Swift constraint doesnot change in Autolayout while hiding views - ios

Question

These are my codes
//My UIViews
#IBOutlet weak var UIVIewFirst: UIView!
#IBOutlet weak var UIViewSecond: UIView!
#IBOutlet weak var UIViewThird: UIView!
#IBOutlet weak var middleViewHeightConstraint: NSLayoutConstraint!
#IBOutlet weak var ViewThirdHeight: NSLayoutConstraint!
There is a button to show and hide the view as;
#IBAction func infoClicked(sender: SSRadioButton) {
if UIViewSecond.hidden {
sender.selected = false
UIViewSecond.hidden = false
self.middleViewHeightConstraint.constant = 134
} else {
sender.selected = true
UIViewSecond.hidden = true
self.middleViewHeightConstraint.constant = 0
self.ViewThirdHeight.constant = 180
}
}
the vertical gap between each view is 10. After hiding the view the gap becomes 20. But i need it to set it 10 between third and second view. Even though i set the third view height constant to any number it does not changes it position.Can anyone suggest why is this happening??

Answer 1

Constraints ignore the hidden property.
If possible for your requirements, embedd your views within a UIStackView.
See this example.

Answer 2

You need to take the outlet connection of the vertical spacing constraint between either First-Second or Second-Third views. Also if you want to hide/show only Second view, you don't need to do any changes to Third View height constraint.
Say For example, we take the outlet of vertical spacing between First and Second views, then:
#IBOutlet weak var UIVIewFirst: UIView!
#IBOutlet weak var UIViewSecond: UIView!
#IBOutlet weak var middleViewHeightConstraint: NSLayoutConstraint!
#IBOutlet weak var verticalSpacingConstraint: NSLayoutConstraint!
#IBAction func infoClicked(sender: UIButton)
{
if UIViewSecond.hidden
{
sender.selected = false
UIViewSecond.hidden = false
self.middleViewHeightConstraint.constant = 134
self.verticalSpacingConstraint.constant = 10
}
else
{
sender.selected = true
UIViewSecond.hidden = true
self.middleViewHeightConstraint.constant = 0
self.verticalSpacingConstraint.constant = 0
}
}
Below are the screenshots of output:
1. When button is not selected
2. When button is selected

Answer 3

You have not tell your view to update the view with the new constraint, you have to call this code:
self.view.layoutIfNeeded()

Answer 4

firstView
| gap = 10
secondView
| gap = 10
thirdView
after removing secondView
firstView
| gap = 10
---------- height = 0
| gap = 10
thirdView
so the gap becomes 20
try to add constraint programmatically after hiding the view or decrease any one gap.

Answer 5

Try to change the frame of the view instead of changing the constraint, also do view.layoutIfNeeded after making any changes.