Unable to simultaneously satisfy constraints when animating constraint - ios

Question

This is my code:
class AvailableTrainScene: UIView {
let seeMoreButton: UIButton = {
let v = UIButton()
v.translatesAutoresizingMaskIntoConstraints = false
v.backgroundColor = .blue
v.layer.cornerRadius = 20
v.setTitle("Voir Plus", for: .normal)
return v
}()
var seeMoreBottom: NSLayoutConstraint?
override init(frame: CGRect) {
super.init(frame: frame)
addSubview(seeMoreButton)
}
required init?(coder aDecoder: NSCoder) {
super.init(coder: aDecoder)
}
override func layoutSubviews() {
NSLayoutConstraint.activate([
seeMoreButton.heightAnchor.constraint(equalToConstant: 40),
seeMoreButton.widthAnchor.constraint(equalTo: widthAnchor, multiplier: 0.8),
seeMoreButton.centerXAnchor.constraint(equalTo: centerXAnchor)
])
seeMoreBottom = seeMoreButton.bottomAnchor.constraint(equalTo: bottomAnchor, constant: -8)
seeMoreBottom?.isActive = false
}
func hideSeeMore(_ hide: Bool) {
if hide {
seeMoreBottom?.constant = 40
}else{
seeMoreBottom?.constant = -8
}
UIView.animate(withDuration: 0.4, delay: 0, usingSpringWithDamping: 0.6, initialSpringVelocity: 4, options: .curveEaseOut, animations: {
self.layoutIfNeeded()
}, completion: nil)
}
}
i get this error when animating using the function hideSeeMore:
LayoutConstraints] Unable to simultaneously satisfy constraints.
Probably at least one of the constraints in the following list is one you don't want.
Try this:
(1) look at each constraint and try to figure out which you don't expect;
(2) find the code that added the unwanted constraint or constraints and fix it.
(
"<NSLayoutConstraint:0x28060dc70 UIButton:0x105534920'Voir Plus'.bottom == DzTrain_2_0.AvailableTrainScene:0x1055300d0.bottom - 8 (active)>",
"<NSLayoutConstraint:0x2806894a0 UIButton:0x105534920'Voir Plus'.bottom == DzTrain_2_0.AvailableTrainScene:0x1055300d0.bottom + 40 (active)>"
)
Will attempt to recover by breaking constraint
<NSLayoutConstraint:0x2806894a0 UIButton:0x105534920'Voir Plus'.bottom == DzTrain_2_0.AvailableTrainScene:0x1055300d0.bottom + 40 (active)>
Make a symbolic breakpoint at UIViewAlertForUnsatisfiableConstraints to catch this in the debugger.
The methods in the UIConstraintBasedLayoutDebugging category on UIView listed in <UIKitCore/UIView.h> may also be helpful.
i tried to add tow constraints one to hide and another to show (priority is deferent) then activate/deactivate them but nothing happend?
Someone have this before?

Answer 1

Put constraints in
override init(frame: CGRect) {
super.init(frame: frame)
addSubview(seeMoreButton)
NSLayoutConstraint.activate([
seeMoreButton.heightAnchor.constraint(equalToConstant: 40),
seeMoreButton.widthAnchor.constraint(equalTo: widthAnchor, multiplier: 0.8),
seeMoreButton.centerXAnchor.constraint(equalTo: centerXAnchor)
])
seeMoreBottom = seeMoreButton.bottomAnchor.constraint(equalTo: bottomAnchor, constant: -8)
seeMoreBottom?.isActive = false
}
as this
override func layoutSubviews()
is called for any
self.layoutIfNeeded()
which causes your edit in constant to conflict with a new overwrite here
seeMoreBottom = seeMoreButton.bottomAnchor.constraint(equalTo: bottomAnchor, constant: -8)
seeMoreBottom?.isActive = false