heightAnchor.constraint not change height of view

Question

I use this code:

func show(){
    view.translatesAutoresizingMaskIntoConstraints = false
    view.leftAnchor.constraint(equalTo: view.leftAnchor, constant: 0).isActive = true
    view.topAnchor.constraint(equalTo: view.topAnchor, constant: 0).isActive = true
    view.heightAnchor.constraint(equalToConstant: view.frame.height - 300).isActive = true
    view.rightAnchor.constraint(equalTo: view.rightAnchor, constant: 0).isActive = true
}

func hide(){
    view.translatesAutoresizingMaskIntoConstraints = false
    view.leftAnchor.constraint(equalTo: view.leftAnchor, constant: 0).isActive = true
    view.topAnchor.constraint(equalTo: view.topAnchor, constant: 0).isActive = true
    view.heightAnchor.constraint(equalToConstant: view.frame.height + 300).isActive = true
    view.rightAnchor.constraint(equalTo: view.rightAnchor, constant: 0).isActive = true
}

show function works fine, but hide function does not work and heightAnchor does not work.

I use this code for delete : `view.translatesAutoresizingMaskIntoConstraints = false` — Mohammad, Dec 12 '18 at 09:29
no that code doesn't delete your previous setup constraint.it just turn off autolayout engine — andesta.erfan, Dec 12 '18 at 09:29
use this `view.removeConstraints(constraints: [NSLayoutConstraint][NSLayoutConstraint])` to delete all constraint that you want — andesta.erfan, Dec 12 '18 at 09:31
This will help - https://stackoverflow.com/questions/52042162/constraints-not-updating-when-keyboard-appears/52043090#52043090 — Rakesha Shastri, Dec 12 '18 at 09:31
@andesta.erfan i get this error `Cannot convert value of type '(NSLayoutConstraint).Type' to expected argument type 'NSLayoutConstraint'` — Mohammad, Dec 12 '18 at 09:33
I use this : `view.removeConstraints(view.constraints)`. and this code remove all children constraints — Mohammad, Dec 12 '18 at 09:39

Bozzo · Accepted Answer · 2018-12-12T09:52:28.557

First declare constraints

var heightArchonWhenShow = view.heightAnchor.constraint(equalToConstant: view.frame.height - 300)
var heightArchonWhenHide = view.heightAnchor.constraint(equalToConstant: view.frame.height + 300)

After init your constraints on ViewDidLoad

func setConstraints(){
    view.translatesAutoresizingMaskIntoConstraints = false
    view.leftAnchor.constraint(equalTo: view.leftAnchor, constant: 0).isActive = true
    view.topAnchor.constraint(equalTo: view.topAnchor, constant: 0).isActive = true
    view.rightAnchor.constraint(equalTo: view.rightAnchor, constant: 0).isActive = true
    heightArchonWhenShow.isActive = true
}

And simple active them , don't overwrite. Like this:

func show(){
    heightArchonWhenShow.isActive = true
    heightArchonWhenHide.isActive = false
}

func hide(){
    heightArchonWhenShow.isActive = false
    heightArchonWhenHide.isActive = true
}

If u want u can also animate changes, like that :

func hide(){
    heightArchonWhenShow.isActive = false
    heightArchonWhenHide.isActive = true

    UIView.animate(withDuration: 0.3) {
        self.view.layoutIfNeeded()
    }
}

Best answer , Thank you so much. – reza_khalafi Jul 05 '20 at 11:38 — reza_khalafi, Jul 05 '20 at 11:38

Francesco Destino · Answer 2 · 2018-12-12T09:59:09.637

2

I recommend you to setup your constraint in a different function like maybe setup() and store them in some variable that you can modify after, I'll show you an example

var constraint: NSLayoutConstraint?

func setup() {
    constraint = view.heightAnchor.constraint(equalToConstant: view.frame.height)
}

func show() {
    if constraint != nil {
        constraint!.constant = constraint!.constant + 300
    }
}

func hide() {
    if constraint != nil {
        constraint!.constant = constraint!.constant - 300
    }
}

edited Dec 12 '18 at 09:59

answered Dec 12 '18 at 09:39

Francesco Destino

343
1
14

This wont even compile >:( – J. Doe Dec 12 '18 at 09:56
I made some edits, i did some mistakes before sorry :) But i saw the other answer, it's better and more detailed :D – Francesco Destino Dec 12 '18 at 09:59

score 2 · Answer 3 · answered Dec 12 '18 at 10:24

You need only 1 var

var heightCon = view.heightAnchor.constraint(equalToConstant: view.frame.height - 300)
heightCon.isActive = true

Then manage it's constant value

func showOrHide(_ te:Bool){

   heightCon.constant = te ? view.frame.height - 300 : view.frame.height + 300

     UIView.animate(withDuration: 0.3) {
        self.view.layoutIfNeeded()
    }
}

heightAnchor.constraint not change height of view

3 Answers3

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