How to hide and unhide a view with height in swift?

Question

I am trying to hide and unhide a view. Its size should be 0 when it is hidden and about 200 when it is unhidden. I have two view controllers. When the first controller shows the view is hidden for the first time and its size is set to 0 and then it navigates to other controller and takes some values from the textfeilds and display them on a tableview in previous controller.

Now, I am able to hide the view for the first time with height 0 but when I take up the values the view is still hidden.

This is the code I have tried so far:

mainView.isHidden == true
mainView.heightAnchor.constraint(equalToConstant: CGFloat(0)).isActive = true

// when I get the values but this code doesn't work
    mainView.isHidden == false
    mainView.heightAnchor.constraint(equalToConstant: CGFloat(100)).isActive = true

Any help would be appreciated.

You need to update the height. Currently, you are assigning the new constraint. Check this: https://stackoverflow.com/a/49776158/14733292 — Raja Kishan, Jan 23 '21 at 08:36
I have tried that it isn't working. It only works when I don't give any height when the view is hidden. — LetUsDevelop, Jan 23 '21 at 08:39

score 2 · Answer 1 · answered Jan 23 '21 at 10:06

class viewController: UIViewController {

     var height: NSLayoutConstraint!

     override func viewDidLoad() {
         super.viewDidLoad()
         
         height = mainView.heightAnch.constraint(equalToConstant: 0)
         height.isActive = true

         //handle change height
         if mainView.isHidden == true {
             height.constant = 0
         }
         else {
             height.constant = 200
         }
     }
}

score 0 · Answer 2 · answered Jan 23 '21 at 09:02

You have two options. The first method set identifier to height constraint

set identifier:

then find and change with below code:

// first option
        // find own constraint with indentifier
        if let heightConstraint = self.myView.constraints.first(where: { item -> Bool in
            return item.identifier == "heightIdentifier"
        }) {
            
            // set any constant to constraint
            heightConstraint.constant = 200.0 // for hidden
            heightConstraint.constant = 0.0 // for hide
            
            // any work
            
        }

second option: set IBOutlet to target constraint:

@IBOutlet weak var heightConstraint: NSLayoutConstraint!

then change direct and simple:

// second option
// change constant direct
self.heightConstraint.constant = 200.0 // for hidden
self.heightConstraint.constant = 0.0 // for hide
            
// any work

score 0 · Answer 3 · answered Jan 23 '21 at 12:30

You keep both created constraints in your view controller and activate however you need accordingly, using isActive property of NSLayoutConstraint:

var hiddenHeightConstraint: NSLayoutConstraint?
var showingHeightConstraint: NSLayoutConstraint?

var isMainViewHidden: Bool = false {
    didSet {
        mainView.isHidden == isMainViewHidden
        hiddenHeightConstraint?.isActive = isMainViewHidden
        showingHeightConstraint?.isActive = !isMainViewHidden
        
        // Don't forget to call layoutIfNeeded() when you messing with the constraints
        view.layoutIfNeeded()
    }
}

override func viewDidLoad() {
    super.viewDidLoad()
    
    hiddenHeightConstraint = mainView.heightAnchor.constraint(equalToConstant: CGFloat(0))
    showingHeightConstraint = mainView.heightAnchor.constraint(equalToConstant: CGFloat(100))
    
    isMainViewHidden = false
}

How to hide and unhide a view with height in swift?

3 Answers3