Create UIButtons with dynamic font size but all share same font size in UIStackView - swift

Question

I am using UIStackView and adding three buttons to it. I want it so that the button with the most text (B1) will be auto resized to fit the width and the other buttons will share the same font size as B1.
#IBOutlet weak var stackView: UIStackView!
var btnTitles = [String]()
btnTitles.append("Practice Exams")
btnTitles.append("Test Taking Tips")
btnTitles.append("About")
createButtons(buttonTitles: btnTitles)
var min = CGFloat(Int.max) // keep track of min font
func createButtons(buttonTitles: [String]) {
var Buttons = [UIButton]()
for title in buttonTitles {
let button = makeButtonWithText(text: title)
// set the font to dynamically size
button.titleLabel!.numberOfLines = 1
button.titleLabel!.adjustsFontSizeToFitWidth = true
button.titleLabel!.baselineAdjustment = .alignCenters // I think it keeps it centered vertically
button.contentEdgeInsets = UIEdgeInsetsMake(5, 10, 5, 10); // set margins
if (button.titleLabel?.font.pointSize)! < min {
min = (button.titleLabel?.font.pointSize)! // to get the minimum font size of any of the buttons
}
stackView.addArrangedSubview(button)
Buttons.append(button)
}
}
func makeButtonWithText(text:String) -> UIButton {
var myButton = UIButton(type: UIButtonType.system)
//Set a frame for the button. Ignored in AutoLayout/ Stack Views
myButton.frame = CGRect(x: 30, y: 30, width: 150, height: 100)
// background color - light blue
myButton.backgroundColor = UIColor(red: 0.255, green: 0.561, blue: 0.847, alpha: 1)
//State dependent properties title and title color
myButton.setTitle(text, for: UIControlState.normal)
myButton.setTitleColor(UIColor.white, for: UIControlState.normal)
// set the font to dynamically size
myButton.titleLabel!.font = myButton.titleLabel!.font.withSize(70)
myButton.contentHorizontalAlignment = .center // align center
return myButton
}
I wanted to find the minimum font size and then set all the buttons to the minimum in viewDidAppear button the font prints as 70 for all of them even though they clearly appear different sizes (see image)
override func viewDidAppear(_ animated: Bool) {
print("viewDidAppear")
let button = stackView.arrangedSubviews[0] as! UIButton
print(button.titleLabel?.font.pointSize)
let button1 = stackView.arrangedSubviews[1] as! UIButton
print(button1.titleLabel?.font.pointSize)
let button2 = stackView.arrangedSubviews[2] as! UIButton
print(button2.titleLabel?.font.pointSize)
}
image

Answer 1

You can try playing around with this func to return the scaled-font-size of a label:
func actualFontSize(for aLabel: UILabel) -> CGFloat {
// label must have text, must have .minimumScaleFactor and must have .adjustsFontSizeToFitWidth == true
guard let str = aLabel.text,
aLabel.minimumScaleFactor > 0.0,
aLabel.adjustsFontSizeToFitWidth
else { return aLabel.font.pointSize }
let attributes = [NSAttributedString.Key.font : aLabel.font]
let attStr = NSMutableAttributedString(string:str, attributes:attributes as [NSAttributedString.Key : Any])
let context = NSStringDrawingContext()
context.minimumScaleFactor = aLabel.minimumScaleFactor
_ = attStr.boundingRect(with: aLabel.bounds.size, options: .usesLineFragmentOrigin, context: context)
return aLabel.font.pointSize * context.actualScaleFactor
}
On viewDidAppear() you would loop through the buttons, getting the smallest actual font size, then set the font size for each button to that value.
It will take some experimentation... For one thing, I've noticed in the past that font-sizes can get rounded - so setting a label's font point size to 20.123456789 won't necessarily give you that exact point size. Also, since this changes the actual font size assigned to the labels, you'll need to do some resetting if you change the button title dynamically. Probably also need to account for button frame changes (such as with device rotation, etc).
But... here is a quick test that you can run to see the approach:
class TestViewController: UIViewController {
let stackView: UIStackView = {
let v = UIStackView()
v.translatesAutoresizingMaskIntoConstraints = false
v.axis = .vertical
v.alignment = .center
v.distribution = .fillEqually
v.spacing = 8
return v
}()
var btnTitles = [String]()
var theButtons = [UIButton]()
override func viewDidLoad() {
super.viewDidLoad()
setupUI()
}
override func viewDidAppear(_ animated: Bool) {
super.viewDidAppear(animated)
fixButtonFonts()
}
func setupUI() -> Void {
view.addSubview(stackView)
NSLayoutConstraint.activate([
stackView.topAnchor.constraint(equalTo: view.safeAreaLayoutGuide.topAnchor, constant: 40),
stackView.leadingAnchor.constraint(equalTo: view.safeAreaLayoutGuide.leadingAnchor, constant: 40),
stackView.trailingAnchor.constraint(equalTo: view.safeAreaLayoutGuide.trailingAnchor, constant: -40),
])
btnTitles.append("Practice Exams")
btnTitles.append("Test Taking Tips")
btnTitles.append("About")
createButtons(buttonTitles: btnTitles)
}
func fixButtonFonts() -> Void {
var minActual = CGFloat(70)
// get the smallest actual font size
theButtons.forEach { btn in
if let lbl = btn.titleLabel {
let act = actualFontSize(for: lbl)
// for debugging
//print("actual font size: \(act)")
minActual = Swift.min(minActual, act)
}
}
// set font size for each button
theButtons.forEach { btn in
if let lbl = btn.titleLabel {
lbl.font = lbl.font.withSize(minActual)
}
}
}
func createButtons(buttonTitles: [String]) {
for title in buttonTitles {
let button = makeButtonWithText(text: title)
// set the font to dynamically size
button.titleLabel!.numberOfLines = 1
button.titleLabel!.adjustsFontSizeToFitWidth = true
// .minimumScaleFactor is required
button.titleLabel!.minimumScaleFactor = 0.05
button.titleLabel!.baselineAdjustment = .alignCenters // I think it keeps it centered vertically
button.contentEdgeInsets = UIEdgeInsets(top: 5, left: 10, bottom: 5, right: 10); // set margins
stackView.addArrangedSubview(button)
theButtons.append(button)
}
}
func makeButtonWithText(text:String) -> UIButton {
let myButton = UIButton(type: UIButton.ButtonType.system)
//Set a frame for the button. Ignored in AutoLayout/ Stack Views
myButton.frame = CGRect(x: 30, y: 30, width: 150, height: 100)
// background color - light blue
myButton.backgroundColor = UIColor(red: 0.255, green: 0.561, blue: 0.847, alpha: 1)
//State dependent properties title and title color
myButton.setTitle(text, for: UIControl.State.normal)
myButton.setTitleColor(UIColor.white, for: UIControl.State.normal)
// set the font to dynamically size
myButton.titleLabel!.font = myButton.titleLabel!.font.withSize(70)
myButton.contentHorizontalAlignment = .center // align center
return myButton
}
func actualFontSize(for aLabel: UILabel) -> CGFloat {
// label must have text, must have .minimumScaleFactor and must have .adjustsFontSizeToFitWidth == true
guard let str = aLabel.text,
aLabel.minimumScaleFactor > 0.0,
aLabel.adjustsFontSizeToFitWidth
else { return aLabel.font.pointSize }
let attributes = [NSAttributedString.Key.font : aLabel.font]
let attStr = NSMutableAttributedString(string:str, attributes:attributes as [NSAttributedString.Key : Any])
let context = NSStringDrawingContext()
context.minimumScaleFactor = aLabel.minimumScaleFactor
_ = attStr.boundingRect(with: aLabel.bounds.size, options: .usesLineFragmentOrigin, context: context)
return aLabel.font.pointSize * context.actualScaleFactor
}
}
Result: