Constraints appear to change UIButton frame size

Question

Background

I’m trying to create a UIButton with a 300px width and 200px height.

Then, I’m trying to position that UIButton centred horizontally and 50 pixels from the bottom.

When running the code in the iOS simulator, the result is unexpected, the button height and width is not correct, the UIButton appears cropped. Image below.

Question

What corrections to the code below must be made so that the UIButton layout is positioned correctly and retains the correct sized UIButton frame?

Code

import UIKit

class ViewController: UIViewController {

    override func viewDidLoad() {
        super.viewDidLoad()
        
        addButton1()
    }

    func addButton1() {
        let myButton1 = UIButton(type: UIButton.ButtonType.custom)
        myButton1.frame.size = CGSize(width: 300, height: 200)
        myButton1.setTitle("Hello", for:UIControl.State())
        myButton1.backgroundColor =  .blue
        view.addSubview(myButton1)
        myButton1.translatesAutoresizingMaskIntoConstraints = false
        NSLayoutConstraint.activate([
            myButton1.centerXAnchor.constraint(equalTo: view.centerXAnchor),
            myButton1.bottomAnchor.constraint(equalTo: view.bottomAnchor, constant: -50)
        ])
    }

}

Image

Fabio Felici · Accepted Answer · 2021-08-04 08:39:17Z

2

You are mixing legacy frame approach with AutoLayout and that would not work. I suggest to stick with AutoLayout and so your code could be:

class ViewController: UIViewController {

  override func viewDidLoad() {
    super.viewDidLoad()

    addButton1()
  }

  func addButton1() {
    let myButton1 = UIButton(type: UIButton.ButtonType.custom)
    myButton1.setTitle("Hello", for:UIControl.State())
    myButton1.backgroundColor =  .blue
    view.addSubview(myButton1)
    myButton1.translatesAutoresizingMaskIntoConstraints = false
    NSLayoutConstraint.activate([
      myButton1.widthAnchor.constraint(equalToConstant: 300),
      myButton1.heightAnchor.constraint(equalToConstant: 200),
      myButton1.centerXAnchor.constraint(equalTo: view.centerXAnchor),
      myButton1.bottomAnchor.constraint(equalTo: view.bottomAnchor, constant: -50)
    ])
  }

}

answered Aug 4, 2021 at 8:39

Fabio Felici

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1 Comment

user4806509 Over a year ago

Perfect. Thank you very much for explaining the issue.

Hailey · Accepted Answer · 2021-08-04 08:41:35Z

You can give the height and width of the button through NSLayoutConstraint.

func addButton1() {
        let myButton1 = UIButton(type: UIButton.ButtonType.custom)
        myButton1.setTitle("Hello", for:UIControl.State())
        myButton1.backgroundColor =  .blue
        view.addSubview(myButton1)
        myButton1.translatesAutoresizingMaskIntoConstraints = false
        myButton1.widthAnchor.constraint(equalToConstant: 300).isActive = true
        myButton1.heightAnchor.constraint(equalToConstant: 200).isActive = true
        myButton1.centerXAnchor.constraint(equalTo: view.centerXAnchor).isActive = true
        myButton1.bottomAnchor.constraint(equalTo: view.bottomAnchor, constant: -50).isActive = true
    }

Cuong Nguyen · Accepted Answer · 2021-08-04 08:46:19Z

1

As my knowledge, I think we could try with Aspect ratio.

For example:

button.heightAnchor.constraint(equalTo: button.widthAnchor, multiplier: 1.0/4.0).isActive = true

button.translatesAutoresizingMaskIntoConstraints = false
let margins = view.layoutMarginsGuide
button.leadingAnchor.constraint(equalTo: margins.leadingAnchor, constant: 16.0).isActive = true
button.trailingAnchor.constraint(equalTo: margins.trailingAnchor, constant: -16.0).isActive = true
button.bottomAnchor.constraint(equalTo: margins.bottomAnchor, constant: -20.0).isActive = true
button.heightAnchor.constraint(equalTo: button.widthAnchor, multiplier: 1.0/4.0).isActive = true

If you have a time please reading carefully a apple document for autolayout

answered Aug 4, 2021 at 8:46

Cuong Nguyen

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2 Comments

user4806509 Over a year ago

The heightAnchor didn't display as expected as the multiplier needed to be 200/300. After changing that it worked. Interesting approach. Thank you.

Cuong Nguyen Over a year ago

Yeah! Happy to hear that. Actually, in case I think we should use aspect ratio because it helps the button fit with all iphone version.

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