WKWebViewController with secure progress observation, progressView and activityIndicatorView

ProgressObservableWebViewController.swift

import UIKit
import WebKit

open class ProgressObservableWebViewController: UIViewController, WKWebViewProgressObservable {
    @IBOutlet weak public var webView: WKWebView!
    
    public var webViewProgressObservation: Any?
        
    private let progressView: UIProgressView = {
        let view = UIProgressView(progressViewStyle: .default)
        view.progressTintColor = .blue
        view.translatesAutoresizingMaskIntoConstraints = false
        return view
    }()
    
    private let activityIndicatorView: UIActivityIndicatorView = {
        let activityView = UIActivityIndicatorView(style: .gray)
        activityView.startAnimating()
        activityView.translatesAutoresizingMaskIntoConstraints = false
        activityView.hidesWhenStopped = true
        return activityView
    }()
    
    override open func viewDidLoad() {
        super.viewDidLoad()
        
        setupUI()
        
        startWebViewProgressObservation { [weak self] value in
            self?.progressView.progress = Float(value)
        }
    }
    
    public func showLoading() {
        activityIndicatorView.startAnimating()
        UIView.animate(withDuration: 0.5, delay: 0, options: .curveEaseInOut, animations: {
            self.progressView.alpha = 1
        }, completion: nil)
    }
    
    public func hideLoading() {
        activityIndicatorView.stopAnimating()
        UIView.animate(withDuration: 0.5, delay: 0.5, options: .curveEaseInOut, animations: {
            self.progressView.alpha = 0
        }, completion: nil)
    }
}

private extension ProgressObservableWebViewController {
    func setupUI() {
        [progressView].forEach { self.view.addSubview($0) }
        progressView.leadingAnchor.constraint(equalTo: webView.leadingAnchor).isActive = true
        progressView.trailingAnchor.constraint(equalTo: webView.trailingAnchor).isActive = true
        progressView.topAnchor.constraint(equalTo: webView.safeAreaLayoutGuide.topAnchor).isActive = true
        progressView.heightAnchor.constraint(equalToConstant: 4).isActive = true
        
        webView.embed(activityIndicatorView)
        activityIndicatorView.centerXAnchor.constraint(equalTo: webView.centerXAnchor).isActive = true
        activityIndicatorView.centerYAnchor.constraint(equalTo: webView.centerYAnchor).isActive = true
    }
}

public protocol WKWebViewProgressObservable: AnyObject {
    var webView: WKWebView! { get set }
    var webViewProgressObservation: Any? { get set }
    typealias WebViewProgressObservableCompletionHandler = (_ value: Double) -> Void
    func startWebViewProgressObservation(completion: WebViewProgressObservableCompletionHandler?)
    func stopWebViewProgressObservation()
}

public extension WKWebViewProgressObservable {
    func startWebViewProgressObservation(completion: WebViewProgressObservableCompletionHandler?) {
        webViewProgressObservation = webView.observe(\.estimatedProgress) { (webView, _) in
            completion?(webView.estimatedProgress)
        }
    }
    
    func stopWebViewProgressObservation() {
        webViewProgressObservation = nil
    }
}

public extension UIView {
    func embed(_ view: UIView) {
        view.translatesAutoresizingMaskIntoConstraints = false
        addSubview(view)
        view.leftAnchor.constraint(equalTo: leftAnchor).isActive = true
        view.rightAnchor.constraint(equalTo: rightAnchor).isActive = true
        view.topAnchor.constraint(equalTo: topAnchor).isActive = true
        view.bottomAnchor.constraint(equalTo: bottomAnchor).isActive = true
    }
}