How can I tell if an iPhone's home indicator is present or not in xcode?

Question

I have placed a button at the bottom of the safe area.

On iPhone X and later devices, it is placed well above a certain margin, but in the case of an iPhone with a home button, it is attached to the bottom.

So, I would like to set a separate constraint only on iPhones with a home button to leave a certain margin.

iPhoneSE

iPhone 13 Pro

Answer 1

You don't need to detect the home button... in fact, that's probably not what you want to do anyway.

Another approach is to use two bottom constraints, with different priorities.

You can constrain the bottom of the button to the bottom of the safe area, and give that constraint a less-than-required priority.

You can then apply another constraint, this time at a minimum distance from the bottom of the view.

Here's an example:

class BottomPaddingViewController: UIViewController {

    override func viewDidLoad() {
        super.viewDidLoad()
        
        let safeAreaView = UIView()
        safeAreaView.backgroundColor = .red
        safeAreaView.translatesAutoresizingMaskIntoConstraints = false
        view.addSubview(safeAreaView)
        
        let btn = UIButton()
        btn.backgroundColor = .systemBlue
        btn.setTitle("Button", for: [])
        btn.translatesAutoresizingMaskIntoConstraints = false
        view.addSubview(btn)
        
        let g = view.safeAreaLayoutGuide
        
        // bottom constraint for the button
        //  to the safe area bottom
        //  with less-than-required priority
        let bConstraint = btn.bottomAnchor.constraint(equalTo: g.bottomAnchor)
        bConstraint.priority = .required - 1
        
        NSLayoutConstraint.activate([
            
            // constrain the red view to the safe area bottom
            safeAreaView.bottomAnchor.constraint(equalTo: g.bottomAnchor),
            safeAreaView.leadingAnchor.constraint(equalTo: g.leadingAnchor),
            safeAreaView.trailingAnchor.constraint(equalTo: g.trailingAnchor),
            safeAreaView.heightAnchor.constraint(equalToConstant: 40.0),
            
            // constrain button 200-pts wide, centered horizontally
            btn.widthAnchor.constraint(equalToConstant: 200.0),
            btn.heightAnchor.constraint(equalToConstant: 40.0),
            btn.centerXAnchor.constraint(equalTo: g.centerXAnchor),

            // and bottom AT LEAST 20-points from the bottom of the VIEW
            btn.bottomAnchor.constraint(lessThanOrEqualTo: view.bottomAnchor, constant: -20.0),
            
            // activate the button's safe area bottom constraint
            bConstraint,
        ])
    }
    
}

When running on a phone without a physical button (iPhone 12, for example) it looks like this:

we see that both the blue button and the red view are bottom-constrained to the safe area.

When running on a phone with a physical button (iPhone 8, for example) it looks like this:

the red view is still constrained to the safe area, but the blue button keeps its minimum distance from the view bottom.