Back animation of UIButton doesn't work - ios

Question

I have a text view (textView) and a button (sendButton).
The button's bottom constraint is constraint to the view's bottom.
The textView becomes the first responder in viewDidAppear.
So when i present the Controller, the keyboard goes up and the button animates along with it.
Here's the code:
override func viewDidLoad() {
super.viewDidLoad()
setupSendButton()
dismissKeyboard()
}
override func viewDidAppear(_ animated: Bool) {
textView.becomeFirstResponder()
}
func setupSendButton() {
self.view.addSubview(sendButton)
sendButton.leadingAnchor.constraint(equalTo: self.view.leadingAnchor).isActive = true
sendButton.trailingAnchor.constraint(equalTo: self.view.trailingAnchor).isActive = true
sendButton.heightAnchor.constraint(equalToConstant: 60).isActive = true
sendButton.bottomAnchor.constraint(equalTo: self.view.bottomAnchor).isActive = true
sendButton.translatesAutoresizingMaskIntoConstraints = false
}
// TextView Delegate Method
func textViewDidBeginEditing(_ textView: UITextView) {
// Animation begins after textView did begin editing
animateSendButton(bottomConstraint: -216)
}
At this point everything works fine.
My problem is that when i dismiss the keyboard and end editing, I want to animate back so that the button's bottom constraint is the view's bottom constraint again.
But that doesn't work.
// TextView Delegate Method
func textViewDidEndEditing(_ textView: UITextView) {
// Animation begins after textView did end editing (it doesn't)
animateSendButton(bottomConstraint: 0)
}
// function to dismiss keyboard and end editing
func dismissKeyboard() {
let touch = UITapGestureRecognizer(target: self, action: #selector(tapGesture))
self.view.addGestureRecognizer(touch)
}
#objc func tapGesture(gesture: UITapGestureRecognizer){
// Ends editing and dismisses keyboard
self.view.endEditing(true)
}
Animate Button Funktion: animateSendButton(bottomConstraint: CGFloat)
func animateSendButton(bottomConstraint: CGFloat) {
sendButton.bottomAnchor.constraint(equalTo: self.view.bottomAnchor, constant: bottomConstraint).isActive = true
UIView.animate(withDuration: 0.55, delay: 0, usingSpringWithDamping: 1, initialSpringVelocity: 1, options: .curveEaseIn, animations: {
self.view.layoutIfNeeded()
}, completion: nil)
}

Answer 1

You must delete previous bottom constraint before of adding other
or change
var bottomCon:NSLayoutConstraint!
//////
func setupSendButton() {
self.view.addSubview(sendButton)
sendButton.leadingAnchor.constraint(equalTo: self.view.leadingAnchor).isActive = true
sendButton.trailingAnchor.constraint(equalTo: self.view.trailingAnchor).isActive = true
sendButton.heightAnchor.constraint(equalToConstant: 60).isActive = true
self.bottomCon = sendButton.bottomAnchor.constraint(equalTo: self.view.bottomAnchor)
self.bottomCon.active= true
sendButton.translatesAutoresizingMaskIntoConstraints = false
}
func animateSendButton(bottomConstraint: CGFloat) {
self.bottomCon.constant = bottomConstraint
UIView.animate(withDuration: 0.55, delay: 0, usingSpringWithDamping: 1, initialSpringVelocity: 1, options: .curveEaseIn, animations: {
self.view.layoutIfNeeded()
}, completion: nil)
}