How can I show a hidden UIButton? - ios

Question

Views were placed using code.
If I press deleteButton (button), I want the hidden button(imgButton) to appear.
However, imgView's width is not refresh.
MainViewController.swift
import UIKit
class MainViewController: UIViewController {
var trashIsSelected: Bool!
let imgButton: UIButton = {
let imgView = UIButton()
imgView.setImage(UIImage(named: "schedule_delete_icon"), for: UIControlState.normal)
// imgView.imageView?.image = UIImage(named: "schedule_delete_icon")
imgView.translatesAutoresizingMaskIntoConstraints = false
return imgView
}()
let deleteButton: UIButton = {
let imgBtn = UIButton()
imgBtn.setImage(UIImage(named: "icon_delete"), for: UIControlState.normal)
// imgBtn.imageView?.image = UIImage(named: "icon_delete")
imgBtn.translatesAutoresizingMaskIntoConstraints = false
return imgBtn
}()
let label: UILabel = {
let label = UILabel()
label.translatesAutoresizingMaskIntoConstraints = false
label.text = "하ㅣㅇ하이히아히아하하하하ㅏㅎ하ㅏㅎ하ㅏ하하하하ㅏㅏ하하하하하ㅏ"
return label
}()
var imgViewWidth: NSLayoutConstraint!
override func viewDidLoad() {
super.viewDidLoad()
setupLayout()
}
func setupLayout(){
let testView = UIScrollView()
self.view.addSubview(testView)
testView.backgroundColor = .lightGray
testView.translatesAutoresizingMaskIntoConstraints = false
testView.leadingAnchor.constraint(equalTo: self.view.leadingAnchor).isActive = true
testView.trailingAnchor.constraint(equalTo: self.view.trailingAnchor).isActive = true
testView.topAnchor.constraint(equalTo: self.view.safeAreaLayoutGuide.topAnchor).isActive = true
testView.heightAnchor.constraint(equalTo: self.view.heightAnchor, multiplier: 0.3).isActive = true
testView.addSubview(imgButton)
testView.addSubview(label)
imgButton.leadingAnchor.constraint(equalTo: testView.leadingAnchor, constant: 10).isActive = true
imgButton.centerYAnchor.constraint(equalTo: testView.centerYAnchor).isActive = true
imgButton.heightAnchor.constraint(equalTo: testView.heightAnchor, multiplier: 0.2).isActive = true
imgButton.widthAnchor.constraint(equalTo: imgButton.heightAnchor, multiplier: 0).isActive = true
imgButton.isHidden = true
trashIsSelected = false
label.centerYAnchor.constraint(equalTo: testView.centerYAnchor).isActive = true
label.leadingAnchor.constraint(equalTo: imgButton.trailingAnchor, constant: 10).isActive = true
label.heightAnchor.constraint(equalTo: testView.heightAnchor, multiplier: 0.2).isActive = true
label.widthAnchor.constraint(equalTo: testView.widthAnchor, multiplier: 0.5).isActive = true
self.view.addSubview(deleteButton)
deleteButton.leadingAnchor.constraint(equalTo: self.view.leadingAnchor).isActive = true
deleteButton.bottomAnchor.constraint(equalTo: self.view.bottomAnchor).isActive = true
deleteButton.addTarget(self, action: #selector(self.addBtnAction(_:)), for: UIControlEvents.touchUpInside)
}
#objc func addBtnAction(_ sender: UIButton){
print("hi")
if trashIsSelected == false{
trashIsSelected = true
imgButton.isHidden = false
imgButton.widthAnchor.constraint(equalToConstant: 50).isActive = true
imgButton.updateConstraints()
}else{
trashIsSelected = false
imgButton.widthAnchor.constraint(equalToConstant: 0).isActive = true
imgButton.isHidden = true
imgButton.updateConstraints()
}
}
}
This is error message:
2018-05-23 14:00:47.697959+0900 Test[67488:4887863] [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.
(
"",
""
)
Will attempt to recover by breaking constraint
Make a symbolic breakpoint at UIViewAlertForUnsatisfiableConstraints to catch this in the debugger.
The methods in the UIConstraintBasedLayoutDebugging category on UIView listed in may also be helpful.

Answer 1

You are adding new constraints to the button that conflict with the old ones (how can a button be 0 points wide, and simultaneously 50 points wide?). To make it work, you need to turn off the old constraint before you activate a new one. I recommend creating a property that would keep the current imgButton constraint at all times, and then when you want to change it, just use that (either turn it off and create a new one, or just set a constant, which in your case is better and easier):
import UIKit
class MainViewController: UIViewController {
// property referencing current imgButton width constraint
fileprivate var imgButtonWidthConstraint: NSLayoutConstraint!
var trashIsSelected: Bool!
let imgButton: UIButton = {
let imgView = UIButton()
imgView.setImage(UIImage(named: "schedule_delete_icon"), for: UIControlState.normal)
// imgView.imageView?.image = UIImage(named: "schedule_delete_icon")
imgView.translatesAutoresizingMaskIntoConstraints = false
return imgView
}()
let deleteButton: UIButton = {
let imgBtn = UIButton()
imgBtn.setImage(UIImage(named: "icon_delete"), for: UIControlState.normal)
// imgBtn.imageView?.image = UIImage(named: "icon_delete")
imgBtn.translatesAutoresizingMaskIntoConstraints = false
return imgBtn
}()
let label: UILabel = {
let label = UILabel()
label.translatesAutoresizingMaskIntoConstraints = false
label.text = "하ㅣㅇ하이히아히아하하하하ㅏㅎ하ㅏㅎ하ㅏ하하하하ㅏㅏ하하하하하ㅏ"
return label
}()
var imgViewWidth: NSLayoutConstraint!
override func viewDidLoad() {
super.viewDidLoad()
setupLayout()
}
func setupLayout(){
let testView = UIScrollView()
self.view.addSubview(testView)
testView.backgroundColor = .lightGray
testView.translatesAutoresizingMaskIntoConstraints = false
testView.leadingAnchor.constraint(equalTo: self.view.leadingAnchor).isActive = true
testView.trailingAnchor.constraint(equalTo: self.view.trailingAnchor).isActive = true
testView.topAnchor.constraint(equalTo: self.view.safeAreaLayoutGuide.topAnchor).isActive = true
testView.heightAnchor.constraint(equalTo: self.view.heightAnchor, multiplier: 0.3).isActive = true
testView.addSubview(imgButton)
testView.addSubview(label)
imgButton.leadingAnchor.constraint(equalTo: testView.leadingAnchor, constant: 10).isActive = true
imgButton.centerYAnchor.constraint(equalTo: testView.centerYAnchor).isActive = true
imgButton.heightAnchor.constraint(equalTo: testView.heightAnchor, multiplier: 0.2).isActive = true
// keep the reference to constraint that defines width
// (we will use the constraint setting the width to constant, since then you can
// simply switch the constant between 0 and 50):
imgButtonWidthConstraint = imgButton.widthAnchor.constraint(equalToConstant: 0)
imgButtonWidthConstraint.isActive = true
imgButton.isHidden = true
trashIsSelected = false
label.centerYAnchor.constraint(equalTo: testView.centerYAnchor).isActive = true
label.leadingAnchor.constraint(equalTo: imgButton.trailingAnchor, constant: 10).isActive = true
label.heightAnchor.constraint(equalTo: testView.heightAnchor, multiplier: 0.2).isActive = true
label.widthAnchor.constraint(equalTo: testView.widthAnchor, multiplier: 0.5).isActive = true
self.view.addSubview(deleteButton)
deleteButton.leadingAnchor.constraint(equalTo: self.view.leadingAnchor).isActive = true
deleteButton.bottomAnchor.constraint(equalTo: self.view.bottomAnchor).isActive = true
deleteButton.addTarget(self, action: #selector(self.addBtnAction(_:)), for: UIControlEvents.touchUpInside)
}
#objc func addBtnAction(_ sender: UIButton){
print("hi")
if trashIsSelected == false{
trashIsSelected = true
imgButton.isHidden = false
// just change the constant to what you want
imgButtonWidthConstraint.constant = 50
imgButton.updateConstraints()
} else {
trashIsSelected = false
imgButtonWidthConstraint.constant = 0
imgButton.isHidden = true
imgButton.updateConstraints()
}
}
}
EDIT:
Just for completeness of the answer, if you were for some reason using constraints where changing a constant would not be enough, you would have to activate and deactivate the constraints. E.g., if you were using multiplier to determine imgButton's width, you would have to use this approach (multiplier is an immutable property of the NSLayoutConstraint). So therefore creating a constraint:
// simply switch the constant between 0 and 50):
imgButtonWidthConstraint = imgButton.widthAnchor.constraint(equalTo: someOtherView.widthAnchor, multiplier: 0)
imgButtonWidthConstraint.isActive = true
And then in addBtnAction you would have to do to this:
#objc func addBtnAction(_ sender: UIButton){
print("hi")
if trashIsSelected == false{
trashIsSelected = true
imgButton.isHidden = false
// first deactivate current constraint
imgButtonWidthConstraint.isActive = false
// then create a new one and store it to imgButtonWidthConstraint property (the old one is deactivated, so you don't need a reference to it anymore)
imgButtonWidthConstraint = imgButton.widthAnchor.constraint(equalTo: someOtherView.widthAnchor, multiplier: 0.75)
// and activate the new one
imgButtonWidthConstraint.isActive = true
imgButton.updateConstraints()
} else {
trashIsSelected = false
// same process again
imgButtonWidthConstraint.isActive = false
imgButtonWidthConstraint = imgButton.widthAnchor.constraint(equalTo: someOtherView.widthAnchor, multiplier: 0)
imgButtonWidthConstraint.isActive = true
imgButton.isHidden = true
imgButton.updateConstraints()
}
}