I've looked around for an answer for this and spent the last two hours pulling my hair out to no end.
I'm implementing a very basic custom view controller transition animation, which simply zooms in on the presenting view controller and grows in the presented view controller. It adds a fade effect (0 to 1 alpha and visa versa).
It works fine when presenting the view controller, however when dismissing, it brings the presenting view controller back in all the way to fill the screen, but then it inexplicably disappears. I'm not doing anything after these animations to alter the alpha or the hidden values, it's pretty much a fresh project. I've been developing iOS applications for 3 years so I suspect this may be a bug, unless someone can find out where I'm going wrong.
class FadeAndGrowAnimationController : NSObject, UIViewControllerAnimatedTransitioning, UIViewControllerTransitioningDelegate {
func animationControllerForPresentedController(presented: UIViewController!, presentingController presenting: UIViewController!, sourceController source: UIViewController!) -> UIViewControllerAnimatedTransitioning! {
return self
}
func animationControllerForDismissedController(dismissed: UIViewController!) -> UIViewControllerAnimatedTransitioning! {
return self
}
func transitionDuration(transitionContext: UIViewControllerContextTransitioning!) -> NSTimeInterval {
return 2
}
func animateTransition(transitionContext: UIViewControllerContextTransitioning!) {
let fromViewController = transitionContext.viewControllerForKey(UITransitionContextFromViewControllerKey) as UIViewController
let toViewController = transitionContext.viewControllerForKey(UITransitionContextToViewControllerKey) as UIViewController
toViewController.view.transform = CGAffineTransformMakeScale(0.5, 0.5)
toViewController.view.alpha = 0
transitionContext.containerView().addSubview(fromViewController.view)
transitionContext.containerView().addSubview(toViewController.view)
transitionContext.containerView().bringSubviewToFront(toViewController.view)
UIView.animateWithDuration(self.transitionDuration(transitionContext), animations: {
fromViewController.view.transform = CGAffineTransformScale(fromViewController.view.transform, 2, 2)
fromViewController.view.alpha = 1
toViewController.view.transform = CGAffineTransformMakeScale(1, 1)
toViewController.view.alpha = 1
}, completion: { finished in
transitionContext.completeTransition(!transitionContext.transitionWasCancelled())
})
}
}
And the code to present:
let targetViewController = self.storyboard.instantiateViewControllerWithIdentifier("Level1ViewController") as Level1ViewController
let td = FadeAndGrowAnimationController()
targetViewController.transitioningDelegate = td
targetViewController.modalPresentationStyle = .Custom
self.presentViewController(targetViewController, animated: true, completion: nil)
As you can see, a fairly basic animation. Am I missing something here? Like I said, it presents perfectly fine, then dismisses 99.99% perfectly fine, yet the view controller underneath after the dismissal is inexplicably removed. The iPad shows a blank screen - totally black - after this happens.
