillTransition(to: size, with: coordinator)
if let _ = alert {
alert?.rotateAlert(to: size)
Logger.Log("after size = \(alert?.backgroundView.frame.size)")
Logger.Log("after frame = \(alert?.frame)")
Logger.Log("after bounds = \(alert?.bounds)")
}
I tried to do the same in viewDidLayoutSubviews
override func viewDidLayoutSubviews() {
super.viewDidLayoutSubviews()
if let _ = alert {
Logger.Log("viewDidLayoutSubviews before rotation")
alert?.rotateAlert(to: self.view.frame.size)
Logger.Log("after size = \(alert?.backgroundView.frame.size)")
Logger.Log("after frame = \(alert?.frame)")
Logger.Log("after bounds = \(alert?.bounds)")
}
}
func rotateAlert(to size: CGSize) {
self.frame.size = size
backgroundView.frame = frame
}
Thus the frame of my alert changes. But its size is still smaller than the screen in height, thus forming an empty area.
Why is this happening? And how do I fix this? (I use Swift4)

Answer 1

To place your alert in the center of the screen, assuming that it is an instance of UIView, do this:
alert.centerXAnchor.constraint(equalTo: view.centerXAnchor).isActive = true
alert.centerYAnchor.constraint(equalTo: view.centerYAnchor).isActive = true
// Or
NSLayoutConstraint.activate([
alert.centerXAnchor.constraint(equalTo: view.centerXAnchor),
alert.centerYAnchor.constraint(equalTo: view.centerYAnchor),
])
This is using auto layout to position your views, and the views will properly update when the trait collection changes.

Answer 2

When adding a view programmatically the view doesn't adjust according to the screen rotation because you have fixed the view height, width so after rotation you need to again give its frame.
This doesn't happen when you use constraints to add a view either programmatically or from the storyboard
For your alert to resize you have to again give its frame in viewDidLayoutSubviews()
override func viewDidLayoutSubviews() {
YourAlertView.frame = CGRect(x:0 , y: 0,width: self.view.frame.width, height: self.view.frame.height )
}
Works like a charm for me.