decisionHandler(WKNavigationActionPolicyAllow, WKWebpagePreferences

  func webView(_ webView: WKWebView, didStartProvisionalNavigation navigation: WKNavigation) {
        UIApplication.shared.isNetworkActivityIndicatorVisible = true
        print("didStartProvisionalNavigation: \(navigation)")
    }

func webView(_ webView: WKWebView, didReceiveServerRedirectForProvisionalNavigation navigation: WKNavigation) {
        print("didReceiveServerRedirectForProvisionalNavigation: \(navigation)")
    }

    func webView(_ webView: WKWebView, didFailProvisionalNavigation navigation: WKNavigation, withError error: Error) {
        print("didFailProvisionalNavigation: \(navigation), error: \(error)")
    }

func webView(_ webView: WKWebView, didFinishLoading navigation: WKNavigation) {
        UIApplication.shared.isNetworkActivityIndicatorVisible = false
        print("didFinishLoadingNavigation: \(navigation)")
    }


    func _webViewWebProcessDidCrash(_ webView: WKWebView) {
        print("WebContent process crashed; reloading")
    }

func webView(_ webView: WKWebView,createWebViewWith configuration: WKWebViewConfiguration, for navigationAction: WKNavigationAction, windowFeatures: WKWindowFeatures) -> WKWebView?{
        //if <a> tag does not contain attribute or has _blank then navigationAction.targetFrame will return nil
        if let trgFrm = navigationAction.targetFrame {

            if(!trgFrm.isMainFrame){
                UIApplication.shared.isNetworkActivityIndicatorVisible = true
                self.webView.load(navigationAction.request)
            }
        }



    return nil
}

func webView(_ webView: WKWebView, didFinish navigation: WKNavigation!){

    UIApplication.shared.isNetworkActivityIndicatorVisible = false
    print("didFinish: \(String(describing: self.webView.url)); stillLoading:\(self.webView.isLoading ? "NO" : "YES")")

}



func webView(_ webView: WKWebView, decidePolicyFor navigationResponse: WKNavigationResponse, decisionHandler: @escaping (_: WKNavigationResponsePolicy) -> Void) {
    print("decidePolicyForNavigationResponse")
    decisionHandler(.allow)
}

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

     decisionHandler(.allow)
}