How to get a fade out animation while dismissing a view controller - ios

Question

I have an Image view in my View Controller. I want to dismiss the view controller when a Pan gesture is recognized towards the down side of the view controller. While I have achieved dismiss the view controller with a Pan gesture, I am trying to figure out how can I add an animation before dismissing just like as in the Photos application in the iPhone.
-(void)addPanGesture{
UIPanGestureRecognizer *gestureRecognizer = [[UIPanGestureRecognizer alloc] initWithTarget:self action:#selector(dismissViewGes:)];
gestureRecognizer.delegate = self;
[self.view addGestureRecognizer:gestureRecognizer];
}
-(void)dismissViewGes:(UIPanGestureRecognizer *)gesture {
CGPoint velocity = [gesture velocityInView:self.view];
if(velocity.y > 0)
{
CATransition *transition = [[CATransition alloc]init];
transition.duration = 2;
[transition setValue:[NSNumber numberWithFloat:0.5f] forKey:kCATransitionFade];
transition.subtype = kCATransitionFromTop;
[self.view.layer addAnimation:transition forKey:nil];
[[NetWrapper shared] addRemovedController:self];
[self dismissViewControllerAnimated:NO completion:nil];
}
}
I tried adding a CATransition hoping that the fade out animation will work but it is not working, the view dismisses as soon as the pan gesture is applied.
How can i add in a fade out while with the view dismissing just like in the photos application.

Answer 1

Try this:
#IBAction func clickDismiss(_ sender: Any) {
let transition: CATransition = CATransition()
transition.duration = 0.5
transition.timingFunction = CAMediaTimingFunction(name: kCAMediaTimingFunctionEaseInEaseOut)
transition.type = kCATransitionFade
transition.subtype = kCATransitionFromBottom
self.view.window!.layer.add(transition, forKey: nil)
self.dismiss(animated: false, completion: nil)
}
I present a SubViewController and add a UIButton on it. Add those codes to The button click event and It's work for me.

Answer 2

Swift 4.2, iOS 11
Here is an elegant way using extensions:
extension CATransition {
func fadeTransition() -> CATransition {
let transition = CATransition()
transition.duration = 0.4
transition.type = CATransitionType.fade
transition.subtype = CATransitionSubtype.fromRight
return transition
}
}
Then you can just write these three lines of code in a function or inside the action button in your UIViewController:
private func dismissVC() {
let transition = CATransition().fadeTransition()
navigationController?.view.layer.add(transition, forKey: kCATransition)
navigationController?.popViewController(animated: false)
}

Answer 3

If you need to add animation on presenting or dismissing a ViewController you should use UIViewControllerAnimatedTransitioning, there's a similar answer here:
How do I do a Fade/No transition between view controllers
If you need it to be interactive, you can use UIPercentDrivenInteractiveTransition, which is a class that controls the transition in percentages.
About all this there's a great sample code from Apple:
https://developer.apple.com/library/content/samplecode/CustomTransitions/Introduction/Intro.html
It's a little old but it's simple.