Custom Modal transition not working - example - ios

Question

I am trying to get UIViewControllerContextTransitioning working.
What I want:
What I would like to have, is presenting modal view controller with custom animation and transparent background.
Wthat I did:
I created animator implementing UIViewControllerTransitioningDelegate,
Set for modal controller:
self.modalPresentationStyle = UIModalPresentationCustom;
self.transitioningDelegate = self;
What I achieved so far,
Modal controller animates presenting and dismissing view correctly, but after dismissing is finished, entire app becomes black. I used xCode tool to pick what's in window hierarchy, and there is nothing. My guess is, that I changed VC's superview when adding to context's container.
Animator
#implementation AlertAnimator
const static CGFloat kAnimationDuration = 1.2;
- (void)animateTransition:(id<UIViewControllerContextTransitioning>)transitionContext {
UIViewController *to = [transitionContext viewControllerForKey:UITransitionContextToViewControllerKey];
UIViewController *from = [transitionContext viewControllerForKey:UITransitionContextFromViewControllerKey];
if (self.transitionType == ModalAnimatedTransitioningTypePresent) {
[self animatePresentingInContext:transitionContext toVC:to fromVC:from];
} else if (self.transitionType == ModalAnimatedTransitioningTypeDismiss) {
[self animateDismissingInContext:transitionContext toVC:to fromVC:from];
}
}
- (NSTimeInterval)transitionDuration:(id<UIViewControllerContextTransitioning>)transitionContext{
return kAnimationDuration;
}
- (void)animatePresentingInContext:(id<UIViewControllerContextTransitioning>)transitionContext toVC:(UIViewController *)toVC fromVC:(UIViewController *)fromVC {
CGRect fromVCRect = [transitionContext initialFrameForViewController:fromVC];
CGRect toVCRect = fromVCRect;
toVCRect.origin.y = toVCRect.size.height;
toVC.view.frame = toVCRect;
UIView *container = [transitionContext containerView];
[container addSubview:fromVC.view];
[container addSubview:toVC.view];
[UIView animateWithDuration:kAnimationDuration animations:^{
toVC.view.frame = fromVCRect;
} completion:^(BOOL finished) {
[transitionContext completeTransition:![transitionContext transitionWasCancelled]];
}];
}
- (void)animateDismissingInContext:(id<UIViewControllerContextTransitioning>)transitionContext toVC:(UIViewController *)toVC fromVC:(UIViewController *)fromVC {
CGRect fromVCRect = [transitionContext initialFrameForViewController:fromVC];
fromVCRect.origin.y = fromVCRect.size.height;
UIView *container = [transitionContext containerView];
[container addSubview:toVC.view];
[container addSubview:fromVC.view];
[UIView animateWithDuration:kAnimationDuration animations:^{
fromVC.view.frame = fromVCRect;
} completion:^(BOOL finished) {
[transitionContext completeTransition:![transitionContext transitionWasCancelled]];
}];
}
#end
Code example:
https://www.dropbox.com/s/oaghtgwvga4nxs4/Test.zip?dl=0
Question:
What I am doing wrong and why screen becomes black?

Answer 1

if this is a presenting animator you should not add the fromVC.view as a subview because its already there. This will cause it to bug out. Try it out and tell me what happens. If its a dismissal animator you shouldn't add the presentingViewController to the hierarchy either.