swift: show animation after returning in ViewController - ios

Question

I have first ViewController and second ViewController. When I return to first ViewController from second ViewController after that I want to show buttons in first ViewController.
To returning I use this code:
self.dismiss(animated: true, completion: nil)
And this code to show buttons in first ViewController
#IBOutlet weak var infoButton: UIButton!
#IBOutlet weak var nextButton: UIButton!
#IBOutlet weak var infoButtonTopConstraint: NSLayoutConstraint!
#IBOutlet weak var nextButtonBottomConstraint: NSLayoutConstraint!
#IBOutlet weak var infoButtonHeightConstraint: NSLayoutConstraint!
#IBOutlet weak var nextButtonHeightConstraint: NSLayoutConstraint!
override func viewWillAppear(_ animated: Bool) {
super.viewWillAppear(true)
showButtonAnimation()
//animaton()
}
func showButtonAnimation() {
self.infoButtonTopConstraint.constant += self.infoButtonHeightConstraint.constant
self.nextButtonBottomConstraint.constant -= self.nextButtonHeightConstraint.constant
UIView.animate(withDuration: 1.0, delay: 0.0,
options: [], animations: {
self.view.layoutIfNeeded()
})
}
But buttons not showing when I return from second ViewController.

Answer 1

Replace this
func showButtonAnimation() {
self.view.layoutIfNeeded()
UIView.animate(withDuration: 1.0, delay: 0.0,
options: [], animations: {
self.infoButtonTopConstraint.constant += self.infoButtonHeightConstraint.constant
self.nextButtonBottomConstraint.constant -= self.nextButtonHeightConstraint.constant
self.view.layoutIfNeeded()
})
}
EDIT 1
viewWillAppear not getting called reason : you are presenting 2nd viewController as overCurrentContext modalPresentationStyle.
Just replace overCurrentContext with fullScreen and it works.

Answer 2

Whenever you call viewWillAppear keep in mind that view where not loaded in main view so animation will not work proper. You should use a viewDidAppear.
override func viewDidAppear(_ animated: Bool) {
super.viewDidAppear(animated)
showButtonAnimation()
}
And in your animation method update as below because you change constraint value inside animation block that in need to out of it.
func showButtonAnimation() {
self.infoButtonTopConstraint.constant += self.infoButtonHeightConstraint.constant
self.nextButtonBottomConstraint.constant -= self.nextButtonHeightConstraint.constant
UIView.animate(withDuration: 1.0, delay: 0.0,
options: [], animations: {
self.view.layoutIfNeeded()
})
}

Answer 3

I have tried your code and it is working for the first time, but the problem might be every time the constant value of the button constraint are increased.
so they might be hiding behind your main view.
Solution:- you can take flag and change its value when animation is completed.
Now when you come back from the second controller then you have to check in the viewWillAppear that if the buttons are visible or not, if they are visible then you do not have to call the showButtonAnimation method.
You can see where the buttons are in current screen with clicking on
button to see the UI hierarchy.
Hope this will solve your issue.

Answer 4

You can add a delegate in your second viewController. like:
protocol SecondViewControllerDelegate {
func vcDismissed()
}
Class SecondViewController : UIViewController {
weak var delegate: SecondViewControllerDelegate
.....
//Where you are dismissing your viewController, call the delegate method in completion.
func someMethod() {
self.dismiss(animated: true, completion: {
self.delegate.vcDismissed()
})
}
}
Now in your FirstViewController, conform the protocol and implement the method like below:
extension FirstViewController: SecondViewControllerDelegate {
func vcDismissed() {
//Here call your showButton method
self.showButton()
}
}
And do not forget to set the delegate when your are creating the instance of your secondViewController where you are presenting it. like
objSecondViewController.delegate = self
Hope this helps. for any query feel free to leave a comment.