I have a View Controller with a view hierarchy within two nested views that are placed with autolayout constraints.
I then place in code some UIViews into one of those views but I don't want to use constraints for these as the user can drag them around.
If the device gets rotated, or the user splits the view using the slide over functionality of the iPad I want to reset the locations of these UIViews into their new place based on the automatic layout of the parent views:
I have a function in the questionView called resetAnswerPosition() that correctly positions all of the Views based on the position of the reference View after the auto-layout positioning has kicked in. QuestionView has stores a reference to the ReferenceView, to make this easier.
The documentation suggests using viewWillTransitionToSize & willTransitionToTraitCollection to run these changes which works for rotation, or for when the slide over changes the aspect ratio from landscape to portrait or back again. However on an iPad Pro when change the split from 2/3 to 1/2 the aspect ratio isn't changing that the resetAnswerTilesPositions is being called before the Reference View has been resized.
I have also tried to use the viewDidLayoutSubViews but again have the issue that this is run before the Reference view has been resized.
override func viewWillTransitionToSize(size: CGSize, withTransitionCoordinator coordinator: UIViewControllerTransitionCoordinator) {
super.viewWillTransitionToSize(size, withTransitionCoordinator: coordinator)
coordinator.animateAlongsideTransition({ (context) -> Void in
self.questionView.resetAnswerTilePositions()
},
completion: { (context) -> Void in
})
}
override func willTransitionToTraitCollection(newCollection: UITraitCollection, withTransitionCoordinator coordinator: UIViewControllerTransitionCoordinator) {
self.questionView.resetAnswerTilePositions()
}
override func viewDidLayoutSubviews() {
super.viewDidLayoutSubviews()
self.questionAnswerView.resetAnswerTilePositions()
}
What function can I register either with the View Controller or the QuestionView which will only be called once all of the views have been laid out according to the updated constraints?
As always posting a question led me to the right answer.
In the Question View you can override the layoutSubviews routine which is really nice from a separation of concerns of point of view. Only the Question View then needs to know how to layout its own subviews.
override func layoutSubviews() {
super.layoutSubviews()
self.resetAnswerTilePositions()
}
Related
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?
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.
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.
When testing my app on an iPad using multitasking and I change the app size on the app, the collection view cells need to be resized or else they don't fit in the view window.
I have took some measures such as
detecting device to change the size of the cells
measure view size to make sure cells fit within the window
Add an observer if user changes device orientation
This is all great but however when actually changing the window size when using multitasking, or going back to the full screen app, the cell sizes don't change and look out of place. This is until forced by switching orientation or switching view controllers so viewWillLoad or viewDidLoad gets executed again.
So how can I set a notification if the view.frame size changes ?
I think the right function to override is viewWillTransition(to:, with:). It is called whenever the container size is about to change.
override func viewWillTransition(to size: CGSize, with coordinator: UIViewControllerTransitionCoordinator) {
super.viewWillTransition(to: size, with: coordinator)
self.collectionView?.collectionViewLayout.invalidateLayout()
}
I think you are over complicating the issue, just use the following so when the device is rotated or resized the collection view also changes accordingly.
override func viewWillLayoutSubviews() {
super.viewWillLayoutSubviews()
guard let collectionLayout = collectionView.collectionViewLayout as? UICollectionViewFlowLayout else {
return
}
if UIApplication.shared.statusBarOrientation == UIInterfaceOrientation.landscapeLeft ||
UIApplication.shared.statusBarOrientation == UIInterfaceOrientation.landscapeRight {
//here you can do the logic for the cell size if phone is in landscape
} else {
//logic if not landscape
}
collectionLayout.invalidateLayout()
}
I tried RileyDev answer but the app entered in an infinite loop.
There is no delegate that is executed just when the App's window bounds change, so I've made my own version of the viewWillTransition(to size and traitCollectionDidChange.
With the code below you can detect the window bounds resizing change even if the traits don't change, and resize your collection view cells accordingly invalidating the collection view layout.
var previousWindowBounds: CGRect?
override func viewWillLayoutSubviews() {
super.viewWillLayoutSubviews()
if let currentBounds = view.window?.bounds,
let previousWindowBounds = previousWindowBounds, currentBounds != previousWindowBounds {
collectionView?.collectionViewLayout.invalidateLayout()
}
previousWindowBounds = view.window?.bounds
}
I'm working on this project and I have one scene on the Storyboard.
The scene is a TableViewController.
The table view have a custom prototype cell (linked to CustomCell.swift).
Inside the prototype cell there's a label and a custom UIView (linked to CustomView.swift). These elements have layout constraints relative to the contentView of the prototype cell.
Now, I want the stuff being drawn on my custom view to change when the size of the view changes, so that when the device rotates it is adjusted to that new cell width. Because of the constraints, the frame of CustomView will change when the CustomCell changes size, after the device is rotated. In order to detect this, I added two property observers to CustomView.swift:
override var frame: CGRect {
didSet {
print("Frame was set!")
updateDrawing()
}
}
override var bounds: CGRect {
didSet {
print("Bounds were set!")
updateDrawing()
}
}
When running the project, the second observer works fine when I rotate the device. The first observer does not. My question is why does the first observer not detect that the frame has changed?
.frame is computed from the .bounds and the .center of the view (and the transform), so it does not change. In order to react to rotation override this (starting from iOS8):
override func viewWillTransitionToSize(size: CGSize, withTransitionCoordinator coordinator: UIViewControllerTransitionCoordinator) {
super.viewWillTransitionToSize(size, withTransitionCoordinator: coordinator)
coordinator.animateAlongsideTransition({ (coordinator) -> Void in
// do your stuff here
// here the frame has the new size
}, completion: nil)
}
I've built detail view in Interface Builder showing informations and photos about some object. Because lenght of informations and number of photos will vary, all is nested in UIScrollView.
Photos are shown in UICollectionView, but I need to always show all contained photos, so I disabled scrolling and dynamically changing Height constraint of UICollectionView by this function (called when finishing rendering cells):
func resizePhotosCollectionView() {
photosCollectionViewHeightConstraint.constant = photosCollectionView.collectionViewLayout.collectionViewContentSize()
}
It works great until this UICollectionView needs resize (typically by device orientation change). I am trying to use UIViewControllerTransitionCoordinator in function:
override func viewWillTransitionToSize(size: CGSize, withTransitionCoordinator coordinator: UIViewControllerTransitionCoordinator) {
coordinator.animateAlongsideTransition(nil) { context in
self.resizePhotosCollectionView()
}
super.viewWillTransitionToSize(size, withTransitionCoordinator: coordinator)
}
but result is jerky because Height constraint changed after transition is complete.
Is there any way how to automatically resize UICollectionView after view transition? If not, how to animate Height constraint change during transition?
Using Xcode 6.1 for target IOS 8.
If I recall correctly, you need to layout the view immediately.
override func viewWillTransitionToSize(size: CGSize, withTransitionCoordinator coordinator: UIViewControllerTransitionCoordinator) {
coordinator.animateAlongsideTransition(nil) { context in
self.resizePhotosCollectionView()
self.view.setNeedsLayout()
self.view.layoutIfNeeded()
}
super.viewWillTransitionToSize(size, withTransitionCoordinator: coordinator)
}
Have you tried wrapping your constraint update into a view animation?
photosCollectionViewHeightConstraint.constant =
photosCollectionView.collectionViewLayout.collectionViewContentSize()
photosCollectionView.setNeedsUpdateConstraints()
UIView.animateWithDuration(0.3, animations: { () -> Void in
photosCollectionView.layoutIfNeeded()
})
I am looking for a way to enforce a UIPopoverPresentationController automatically resize to fill most of the screen, minus say 50 units of padding.
I first tried settings the preferredContentSize in viewDidLoad, and then detect when rotation occurs and update that CGSize to the new size I could calculate. But for some reason, this isn't working in my context. I was using UIDeviceOrientationDidChangeNotification which normally calls the method, but it's not called when the popover exists within a photo editing extension.
I am wondering if there's any other way to change the popover size besides manually updating the preferredContentSize after detecting a size change? If not, is there a way to detect rotation from within this popover in this context?
Try this:
func isLandscape() -> Bool {
// your logical here
}
override func viewWillTransition(to size: CGSize, with coordinator: UIViewControllerTransitionCoordinator) {
let myNewSize = isLandscape() ? mySizeLandscape : mySizePortrait
self.preferredContentSize = myNewSize
super.viewWillTransition(to: myNewSize, with: coordinator)
}