How to use UIActivityIndicatorView to show a spinner when work is happening

Swift version: 5.6

Paul Hudson @twostraws May 28th 2019

If you need a simple visual way to show users that some activity is happening, UIActivityIndicatorView is the easiest approach. In fact, if you create a dedicated activity indicator view controller, you can cause the whole screen to dim without much code.

To try it out, create a new Cocoa Touch Class called SpinnerViewController, then give it this code:

import UIKit

class SpinnerViewController: UIViewController {
    var spinner = UIActivityIndicatorView(style: .whiteLarge)

    override func loadView() {
        view = UIView()
        view.backgroundColor = UIColor(white: 0, alpha: 0.7)

        spinner.translatesAutoresizingMaskIntoConstraints = false
        spinner.startAnimating()
        view.addSubview(spinner)

        spinner.centerXAnchor.constraint(equalTo: view.centerXAnchor).isActive = true
        spinner.centerYAnchor.constraint(equalTo: view.centerYAnchor).isActive = true
    }
}

You can now use view controller containment to embed that inside your current view controller so that it disables your controls. Something like this ought to be enough to get you started:

func createSpinnerView() {
    let child = SpinnerViewController()

    // add the spinner view controller
    addChild(child)
    child.view.frame = view.frame
    view.addSubview(child.view)
    child.didMove(toParent: self)

    // wait two seconds to simulate some work happening
    DispatchQueue.main.asyncAfter(deadline: .now() + 2) {
        // then remove the spinner view controller
        child.willMove(toParent: nil)
        child.view.removeFromSuperview()
        child.removeFromParent()
    }
}