How to add Activity Indicator to WKWebView (Swift 3)

I have a wkwebview in my app, and I want to add an activity indicator to it. I want it to where it appears when the webview is loading and disappears whenever it is finished loading, it disappears. Can you give me some code to do this? Here's my code right now:

@IBOutlet weak var Activity: UIActivityIndicatorView!
var webView : WKWebView!


@IBOutlet var containerView: UIView? = nil


override func viewDidLoad() {
    super.viewDidLoad()

    guard let url = URL(string: "http://ifunnyvlogger.wixsite.com/ifunnyvlogger/app-twitter") else { return }

    webView = WKWebView(frame: self.view.frame)
    webView.translatesAutoresizingMaskIntoConstraints = false
    webView.isUserInteractionEnabled = true
    webView.navigationDelegate = self

    self.view.addSubview(self.webView)

    let request = URLRequest(url: url)
    webView.load(request)

}


func webView(_ webView: WKWebView, decidePolicyFor navigationAction: WKNavigationAction, decisionHandler: @escaping (WKNavigationActionPolicy) -> Void) {

    // Check if a link was clicked
    if navigationAction.navigationType == .linkActivated {

        // Verify the url
        guard let url = navigationAction.request.url else { return }
        let shared = UIApplication.shared

        // Check if opening in Safari is allowd
        if shared.canOpenURL(url) {

            // Ask the user if they would like to open link in Safari
            let alert = UIAlertController(title: "Do you want to open Safari?", message: nil, preferredStyle: .alert)
            alert.addAction(UIAlertAction(title: "Yes", style: .default, handler: { (alert: UIAlertAction) -> Void in
                // User wants to open in Safari
                shared.open(url, options: [:], completionHandler: nil)
            }))
            alert.addAction(UIAlertAction(title: "Opps, no.", style: .cancel, handler: nil))

            present(alert, animated: true, completion: nil)

        }
        decisionHandler(.cancel)
    }
    decisionHandler(.allow)
}

func webViewDidStartLoad(_ : WKWebView) {
    Activity.startAnimating()
}

func webViewDidFinishLoad(_ : WKWebView) {
    Activity.startAnimating()
}

I'm creating an IOS app using xcode 8 and swift 3

Please, below code which is working fine.

@IBOutlet weak var Activity: UIActivityIndicatorView!
var webView : WKWebView!
@IBOutlet var containerView: UIView? = nil

override func viewDidLoad() {
    super.viewDidLoad()
    
    guard let url = URL(string: "http://www.facebook.com") else { return }
    webView = WKWebView(frame: self.view.frame)
    webView.translatesAutoresizingMaskIntoConstraints = false
    webView.isUserInteractionEnabled = true
    self.view.addSubview(self.webView)
    let request = URLRequest(url: url)
    webView.load(request)
    
    // add activity
    self.webView.addSubview(self.Activity)
    self.Activity.startAnimating()
    self.webView.navigationDelegate = self
    self.Activity.hidesWhenStopped = true
    
}

Implement below these two delegate method:

func webView(_ webView: WKWebView, didFinish navigation: WKNavigation!) {
    Activity.stopAnimating()
}

func webView(_ webView: WKWebView, didFail navigation: WKNavigation!, withError error: Error) {
    Activity.stopAnimating()
}

Let me know if it is not working.