A button with activity indicator in the center.

IndicatorViewButton.swift

import UIKit

class IndicatorViewButton: UIButton {

    var roundedCornerRequired: Bool = true
    
    private var indicatorView: UIActivityIndicatorView = {
        let aiv = UIActivityIndicatorView(activityIndicatorStyle: UIActivityIndicatorViewStyle.white)
        aiv.hidesWhenStopped = true
        aiv.translatesAutoresizingMaskIntoConstraints = false
        aiv.isUserInteractionEnabled = false
        return aiv
    }()
    
    var isAnimating: Bool {
        return indicatorView.isAnimating
    }
    
    private var previousText: String?
    
    override init(frame: CGRect) {
        super.init(frame: frame)
        setup()
    }
    
    required init?(coder aDecoder: NSCoder) {
        super.init(coder: aDecoder)
        setup()
    }
    
    func setup() {
        self.previousText = currentTitle
        self.addSubview(indicatorView)
        indicatorView.centerXAnchor.constraint(equalTo: self.centerXAnchor).isActive = true
        indicatorView.centerYAnchor.constraint(equalTo: self.centerYAnchor).isActive = true
    }
    
    override func layoutSubviews() {
        super.layoutSubviews()
        if roundedCornerRequired {
            self.layer.cornerRadius = self.frame.height / 2
        }
        self.setTitleColor(.white, for: .normal)
        self.setTitle(previousText, for: .normal)
    }
    
    override func setTitle(_ title: String?, for state: UIControlState) {
        guard !isAnimating else { return }
        super.setTitle(title, for: state)
        self.previousText = title
    }
    
    func startAnimating() {
        self.setTitle("", for: .normal)
        indicatorView.startAnimating()
    }
    
    func stopAnimating() {
        self.setTitle(previousText, for: .normal)
        self.setTitleColor(.white, for: .normal)
        self.indicatorView.stopAnimating()
    }

}