Making a UIButton a % of the screen size

Question

I noticed certain button sizes look great on one the iPhone 5 simulator but do not look as good on the iPhone 6 simulator and this is because the heights or constraints that

Answer 1

This function gives you the bounds of the screen

var bounds = UIScreen.mainScreen().bounds

And then you can set the button width multipliying 0.4 x bounds.size.width

Regards

Answer 2

Swift 4.2

In code it's really easy:

override func viewDidLoad() {
        super.viewDidLoad()

        view.addSubview(button)
        button.centerXAnchor.constraint(equalTo: view.centerXAnchor).isActive = true
        button.centerYAnchor.constraint(equalTo: view.centerYAnchor).isActive = true

        button.widthAnchor.constraint(equalToConstant: 100).isActive = true
        button.heightAnchor.constraint(equalToConstant: UIScreen.main.bounds.height * 0.4).isActive = true
    }

or use this instead of current heightAnchor:

button.heightAnchor.constraint(equalTo: view.heightAnchor, multiplier: 0.4).isActive = true

hope this help :)

Answer 3

1. Ctrl drag from button to superview and select Equal Widths

2. Open Size Inspector edit Equal Widths constraint and set multiplier to 0.4. And you will see something like this:

3. Add missing constraints and update frames.

Answer 4

You can't set a constraint to be 40% of the screen height. However, if the button always has a 20px leading and trailing to the superview you could use that width and set an aspect ratio height.

Another way could be to use UIScreen.mainScreen().bounds.size.height * 0.4 for your button height.

A third way is to use the button's superview to set the height. Assuming that your button is a direct child of a UIViewController's view: view.bounds.size.height * 0.4.

There's probably a bunch of other ways to do this as well but none of them will involve setting the height to an actual percentage as far as I'm aware.