UIStackView, arrange subviews only while they fit - ios

Question

I have an array of UIButtons that I am trying to add to an horizontal UIStackView. The number of these buttons is dynamic and they can become that high to not fit on the screen.
For my use case I would like to add the buttons, from the left of my stack view, while they fit on the screen. So if I have 10 buttons, and after adding the 5th one there would not be enough space to add the 6th button, I would like to stop at that moment.
Does anybody knows a good approach to get this behaviour?
My current code looks similar to this:
import UIKit
class ViewController: UIViewController {
let items = ["One", "Two", "Three", "Four", "Five", "Six", "Seven", "Eight", "Nine", "Ten", "Eleven"]
override func viewDidLoad() {
super.viewDidLoad()
let stackView = UIStackView()
stackView.axis = .horizontal
stackView.spacing = 5
view.addSubview(stackView)
for title in items {
let button = UIButton()
button.backgroundColor = .red
button.setTitle(title, for: .normal)
// if button.doesNotFit() {
// break
// }
stackView.addArrangedSubview(button)
}
let spacerView = UIView()
spacerView.setContentHuggingPriority(.defaultLow, for: .horizontal)
stackView.addArrangedSubview(spacerView)
stackView.translatesAutoresizingMaskIntoConstraints = false
stackView.leadingAnchor.constraint(equalTo: view.leadingAnchor).isActive = true
stackView.trailingAnchor.constraint(equalTo: view.trailingAnchor).isActive = true
stackView.centerYAnchor.constraint(equalTo: view.centerYAnchor).isActive = true
stackView.heightAnchor.constraint(equalToConstant: 50).isActive = true
}
}
With that, i get the following result. The problem is in the button "Nine", "Ten", etc... because they do not fit. I would not like them to be added to the UIStackView.

Answer 1

What you'll need to do...
in viewDidLoad()
create the buttons and add them to an array
in viewDidLayoutSubviews() (so we have a valid width of the view)
get the available width
clear any existing buttons from the stack view
loop through the buttons array, adding the width of the button + spacing
if the width is less than available width, add the button to the stack view
Here is a full example. I included .left, .right and .justified options:
// ButtonsAlignment is
// left = buttons will be left-aligned with fixed spacing
// right = buttons will be right-aligned with fixed spacing
// justified = buttons will be justified edge to edge with equal spacing
enum ButtonsAlignment {
case left
case right
case justified
}
class StackSpacingViewController: UIViewController {
let items = ["One", "Two", "Three", "Four", "Five", "Six", "Seven", "Eight", "Nine", "Ten", "Eleven"]
// array to hold your buttons
var buttonsArray: [UIButton] = []
// change to .left, .right, .justified to see the difference
let spacingMode: ButtonsAlignment = .left
// if mode is .justified, this will be the minimum spacing
let buttonSpacing: CGFloat = 5.0
// need to track when the view width changes (when auto-layout has set it)
// for use in viewDidLayoutSubviews()
var viewWidth: CGFloat = 0.0
// we'll need to refrence the stack view in multiple places,
// so don't make it local to viewDidLoad()
let stackView = UIStackView()
override func viewDidLoad() {
super.viewDidLoad()
stackView.axis = .horizontal
if spacingMode == .left || spacingMode == .right {
stackView.distribution = .fill
stackView.spacing = buttonSpacing
} else {
stackView.distribution = .equalSpacing
}
view.addSubview(stackView)
for title in items {
let button = UIButton()
button.backgroundColor = .red
button.setTitle(title, for: .normal)
// append it to the buttonsArray
buttonsArray.append(button)
}
stackView.translatesAutoresizingMaskIntoConstraints = false
stackView.centerYAnchor.constraint(equalTo: view.centerYAnchor).isActive = true
stackView.heightAnchor.constraint(equalToConstant: 50).isActive = true
if spacingMode == .left || spacingMode == .justified {
stackView.leadingAnchor.constraint(equalTo: view.leadingAnchor).isActive = true
}
if spacingMode == .right || spacingMode == .justified {
stackView.trailingAnchor.constraint(equalTo: view.trailingAnchor).isActive = true
}
}
override func viewDidLayoutSubviews() {
super.viewDidLayoutSubviews()
// this can (likely will) be called multiple times
// so only update the buttons stack view when the
// view's width changes
if viewWidth != view.frame.width {
let w = view.frame.width
viewWidth = w
// clear any buttons already in the stack
stackView.subviews.forEach {
$0.removeFromSuperview()
}
var curWidth: CGFloat = 0.0
for btn in buttonsArray {
curWidth += btn.intrinsicContentSize.width + buttonSpacing
if curWidth < w {
stackView.addArrangedSubview(btn)
}
}
stackView.setNeedsLayout()
stackView.layoutIfNeeded()
}
}
}
Note: this could (probably would) work better as a self-contained custom view class... would make it easy to add a "background" color, and the calculations could be handled in the subclass's layoutSubviews() function.