Create background color change animation - swift

I am trying to create an animation where I change the color of a rectangle from orange to blue. Here is where I created the rectangle and set its background color to orange:
let colorView = UIView(frame: CGRect(x: 250, y: 500, width: 75, height: 75))
colorView.backgroundColor = UIColor.orange
and here is where I add the animation with the function definition of the animation below it
let colorChangeAnimation = constructColorChangeAnimation()
colorView.layer.add(colorChangeAnimation, forKey: "color")
private func constructColorChangeAnimation() -> CABasicAnimation {
let ColorChangeAnimation = CABasicAnimation(keyPath: "backgroundColor")
ColorChangeAnimation.fromValue = UIColor.orange
ColorChangeAnimation.toValue = UIColor.blue
return ColorChangeAnimation
}
This implementation doesn't seem to work and I'm not sure what it is I need to change. The documentation says that the fromValue and toValue should be the way to change the animation but it just doesn't seem to want to work. (also fyi I did originally have a duration variable for the animation function but it also wasn't working then)

you should use UIColor.orange.cgColor
animation.fromValue = UIColor.orange.cgColor
animation.duration = 3
and UIView animation is much easier
colorView.backgroundColor = UIColor.orange
UIView.animate(withDuration: 3) {
self.aview.backgroundColor = UIColor.blue
}

Try this one;
let colourAnim = CABasicAnimation(keyPath: "backgroundColor")
colourAnim.fromValue = self.colorView.backgroundColor
colourAnim.toValue = UIColor.blue.cgColor
colourAnim.duration = 1.0
self.colorView.addAnimation(colourAnim, forKey: "colourAnimation")
self.colorView.backgroundColor = UIColor.blue.cgColor
You should set the background color of the view after the animation and use o .cgColor

Use UIView.animate like this:
Under your class controller declare view and button (in my example I add corner radius for more cute result)
let chamgeButton = UIButton(type: .system)
let orangeView = UIView()
in viewDidLoad construct them, present and add constraints:
orangeView.backgroundColor = .orange
orangeView.layer.cornerRadius = 8
orangeView.clipsToBounds = true
orangeView.translatesAutoresizingMaskIntoConstraints = false
chamgeButton.backgroundColor = .red
chamgeButton.setTitle("changeColor", for: .normal)
chamgeButton.setTitleColor(.white, for: .normal)
chamgeButton.layer.cornerRadius = 8
chamgeButton.clipsToBounds = true
chamgeButton.addTarget(self, action: #selector(handleChangeColor), for: .touchUpInside)
chamgeButton.translatesAutoresizingMaskIntoConstraints = false
view.addSubview(orangeView)
orangeView.heightAnchor.constraint(equalToConstant: 200).isActive = true
orangeView.widthAnchor.constraint(equalToConstant: 200).isActive = true
orangeView.centerYAnchor.constraint(equalTo: view.centerYAnchor).isActive = true
orangeView.centerXAnchor.constraint(equalTo: view.centerXAnchor).isActive = true
view.addSubview(chamgeButton)
chamgeButton.bottomAnchor.constraint(equalTo: view.safeAreaLayoutGuide.bottomAnchor, constant: -10).isActive = true
chamgeButton.trailingAnchor.constraint(equalTo: view.trailingAnchor, constant: -10).isActive = true
chamgeButton.leadingAnchor.constraint(equalTo: view.leadingAnchor, constant: 10).isActive = true
chamgeButton.heightAnchor.constraint(equalToConstant: 50).isActive = true
now add the target button function to change color:
#objc fileprivate func handleChangeColor() {
UIView.animate(withDuration: 0.3, delay: 0, options: .curveEaseOut, animations: {
self.orangeView.backgroundColor = .blue
self.view.layoutIfNeeded()
}, completion: nil)
}
This is the result:

Related

func is reseting position of pan gesture

The func addBlackView is adding a black view everytime the func is called. The black view is connected a to uiPangesture the problem is evertyime the func addblackview is called the code is reseting the position of wherever the first black has been moved. You can see what is goin on in the gif below. I just want the 1st black view to not move and stay in the same position if a new black view is Called.
import UIKit
class ViewController: UIViewController {
var image1Width2: NSLayoutConstraint!
var iHieght: NSLayoutConstraint!
var currentView = UIView()
override func viewDidLoad() {
super.viewDidLoad()
view.addSubview(currentView)
view.addSubview(button)
button.translatesAutoresizingMaskIntoConstraints = false
NSLayoutConstraint.activate([
button.trailingAnchor.constraint(equalTo: view.trailingAnchor, constant: -16),
button.topAnchor.constraint(equalTo: view.safeAreaLayoutGuide.topAnchor, constant: 16),
button.widthAnchor.constraint(equalToConstant: 100),
button.heightAnchor.constraint(equalToConstant: 80),
])
button.addTarget(self,action: #selector(addBlackView),for: .touchUpInside)
}
let slider:UISlider = {
let slider = UISlider(frame: .zero)
return slider
}()
private lazy var button: UIButton = {
let button = UIButton()
button.backgroundColor = .blue
button.setTitleColor(.white, for: .normal)
button.setTitle("add", for: .normal)
return button
}()
let blackView: UIView = {
let view = UIView()
view.backgroundColor = .black
return view
}()
var count = 0
#objc
private func addBlackView() {
let newBlackView = UIView(frame: CGRect(x: 20, y: 20, width: 100, height: 100)) // whatever frame you want
newBlackView.backgroundColor = .orange
self.view.addSubview(newBlackView)
self.currentView = newBlackView
let recognizer = UIPanGestureRecognizer(target: self, action: #selector(moveView(_:)))
newBlackView.addGestureRecognizer(recognizer)
newBlackView.isUserInteractionEnabled = true
image1Width2 = newBlackView.widthAnchor.constraint(equalTo: view.widthAnchor, multiplier: 0.1)
image1Width2.isActive = true
iHieght = newBlackView.heightAnchor.constraint(equalTo: view.heightAnchor, multiplier: 0.1)
iHieght.isActive = true
count += 1
newBlackView.tag = (count)
newBlackView.translatesAutoresizingMaskIntoConstraints = false
newBlackView.centerYAnchor.constraint(equalTo: view.centerYAnchor).isActive = true
newBlackView.centerXAnchor.constraint(equalTo: view.centerXAnchor).isActive = true
}
#objc private func moveView(_ recognizer: UIPanGestureRecognizer) {
switch recognizer.state {
case .changed:
let translation = recognizer.translation(in: self.view)
recognizer.view!.center = .init(x: recognizer.view!.center.x + translation.x,
y: recognizer.view!.center.y + translation.y)
recognizer.setTranslation(.zero, in: self.view)
default:
break
}
}
}
They always go back to the centre because you have constrained the black (orange) views to the centre:
newBlackView.centerYAnchor.constraint(equalTo: view.centerYAnchor).isActive = true
newBlackView.centerXAnchor.constraint(equalTo: view.centerXAnchor).isActive = true
You shouldn't even be able to drag any of the views at all, but I guess setting center ignores constraints for some reason. Anyway, when you add a new view, UIKit calls view.setNeedsLayout/layoutIfNeeded somewhere down the line, and this causes all the views to realise "oh wait, I'm supposed to be constrained to the centre!" and snap back. :D
If you want to keep using constraints, try storing the centre X and Y constraints of all the views in an array:
var centerXConstraints: [NSLayoutConstraint] = []
var centerYConstraints: [NSLayoutConstraint] = []
And append to them when you add a new view:
let yConstraint = newBlackView.centerYAnchor.constraint(equalTo: view.centerYAnchor)
let xConstraint = newBlackView.centerXAnchor.constraint(equalTo: view.centerXAnchor)
xConstraint.isActive = true
yConstraint.isActive = true
centerXConstraints.append(xConstraint)
centerYConstraints.append(yConstraint)
Then, rather than changing the center, change the constant of these constraints:
let centerXConstraint = centerXConstraints[recognizer.view!.tag - 1]
let centerYConstraint = centerYConstraints[recognizer.view!.tag - 1]
centerXConstraint.constant += translation.x
centerYConstraint.constant += translation.y
Alternatively, and this is what I would do, just remove all your constraints, and translateAutoresizingMaskIntoConstraints = true. This way you can freely set your center.

add 2 image views to a uiscrollview func every time it is called

My swift code below goal is to add 2 image views every time. Ass you can in the gif below only one image view is being added. I just need to add 2 image views. The image views are lastImage and lastImage2. you can see only lastImage is being shown. It seems I can only add 1 imageview when func didclickadd is called.
import UIKit
class ViewController: UIViewController {
fileprivate var lastImage:UIImageView?
fileprivate var lastImage2:UIImageView?
fileprivate var mainViewBootom:NSLayoutConstraint?
override func viewDidLoad() {
super.viewDidLoad()
view.backgroundColor = .white
setupVIew()
}
override func viewDidAppear(_ animated: Bool) {
scrollView.contentSize = CGSize(width: view.frame.width, height: mainView.frame.height)
view.layoutIfNeeded()
}
//MARK: Components
let scrollView:UIScrollView = {
let sv = UIScrollView(frame: .zero)
return sv
}()
let mainView:UIView = {
let uv = UIView()
uv.backgroundColor = .white
return uv
}()
let btnAdd:UIButton = {
let btn = UIButton(type: .system)
btn.setTitle("Add", for: .normal)
return btn
}()
let textField:UITextField = {
let jake = UITextField()
return jake
}()
//MARK: Setup UI
func setupVIew() {
view.addSubview(scrollView)
view.addSubview(btnAdd)
view.addSubview(textField)
scrollView.translatesAutoresizingMaskIntoConstraints = false
btnAdd.translatesAutoresizingMaskIntoConstraints = false
textField.translatesAutoresizingMaskIntoConstraints = false
NSLayoutConstraint.activate([
btnAdd.centerXAnchor.constraint(equalTo: view.centerXAnchor),
btnAdd.bottomAnchor.constraint(equalTo: view.safeAreaLayoutGuide.bottomAnchor, constant: -12),
btnAdd.widthAnchor.constraint(equalToConstant: 100),
btnAdd.heightAnchor.constraint(equalToConstant: 45),
//
textField.centerXAnchor.constraint(equalTo: view.centerXAnchor),
textField.bottomAnchor.constraint(equalTo: view.safeAreaLayoutGuide.bottomAnchor, constant: 25),
textField.widthAnchor.constraint(equalToConstant: 100),
textField.heightAnchor.constraint(equalToConstant: 45),
//
scrollView.leadingAnchor.constraint(equalTo: view.leadingAnchor),
scrollView.trailingAnchor.constraint(equalTo: view.trailingAnchor),
scrollView.topAnchor.constraint(equalTo: view.safeAreaLayoutGuide.topAnchor),
scrollView.bottomAnchor.constraint(equalTo: btnAdd.topAnchor , constant: -12),
])
btnAdd.addTarget(self, action: #selector(didClickedAdd), for: .touchUpInside)
scrollView.addSubview(mainView)
mainView.translatesAutoresizingMaskIntoConstraints = false
NSLayoutConstraint.activate([
mainView.leadingAnchor.constraint(equalTo: view.leadingAnchor),
mainView.trailingAnchor.constraint(equalTo: view.trailingAnchor),
mainView.topAnchor.constraint(equalTo: scrollView.topAnchor),
])
let imgView = UIImageView(frame: CGRect(x: 0, y: 0, width: 150, height: 100))
imgView.backgroundColor = .red
mainView.addSubview(imgView)
let samsam = UIImageView(frame: CGRect(x: 0, y: 200, width: 40, height: 100))
samsam.backgroundColor = .blue
mainView.addSubview(samsam)
imgView.translatesAutoresizingMaskIntoConstraints = false
imgView.centerXAnchor.constraint(equalTo: view.centerXAnchor).isActive = true
imgView.widthAnchor.constraint(equalToConstant: 150).isActive = true
imgView.heightAnchor.constraint(equalToConstant: 100).isActive = true
samsam.translatesAutoresizingMaskIntoConstraints = false
samsam.centerXAnchor.constraint(equalTo: view.centerXAnchor).isActive = true
samsam.topAnchor.constraint(equalTo: imgView.bottomAnchor).isActive = true
samsam.widthAnchor.constraint(equalToConstant: 75).isActive = true
samsam.heightAnchor.constraint(equalToConstant: 100).isActive = true
if lastImage != nil {
imgView.topAnchor.constraint(equalTo: lastImage!.bottomAnchor , constant: 20).isActive = true
}else{
imgView.topAnchor.constraint(equalTo: mainView.topAnchor , constant: 12).isActive = true
}
lastImage = samsam
mainViewBootom = mainView.bottomAnchor.constraint(equalTo: lastImage!.bottomAnchor , constant: 12)
mainViewBootom!.isActive = true
}
#objc func didClickedAdd(){
let imgView = UIImageView(frame: CGRect(x: 20, y: 0, width: 30, height: 20))
imgView.backgroundColor = .orange
mainView.addSubview(imgView)
let ss = UIImageView(frame: CGRect(x: 0, y: 0, width: 40, height: 50))
imgView.backgroundColor = .green
mainView.addSubview(ss)
imgView.translatesAutoresizingMaskIntoConstraints = false
imgView.centerXAnchor.constraint(equalTo: view.centerXAnchor).isActive = true
imgView.widthAnchor.constraint(equalToConstant: 40).isActive = true
imgView.heightAnchor.constraint(equalToConstant: 60).isActive = true
ss.translatesAutoresizingMaskIntoConstraints = false
ss.leadingAnchor.constraint(equalTo: view.leadingAnchor).isActive = false
ss.widthAnchor.constraint(equalToConstant: 80).isActive = true
ss.heightAnchor.constraint(equalToConstant: 90).isActive = true
if lastImage != nil {
ss.topAnchor.constraint(equalTo: imgView.topAnchor , constant: 20).isActive = true
imgView.topAnchor.constraint(equalTo: lastImage!.bottomAnchor , constant: 50).isActive = true
}else{
imgView.topAnchor.constraint(equalTo: mainView.topAnchor , constant: 10).isActive = true
ss.bottomAnchor.constraint(equalTo: imgView.bottomAnchor , constant: 25).isActive = true
}
lastImage = imgView
lastImage2 = ss
mainView.removeConstraint(mainViewBootom!)
mainViewBootom = mainView.bottomAnchor.constraint(equalTo: lastImage2!.bottomAnchor , constant: 40)
mainViewBootom!.isActive = true
view.layoutIfNeeded()
scrollView.contentSize = CGSize(width: view.frame.width, height: mainView.frame.height)
view.layoutIfNeeded()
}
}
Couple notes...
With proper constraint setup, auto-layout handles the UIScrollView content size all by itself. No need to ever set scrollView.contentSize = ...
You have several instances of adding a subview (image view) to your mainView, which is a subview of your scroll view, but then you add constraints from that subview to your controller's view. Make sure you are constraining elements to the proper other elements.
Here's your code, with commented changes:
class BenViewController: UIViewController {
fileprivate var lastImage:UIImageView?
// 1) don't need this
// fileprivate var lastImage2:UIImageView?
fileprivate var mainViewBootom:NSLayoutConstraint?
override func viewDidLoad() {
super.viewDidLoad()
view.backgroundColor = .white
setupVIew()
}
// 2) don't need this
// override func viewDidAppear(_ animated: Bool) {
// scrollView.contentSize = CGSize(width: view.frame.width, height: mainView.frame.height)
// view.layoutIfNeeded()
// }
//MARK: Components
let scrollView:UIScrollView = {
let sv = UIScrollView(frame: .zero)
return sv
}()
let mainView:UIView = {
let uv = UIView()
uv.backgroundColor = .white
return uv
}()
let btnAdd:UIButton = {
let btn = UIButton(type: .system)
btn.setTitle("Add", for: .normal)
return btn
}()
let textField:UITextField = {
let jake = UITextField()
return jake
}()
//MARK: Setup UI
func setupVIew() {
view.addSubview(scrollView)
view.addSubview(btnAdd)
view.addSubview(textField)
scrollView.translatesAutoresizingMaskIntoConstraints = false
btnAdd.translatesAutoresizingMaskIntoConstraints = false
textField.translatesAutoresizingMaskIntoConstraints = false
NSLayoutConstraint.activate([
btnAdd.centerXAnchor.constraint(equalTo: view.centerXAnchor),
btnAdd.bottomAnchor.constraint(equalTo: view.safeAreaLayoutGuide.bottomAnchor, constant: -12),
btnAdd.widthAnchor.constraint(equalToConstant: 100),
btnAdd.heightAnchor.constraint(equalToConstant: 45),
//
textField.centerXAnchor.constraint(equalTo: view.centerXAnchor),
textField.bottomAnchor.constraint(equalTo: view.safeAreaLayoutGuide.bottomAnchor, constant: 25),
textField.widthAnchor.constraint(equalToConstant: 100),
textField.heightAnchor.constraint(equalToConstant: 45),
//
scrollView.leadingAnchor.constraint(equalTo: view.leadingAnchor),
scrollView.trailingAnchor.constraint(equalTo: view.trailingAnchor),
scrollView.topAnchor.constraint(equalTo: view.safeAreaLayoutGuide.topAnchor),
scrollView.bottomAnchor.constraint(equalTo: btnAdd.topAnchor , constant: -12),
])
btnAdd.addTarget(self, action: #selector(didClickedAdd), for: .touchUpInside)
scrollView.addSubview(mainView)
mainView.translatesAutoresizingMaskIntoConstraints = false
// 3) change this:
// NSLayoutConstraint.activate([
// mainView.leadingAnchor.constraint(equalTo: view.leadingAnchor),
// mainView.trailingAnchor.constraint(equalTo: view.trailingAnchor),
// mainView.topAnchor.constraint(equalTo: scrollView.topAnchor),
// ])
//
// to this
NSLayoutConstraint.activate([
mainView.leadingAnchor.constraint(equalTo: scrollView.leadingAnchor),
mainView.trailingAnchor.constraint(equalTo: scrollView.trailingAnchor),
mainView.topAnchor.constraint(equalTo: scrollView.topAnchor),
mainView.bottomAnchor.constraint(equalTo: scrollView.bottomAnchor),
mainView.widthAnchor.constraint(equalTo: scrollView.widthAnchor),
])
// end of change 3)
let imgView = UIImageView(frame: CGRect(x: 0, y: 0, width: 150, height: 100))
imgView.backgroundColor = .red
mainView.addSubview(imgView)
let samsam = UIImageView(frame: CGRect(x: 0, y: 200, width: 40, height: 100))
samsam.backgroundColor = .blue
mainView.addSubview(samsam)
imgView.translatesAutoresizingMaskIntoConstraints = false
// 4) change view.centerXAnchor to mainView.centerXAnchor
// imgView.centerXAnchor.constraint(equalTo: view.centerXAnchor).isActive = true
imgView.centerXAnchor.constraint(equalTo: mainView.centerXAnchor).isActive = true
imgView.widthAnchor.constraint(equalToConstant: 150).isActive = true
imgView.heightAnchor.constraint(equalToConstant: 100).isActive = true
samsam.translatesAutoresizingMaskIntoConstraints = false
// 5) change view.centerXAnchor to mainView.centerXAnchor
// samsam.centerXAnchor.constraint(equalTo: view.centerXAnchor).isActive = true
samsam.centerXAnchor.constraint(equalTo: mainView.centerXAnchor).isActive = true
samsam.topAnchor.constraint(equalTo: imgView.bottomAnchor).isActive = true
samsam.widthAnchor.constraint(equalToConstant: 75).isActive = true
samsam.heightAnchor.constraint(equalToConstant: 100).isActive = true
if lastImage != nil {
imgView.topAnchor.constraint(equalTo: lastImage!.bottomAnchor , constant: 20).isActive = true
}else{
imgView.topAnchor.constraint(equalTo: mainView.topAnchor , constant: 12).isActive = true
}
lastImage = samsam
mainViewBootom = mainView.bottomAnchor.constraint(equalTo: lastImage!.bottomAnchor , constant: 12)
mainViewBootom!.isActive = true
}
#objc func didClickedAdd(){
let imgView = UIImageView(frame: CGRect(x: 20, y: 0, width: 30, height: 20))
imgView.backgroundColor = .orange
mainView.addSubview(imgView)
let ss = UIImageView(frame: CGRect(x: 0, y: 0, width: 40, height: 50))
// 6) typo or copy/paste mistake
// imgView.backgroundColor = .green
ss.backgroundColor = .green
mainView.addSubview(ss)
imgView.translatesAutoresizingMaskIntoConstraints = false
// 7) change view.centerXAnchor to mainView.centerXAnchor
// imgView.centerXAnchor.constraint(equalTo: view.centerXAnchor).isActive = true
imgView.centerXAnchor.constraint(equalTo: mainView.centerXAnchor).isActive = true
imgView.widthAnchor.constraint(equalToConstant: 40).isActive = true
imgView.heightAnchor.constraint(equalToConstant: 60).isActive = true
ss.translatesAutoresizingMaskIntoConstraints = false
// 8) change view.leadingAnchor to mainView.leadingAnchor
// ss.leadingAnchor.constraint(equalTo: view.leadingAnchor).isActive = false
ss.leadingAnchor.constraint(equalTo: mainView.leadingAnchor).isActive = false
ss.widthAnchor.constraint(equalToConstant: 80).isActive = true
ss.heightAnchor.constraint(equalToConstant: 90).isActive = true
// 9) always need to do this ... but did you mean imgView.bottomAnchor?
ss.topAnchor.constraint(equalTo: imgView.topAnchor , constant: 20).isActive = true
if lastImage != nil {
// 9a) instead of only here
//ss.topAnchor.constraint(equalTo: imgView.topAnchor , constant: 20).isActive = true
imgView.topAnchor.constraint(equalTo: lastImage!.bottomAnchor , constant: 50).isActive = true
}else{
imgView.topAnchor.constraint(equalTo: mainView.topAnchor , constant: 10).isActive = true
}
// 10) always need to do this
// deactivate bottom constraint
mainViewBootom?.isActive = false
lastImage = ss
mainViewBootom = mainView.bottomAnchor.constraint(equalTo: lastImage!.bottomAnchor, constant: 40)
mainViewBootom?.isActive = true
// 11) don't need any of this
// lastImage = imgView
// lastImage2 = ss
// mainView.removeConstraint(mainViewBootom!)
//
//
// mainViewBootom = mainView.bottomAnchor.constraint(equalTo: lastImage2!.bottomAnchor , constant: 40)
//
//
//
//
// mainViewBootom!.isActive = true
// view.layoutIfNeeded()
//
// scrollView.contentSize = CGSize(width: view.frame.width, height: mainView.frame.height)
// view.layoutIfNeeded()
}
}
Use Xcode’s “view debugger” (the button is circled in red in my screen snapshot below) and you’ll see what’s going on:
Your ss view has no background color. Note, that when you created that view, you accidentally reset the imgView background color a second time rather than setting the ss.backgroundColor.
Fix that and you’ll see your both imgView and ss:
The view debugger is your best friend when trying to diagnose issues like this. Now, obviously, the green view probably isn’t where you intended it, but you should now be able to see it and diagnose that issue very easily.
All of this having been said, a few observations:
You’re making life much harder than you need to. If you just set the constraints for the scroll view and a stack view within that scroll view, you then only need to add an arranged subview. For example:
#objc func didTapButton(_ sender: UIButton) {
stackView.addArrangedSubview(randomView())
stackView.addArrangedSubview(randomView())
}
Note, once the stack view and scroll view have been set up (see below), then you don’t need to mess around with contentSize or constraints for these subviews at all (other than the widthAnchor and heightAnchor). The auto layout engine, combined with the constraints between the stack view and the scroll view, will take care of everything for you.
So, a full working example:
class ViewController: UIViewController {
let scrollView: UIScrollView = {
let scrollView = UIScrollView()
scrollView.translatesAutoresizingMaskIntoConstraints = false
return scrollView
}()
let stackView: UIStackView = {
let stackView = UIStackView()
stackView.translatesAutoresizingMaskIntoConstraints = false
stackView.axis = .vertical
stackView.alignment = .center
stackView.spacing = 10
return stackView
}()
let button: UIButton = {
let button = UIButton(type: .system)
button.translatesAutoresizingMaskIntoConstraints = false
button.setTitle("Add", for: .normal)
button.addTarget(self, action: #selector(didTapButton(_:)), for: .touchUpInside)
return button
}()
override func viewDidLoad() {
super.viewDidLoad()
configure()
}
}
// MARK: - Actions
extension ViewController {
#objc func didTapButton(_ sender: UIButton) {
stackView.addArrangedSubview(randomView())
stackView.addArrangedSubview(randomView())
}
}
// MARK: - Private utility methods
private extension ViewController {
func configure() {
view.addSubview(scrollView)
view.addSubview(button)
scrollView.addSubview(stackView)
NSLayoutConstraint.activate([
// define frame of `scrollView`
scrollView.topAnchor.constraint(equalTo: view.topAnchor),
scrollView.bottomAnchor.constraint(equalTo: button.topAnchor),
scrollView.leadingAnchor.constraint(equalTo: view.leadingAnchor),
scrollView.trailingAnchor.constraint(equalTo: view.trailingAnchor),
// define frame of `button`
button.centerXAnchor.constraint(equalTo: view.centerXAnchor),
button.bottomAnchor.constraint(equalTo: view.bottomAnchor),
// define contentSize of `scrollView` based upon size of `stackView`
stackView.topAnchor.constraint(equalTo: scrollView.contentLayoutGuide.topAnchor),
stackView.bottomAnchor.constraint(equalTo: scrollView.contentLayoutGuide.bottomAnchor),
stackView.leadingAnchor.constraint(equalTo: scrollView.contentLayoutGuide.leadingAnchor),
stackView.trailingAnchor.constraint(equalTo: scrollView.contentLayoutGuide.trailingAnchor),
// but define width of `stackView` relative to the _main view_
stackView.widthAnchor.constraint(equalTo: scrollView.frameLayoutGuide.widthAnchor)
])
button.setContentHuggingPriority(.required, for: .vertical)
}
func randomView() -> UIView {
let widthRange = view.bounds.width * 0.1 ... view.bounds.width * 0.9
let heightRange = view.bounds.width * 0.1 ... view.bounds.width * 0.25
let view = UIView()
view.translatesAutoresizingMaskIntoConstraints = false
NSLayoutConstraint.activate([
view.widthAnchor.constraint(equalToConstant: .random(in: widthRange)),
view.heightAnchor.constraint(equalToConstant: .random(in: heightRange))
])
view.backgroundColor = UIColor(red: .random(in: 0.25...1), green: .random(in: 0.25...1), blue: .random(in: 0.25...1), alpha: 1)
return view
}
}
Even better, I’d personally set up the scroll view, stack view, button, and all the associated constraints in Interface Builder, and then that hairy configure method in my example goes away completely. It’s fun to learn how to create views programmatically, but in real-world projects, it’s rarely the most productive way to do it. Do programmatic views where needed (e.g. adding arranged subviews to the stack view on the click of a button), but otherwise, for those views that should be there when you first run the app, Interface Builder is worth considering.
E.g. It dramatically reduces the amount of code above, leaving us simply with:
class ViewController: UIViewController {
#IBOutlet weak var scrollView: UIScrollView!
#IBOutlet weak var stackView: UIStackView!
#IBAction func didTapButton(_ sender: UIButton) {
stackView.addArrangedSubview(randomView())
stackView.addArrangedSubview(randomView())
}
}
// MARK: - Private utility methods
private extension ViewController {
func randomView() -> UIView { ... }
}
Clearly, it takes a while to get used to designing views and configuring constraints in IB, but it’s worth the effort. It distills our code down the the bare essentials.
In your code, you’re setting frames for these image views and then setting translatesAutoresizingMaskIntoConstraints. There’s absolutely no point in setting the frame in that case, because translatesAutoresizingMaskIntoConstraints says “ignore my frame, use constraints instead.”
I’m assuming you’re doing all of this just to become familiar with scroll views, but it’s worth noting that, especially when adding lots of image views, that the scroll view is an inherently inefficient approach.
For example, let’s say you’ve added 100 image views, but you can see only 8 at a time. Do you really want to hold all 100 image views in memory at the same time? No.
But, UITableView, which is a subclass of UIScrollView, takes care of this. You end up only keeping the currently visible image views in memory. It’s a far better approach.
This is especially true when you start using actual UIImage objects, because they require a lot of memory. We get lulled into a sense of security, looking at reasonably sized PNG/JPG assets, but when they’re loaded into memory, they’re uncompressed and require a disproportionate amount of memory.

Reposition in y-direction a custom navigationBar titleView

Using Swift5.1.3, XCode11.3, iOS13.3,
I try to reposition a custom navigationBar titleView.
Creating the custom view and adding it to my navigationBar works fine. (see code below)
Here an example: Please only consider the DarkGray NavigationBar on top with a Name-Label and a yellow round Image. The label and image shall be moved in y-direction!
The example on the left, I have successfully running. The example on the right I try to achieve. But without luck so far.
There is one missing thing I am struggling with since 4 hours.
How do I adjust the y-position (or .topAnchor constant offset) of a custom navigationBar titleView ???
The crash-message says:
'Unable to activate constraint with anchors
<NSLayoutYAxisAnchor:0x6000033ac900 "UIStackView:0x7fdcced39ea0.top"> and
<NSLayoutYAxisAnchor:0x6000033644c0 "UIView:0x7fdcd412ba20.top"> because they
have no common ancestor. Does the constraint or its anchors reference items
in different view hierarchies? That's illegal.'
Here is my code (please note the comment with the many exclamation marks - that is the y-offset trial and crash position of my code):
override func viewWillAppear(_ animated: Bool) {
super.viewWillAppear(animated)
// ...
// set up navigationItem and navigationController look and feeel
navigationController?.set_iOS12_lookAndFeel()
navigationItem.backBarButtonItem = UIBarButtonItem(title: "", style: .plain, target: nil, action: nil)
navigationItem.largeTitleDisplayMode = .always
// create NavigationBar.titleView StackView (consisting of a label and a button)
let titleStackView = UIStackView(frame: CGRect(origin: .zero, size: CGSize(width: self.view.bounds.width, height: 88.0)))
titleStackView.isUserInteractionEnabled = true
titleStackView.axis = .horizontal
titleStackView.alignment = .center
titleStackView.spacing = 10.0
// stackView label
let labelWidth: CGFloat = UIScreen.main.bounds.width - 16.0 - 10.0 - 36.0 - 16.0 // FullScreenWidth minus (Leading + Spacing + ButtonWidth + Trailing)
let label = UILabel()
label.font = AppConstants.Font.NavBar_TitleFont
label.text = self.profileName
label.textColor = .white
label.tintColor = .white
// position label
label.translatesAutoresizingMaskIntoConstraints = false
label.widthAnchor.constraint(equalToConstant: labelWidth).isActive = true
// stackView button
let buttonWidth: CGFloat = 36.0
let button = UIButton(frame: CGRect(origin: .zero, size: CGSize(width: buttonWidth, height: buttonWidth)))
button.setImage(self.profileImageView.image, for: .normal)
button.isUserInteractionEnabled = true
button.addTarget(self, action: #selector(self.callProfileBtnMethod), for: .touchUpInside)
button.frame = CGRect(x: 0, y: 0, width: 36, height: 36)
button.layer.cornerRadius = button.frame.size.width / 2
button.layer.masksToBounds = false
button.clipsToBounds = true
// position button
button.translatesAutoresizingMaskIntoConstraints = false
button.widthAnchor.constraint(equalToConstant: buttonWidth).isActive = true
button.heightAnchor.constraint(equalToConstant: buttonWidth).isActive = true
// add label and button to stackView
titleStackView.addArrangedSubview(label)
titleStackView.addArrangedSubview(button)
// position titleStackView
titleStackView.translatesAutoresizingMaskIntoConstraints = false
// !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
// !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
// !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
// Here the code crashes !!!!!!!
titleStackView.topAnchor.constraint(equalTo: self.view.topAnchor, constant: 100.0).isActive = true
// !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
// !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
// !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
// position cockpitHeaderView (equal in size and position to titleStackView)
let cockpitHeaderView = UIView(frame: CGRect(origin: .zero, size: CGSize(width: self.view.bounds.width, height: 88.0)))
cockpitHeaderView.backgroundColor = .green
cockpitHeaderView.isUserInteractionEnabled = true
cockpitHeaderView.addSubview(titleStackView)
cockpitHeaderView.leadingAnchor.constraint(equalTo: titleStackView.leadingAnchor, constant: 0.0).isActive = true
cockpitHeaderView.topAnchor.constraint(equalTo: titleStackView.topAnchor, constant: 0.0).isActive = true
cockpitHeaderView.trailingAnchor.constraint(equalTo: titleStackView.trailingAnchor, constant: 0.0).isActive = true
cockpitHeaderView.bottomAnchor.constraint(equalTo: titleStackView.bottomAnchor, constant: 0.0).isActive = true
// finally replace NavBar title by custom cockpitHeaderView
self.title = ""
self.navigationItem.titleView = cockpitHeaderView
}
How can I move the titleView correctly ???

Cannot see Buttons in UIScrollView

I was making a list in the form of scrollview in swift where the view consists of various types such as labels, button etc.
However when i added the button to the subview, they were not displayed although all other labels etc were displayed. I also tried messing around in the constraints and anchors.
On the other hand when i added the same button to self.view.addsubview instead of scrollview.addsubview, they were displayed just not scrolling since not a part of the scrollview anymore.
I even removed the label to make sure that the buttons were not being overlapped(didn't work either)
I also tried to see the code in "code debug hierarchy " (3D mode), i couldn't see the button there either even though i had added it
Below is my code with an example of label, scrollview and button. It be great if anyone could provide any insights.....thanks either way....
................scrollview..........................
var editInfoView : UIScrollView = {
let view = UIScrollView()
view.translatesAutoresizingMaskIntoConstraints = false
view.contentSize.height = 700
view.backgroundColor = tableBackGroundColor
view.frame = CGRect(x: 0, y: 220, width: 375, height: 400)
return view
}()
.......................label...................
vehicleNumberLabel.translatesAutoresizingMaskIntoConstraints = false
vehicleNumberLabel.textColor = .white
vehicleNumberLabel.text = "Vehicle Number"
vehicleNumberLabel.textAlignment = .left
editInfoView.addSubview(vehicleNumberLabel)
vehicleNumberLabel.leftAnchor.constraint(equalTo: editInfoView.leftAnchor).isActive = true
vehicleNumberLabel.topAnchor.constraint(equalTo: editInfoView.topAnchor, constant: 100).isActive = true
vehicleNumberLabel.widthAnchor.constraint(equalToConstant: 160).isActive = true
vehicleNumberLabel.heightAnchor.constraint(equalToConstant: 20).isActive = true
.....................button................................
vehicleNumberButton.translatesAutoresizingMaskIntoConstraints = false
vehicleNumberButton.setTitleColor(tableTextColor, for: .normal)
vehicleNumberButton.setTitle("Vehicle Number", for: .normal)
vehicleNumberButton.tintColor = tableTextColor
vehicleNumberButton.backgroundColor = tableTextColor
editInfoView.addSubview(vehicleNumberButton)
vehicleNumberButton.rightAnchor.constraint(equalTo: editInfoView.rightAnchor).isActive = true
vehicleNumberButton.topAnchor.constraint(equalTo: editInfoView.topAnchor, constant: 400).isActive = true
vehicleNumberButton.widthAnchor.constraint(equalToConstant: 600).isActive = true
vehicleNumberButton.heightAnchor.constraint(equalToConstant: 255).isActive = true
Although I cannot determine the root cause of your issue with the code and explanation provided I suspect the frame of your UIScrollView() is zero after viewDidAppear(_:) adding subviews to a CGRect.zero can cause some strange behavior with the layout engine. When we create constraints programmatically we are creating a combination of inequalities, equalities, and priorities to restrict the view to a particular frame. If a the value of these constraint equations is incorrect it changes how your relating views appear. Its good practice to avoid the use of leftAnchor and rightAnchor as well, because views may flip direction based on language (writing direction) and user settings.
ViewController.swift
import UIKit
class ViewController: UIViewController {
var editInfoScrollView : UIScrollView = {
let view = UIScrollView()
view.translatesAutoresizingMaskIntoConstraints = false
view.isUserInteractionEnabled = true
view.alwaysBounceVertical = true
view.isScrollEnabled = true
view.contentSize.height = 700
view.backgroundColor = UIColor.red.withAlphaComponent(0.3)
// Does nothing because `translatesAutoresizingMaskIntoConstraints = false`
// Instead, set the content size after activating constraints in viewDidAppear
//view.frame = CGRect(x: 0, y: 220, width: 375, height: 400)
return view
}()
var vehicleNumberLabel: UILabel = {
let label = UILabel()
label.translatesAutoresizingMaskIntoConstraints = false
label.textColor = UIColor.black
label.text = "Vehicle Number"
label.textAlignment = .left
return label
}()
lazy var vehicleNumberButton: UIButton = {
let button = UIButton()
button.translatesAutoresizingMaskIntoConstraints = false
button.tag = 1
button.setTitleColor(UIColor.black, for: .normal)
button.setTitle("Go to Vehicle", for: .normal)
button.tintColor = UIColor.white
button.backgroundColor = UIColor.clear
button.layer.cornerRadius = 30 // about half of button.frame.height
button.layer.borderColor = UIColor.black.cgColor
button.layer.borderWidth = 2.0
button.layer.masksToBounds = true
button.addTarget(self, action: #selector(handelButtons(_:)), for: .touchUpInside)
return button
}()
override func viewDidLoad() {
super.viewDidLoad()
self.view.backgroundColor = UIColor.white
self.setupSubviews()
}
override func viewDidAppear(_ animated: Bool) {
super.viewDidAppear(animated)
self.editInfoScrollView.contentSize = CGSize(width: self.view.frame.width, height: 700.0)
}
func setupSubviews() {
self.view.addSubview(editInfoScrollView)
editInfoScrollView.addSubview(vehicleNumberLabel)
editInfoScrollView.addSubview(vehicleNumberButton)
let spacing: CGFloat = 12.0
let constraints:[NSLayoutConstraint] = [
editInfoScrollView.widthAnchor.constraint(equalTo: self.view.widthAnchor),
editInfoScrollView.heightAnchor.constraint(equalToConstant: 400.0),
editInfoScrollView.centerXAnchor.constraint(equalTo: self.view.centerXAnchor),
editInfoScrollView.centerYAnchor.constraint(equalTo: self.view.centerYAnchor, constant: 220.0),
vehicleNumberLabel.leadingAnchor.constraint(equalTo: editInfoScrollView.leadingAnchor, constant: spacing),
vehicleNumberLabel.trailingAnchor.constraint(equalTo: editInfoScrollView.trailingAnchor, constant: -spacing),
vehicleNumberLabel.centerXAnchor.constraint(equalTo: editInfoScrollView.centerXAnchor, constant: -50),
vehicleNumberLabel.heightAnchor.constraint(equalToConstant: 75.0),
vehicleNumberButton.widthAnchor.constraint(equalTo: editInfoScrollView.widthAnchor, multiplier: 0.66),
vehicleNumberButton.heightAnchor.constraint(equalToConstant: 65.0),
vehicleNumberButton.topAnchor.constraint(equalTo: vehicleNumberLabel.bottomAnchor, constant: spacing),
vehicleNumberButton.centerXAnchor.constraint(equalTo: editInfoScrollView.centerXAnchor),
]
NSLayoutConstraint.activate(constraints)
}
#objc func handelButtons(_ sender: UIButton) {
switch sender.tag {
case 0:
print("Default button tag")
case 1:
print("vehicleNumberButton was tapped")
default:
print("Nothing here yet")
}
}
}

Swift 3 - Constrain Button Width

I am wanting to create a simple bar at the top of my view, with two buttons side by side, taking up 50% each.
I have created the bar like so:
let topTabView = UIView()
topTabView.backgroundColor = UIColor.red
topTabView.translatesAutoresizingMaskIntoConstraints = false
view.addSubview(topTabView)
topTabView.leftAnchor.constraint(equalTo: view.leftAnchor).isActive = true
topTabView.topAnchor.constraint(equalTo: topLayoutGuide.bottomAnchor).isActive = true
topTabView.heightAnchor.constraint(equalToConstant: 60).isActive = true
topTabView.widthAnchor.constraint(equalTo: view.widthAnchor).isActive = true
And this works.
I then add my two buttons, and I get all the constraints right, except I'm not sure how to get the width anchor to work, so that each button takes up 50% of the view.
let filterButton = UIButton()
filterButton.backgroundColor = UIColor.red
filterButton.setTitle("Filter", for: .normal)
filterButton.translatesAutoresizingMaskIntoConstraints = false
topTabView.addSubview(filterButton)
filterButton.leftAnchor.constraint(equalTo: topTabView.leftAnchor).isActive = true
filterButton.centerYAnchor.constraint(equalTo: topTabView.centerYAnchor).isActive = true
filterButton.heightAnchor.constraint(equalTo: topTabView.heightAnchor).isActive = true
// NOT SURE ABOUT THIS ONE
filterButton.widthAnchor.constraint(equalToConstant: 200).isActive = true
let mapButton = UIButton()
mapButton.backgroundColor = UIColor.red
mapButton.setTitle("Map", for: .normal)
mapButton.translatesAutoresizingMaskIntoConstraints = false
topTabView.addSubview(mapButton)
mapButton.rightAnchor.constraint(equalTo: topTabView.rightAnchor).isActive = true
mapButton.centerYAnchor.constraint(equalTo: topTabView.centerYAnchor).isActive = true
mapButton.heightAnchor.constraint(equalTo: topTabView.heightAnchor).isActive = true
// NOT SURE ABOUT THIS ONE
mapButton.widthAnchor.constraint(equalToConstant: 200).isActive = true
I tried something like this but it didn't work:
mapButton.widthAnchor.constraint(equalToConstant: toTabView.frame.width / 2.0).isActive = true
Any help would be amazing!
so that each button takes up 50% of the view
That is what the multiplier is for. You aren't using it. Use it!
So, you want a constraint where a button's width is the same as the superview's width except with a 0.5 value for its multiplier.
Example:
let b1 = UIButton()
b1.translatesAutoresizingMaskIntoConstraints = false
b1.backgroundColor = .green
b1.setTitle("Button1", for: .normal)
b1.setTitleColor(.black, for: .normal)
let b2 = UIButton()
b2.translatesAutoresizingMaskIntoConstraints = false
b2.backgroundColor = .yellow
b2.setTitle("Button2", for: .normal)
b2.setTitleColor(.black, for: .normal)
self.view.addSubview(b1)
self.view.addSubview(b2)
NSLayoutConstraint.activate([
b1.topAnchor.constraint(equalTo: self.view.topAnchor, constant: 50),
b2.topAnchor.constraint(equalTo: self.view.topAnchor, constant: 50),
b1.leadingAnchor.constraint(equalTo:self.view.leadingAnchor),
b2.leadingAnchor.constraint(equalTo:b1.trailingAnchor),
b1.widthAnchor.constraint(equalTo: self.view.widthAnchor, multiplier: 0.5),
b2.widthAnchor.constraint(equalTo: self.view.widthAnchor, multiplier: 0.5),
])
Result: