Disable autorotate on a single subview in iOS8 - ios

Question

I'm writing a drawing app and I don't want the drawing view to rotate. At the same time, I want other controls to rotate nicely depending on the orientation of the device. In iOS 7 I've solved this via:
- (void)willAnimateRotationToInterfaceOrientation:(UIInterfaceOrientation)toInterfaceOrientation duration:(NSTimeInterval)duration {
float rotation;
if (toInterfaceOrientation==UIInterfaceOrientationPortrait) {
rotation = 0;
}
else if (toInterfaceOrientation==UIInterfaceOrientationLandscapeLeft) {
rotation = M_PI/2;
} else if (toInterfaceOrientation==UIInterfaceOrientationLandscapeRight) {
rotation = -M_PI/2;
}
self.drawingView.transform = CGAffineTransformMakeRotation(rotation);
self.drawingView.frame = self.view.frame;
}
But on iOS 8 even though the function is called and the transform is set correctly, it does not prevent the view from rotating.
I've tried creating a view controller which simply prevents the rotation of it's view and add it's view to the view hierarchy, but then it doesn't respond to user input.
Any ideas?
Thanks!

Answer 1

Okay after some fighting with subviews and transitionCoordinators I've finally figured it out:
- (void)viewWillTransitionToSize:(CGSize)size withTransitionCoordinator:(id<UIViewControllerTransitionCoordinator>)coordinator {
CGAffineTransform targetRotation = [coordinator targetTransform];
CGAffineTransform inverseRotation = CGAffineTransformInvert(targetRotation);
[coordinator animateAlongsideTransition:^(id<UIViewControllerTransitionCoordinatorContext> context) {
self.drawingView.transform = CGAffineTransformConcat(self.drawingView.transform, inverseRotation);
self.drawingView.frame = self.view.bounds;
} completion:^(id<UIViewControllerTransitionCoordinatorContext> context) {
}];
}
What I do is, I calculate the inverse of the transform applied to the view and then use it to change the transform. furthermore I change the frame with the view bounds. This is due to it being full screen.

Answer 2

Dimitri's answer worked perfectly for me. This is the swift version of the code in case someone needs it...
override func viewWillTransitionToSize(size: CGSize, withTransitionCoordinator coordinator: UIViewControllerTransitionCoordinator) {
let targetRotation = coordinator.targetTransform()
let inverseRotation = CGAffineTransformInvert(targetRotation)
coordinator.animateAlongsideTransition({ context in
self.drawingView.transform = CGAffineTransformConcat(self.drawingView.transform, inverseRotation)
self.drawingView.frame = self.view.bounds
context.viewControllerForKey(UITransitionContextFromViewControllerKey)
}, completion: nil)
}

Answer 3

Swift 4 has a lot of updates, including the viewWillTransition function.
override func viewWillTransition(to size: CGSize, with coordinator: UIViewControllerTransitionCoordinator) {
super.viewWillTransition(to: size, with: coordinator)
let targetRotation = coordinator.targetTransform
let inverseRotation = targetRotation.inverted()
coordinator.animate(alongsideTransition: { context in
self.drawingView.transform = self.drawingView.transform.concatenating(inverseRotation)
self.drawingView.frame = self.view.bounds
context.viewController(forKey: UITransitionContextViewControllerKey.from)
}, completion: nil)
}

Answer 4

I managed to obtain this, check:
rotation working as desired
Note: The green and the red views are subviews of the controller's view. The blue view is subview of the red view.
Idea
According to https://developer.apple.com/library/archive/qa/qa1890/_index.html, we need to apply an inverse rotation to the view when it is transitioning to a new size.
In addition to that, we need to adjust the constraints after rotation (landscape/portrait).
Implementation
class MyViewController: UIViewController {
var viewThatShouldNotRotate = UIView()
var view2 = UIView()
var insiderView = UIView()
var portraitConstraints: [NSLayoutConstraint]!
var landscapeConstraints: [NSLayoutConstraint]!
override func viewDidLoad() {
super.viewDidLoad()
viewThatShouldNotRotate.backgroundColor = .red
view2.backgroundColor = .green
insiderView.backgroundColor = .blue
view.addSubview(viewThatShouldNotRotate)
view.addSubview(view2)
viewThatShouldNotRotate.addSubview(insiderView)
portraitConstraints = createConstraintsForPortrait()
landscapeConstraints = createConstraintsForLandscape()
}
func createConstraintsForLandscape() -> [NSLayoutConstraint] {
return NSLayoutConstraint.autoCreateConstraintsWithoutInstalling {
viewThatShouldNotRotate.autoMatch(.height, to: .width, of: view)
viewThatShouldNotRotate.autoMatch(.width, to: .height, of: view)
viewThatShouldNotRotate.autoCenterInSuperview()
view2.autoPinEdgesToSuperviewEdges(with: UIEdgeInsets(), excludingEdge: .top)
view2.autoSetDimension(.height, toSize: 100)
insiderView.autoPinEdges(toSuperviewMarginsExcludingEdge: .bottom)
insiderView.autoSetDimension(.height, toSize: 100)
}
}
func createConstraintsForPortrait() -> [NSLayoutConstraint] {
return NSLayoutConstraint.autoCreateConstraintsWithoutInstalling {
viewThatShouldNotRotate.autoMatch(.height, to: .height, of: view)
viewThatShouldNotRotate.autoMatch(.width, to: .width, of: view)
viewThatShouldNotRotate.autoCenterInSuperview()
view2.autoPinEdges(toSuperviewMarginsExcludingEdge: .top)
view2.autoSetDimension(.height, toSize: 100)
insiderView.autoPinEdges(toSuperviewMarginsExcludingEdge: .bottom)
insiderView.autoSetDimension(.height, toSize: 100)
}
}
override func viewDidLayoutSubviews() {
super.viewDidLayoutSubviews()
if view.bounds.size.width > view.bounds.size.height {
// landscape
portraitConstraints.forEach {$0.autoRemove()}
landscapeConstraints.forEach { $0.autoInstall() }
} else {
landscapeConstraints.forEach {$0.autoRemove()}
portraitConstraints.forEach { $0.autoInstall() }
}
}
override func viewWillTransition(to size: CGSize, with coordinator: UIViewControllerTransitionCoordinator) {
super.viewWillTransition(to: size, with: coordinator)
let viewToRotate: UIView = viewThatShouldNotRotate
coordinator.animate(alongsideTransition: { (UIViewControllerTransitionCoordinatorContext) -> Void in
let deltaTransform = coordinator.targetTransform
let deltaAngle = atan2f(Float(deltaTransform.b), Float(deltaTransform.a))
var currentRotation = (viewToRotate.layer.value(forKeyPath: "transform.rotation.z") as! NSNumber).floatValue
// Adding a small value to the rotation angle forces the animation to occur in a the desired direction, preventing an issue where the view would appear to rotate 2PI radians during a rotation from LandscapeRight -> LandscapeLeft.
currentRotation = currentRotation + (-1 * Float(deltaAngle)) + 0.0001
viewToRotate.layer.setValue(currentRotation, forKeyPath:"transform.rotation.z")
}) { (UIViewControllerTransitionCoordinatorContext) -> Void in
var currentTransform = viewToRotate.transform;
currentTransform.a = round(currentTransform.a);
currentTransform.b = round(currentTransform.b);
currentTransform.c = round(currentTransform.c);
currentTransform.d = round(currentTransform.d);
viewToRotate.transform = currentTransform;
}
}
}

Answer 5

In iOS 8 transforms aren't applied to individual views owned by view controllers. Instead the rotation transforms are applied to the UIWindow. The result is that developers never see a rotation being applied, but rather a resize.
In iOS 8 you can either override the callbacks for size class changes and perform your own transform there, or you can get the orientation events as described here: https://developer.apple.com/library/prerelease/ios/documentation/EventHandling/Conceptual/EventHandlingiPhoneOS/motion_event_basics/motion_event_basics.html.