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 I place on the UIButtons end up leaving a lot of blank space down the bottom of my App Screen.

I would like to have a button that is 40% of the screen size regardless of what device I am simulating on.

Any ideas on how to make the size of the button stay 40% of the screen size regardless of the device?

Answer 1

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 2

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.