title: How to add Activity Indicator to WKWebView (Swift 3)
body: <p>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:</p>
  
  <pre><code>@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) -&gt; 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) -&gt; 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()
  }
  </code></pre>
  
  <p>I'm creating an IOS app using xcode 8 and swift 3</p>