Accessing html response content in Xamarin browser control

Question

I have what seems to be an unusual requirement that my colleagues and I haven\'t been able to implement in our Xamarin project. What we are trying to do is dynamically proce

Answer 1

Both these device-dependent techniques use JavaScript evaluation/execution after the HTML page has finished loading in order for to receive the entire html contents as a JavaScript result (edit the JavaScript in the examples if your requirements to not require the entire page to be return).

Xamarin.Android

You can capture the loaded html within a WebView by assigning a subclassed WebViewClient that implements IValueCallback. The OnReceiveValue method will contain the html content after the page has finished loading:

Example WebViewClient Class:

public class EmbeddedWebViewClient : WebViewClient, IValueCallback
{
    public EmbeddedWebViewClient(WebView view)
    {
        view.Settings.JavaScriptEnabled = true;
    }

    public override void OnPageFinished(WebView view, string url)
    {
        base.OnPageFinished(view, url);
        Log.Info("SO", $"Page loaded from: {url}");
        view.EvaluateJavascript("(function() { return (''+document.getElementsByTagName('html')[0].innerHTML+''); })();", this);
    }

    public void OnReceiveValue(Java.Lang.Object value)
    {
        // "value" holds the html contents of the loaded page
        Log.Debug("SO", ((string)value).Substring(0, 40));
    }
}

Example WebViewClient usage:

WebView webview = FindViewById(Resource.Id.webview);
webview.SetWebViewClient(new EmbeddedWebViewClient(webview));
webview.LoadUrl("https://xamarin.com");

Xamarin.iOS

You can capture the loaded html within a WKWebView by assigning a IWKNavigationDelegate to it. Either implement it within its own class or the controller that contains the WKWebView

Example IWKNavigationDelegate Implementation:

public class NavigationDelegate : NSObject, IWKNavigationDelegate
{
    [Export("webView:didFinishNavigation:")]
    public async void DidFinishNavigation(WKWebView webView, WKNavigation navigation)
    {
        var content = await webView.EvaluateJavaScriptAsync("(function() { return (''+document.getElementsByTagName('html')[0].innerHTML+''); })();");
        var html = FromObject(content);
        Console.WriteLine((html.ToString()).Substring(0, 40));
    }
}

Example WKWebView usage:

wkwebview = new WKWebView(UIScreen.MainScreen.Bounds, new WKWebViewConfiguration());
wkwebview.NavigationDelegate = new NavigationDelegate();
Add(wkwebview);
wkwebview.LoadRequest(new NSUrlRequest(new Uri("https://xamarin.com")));

Note: This same basic logic can be done with a UIWebView, but WKWebView is so much faster that if you do not need to support iOS 7 clients, I would personally focus on using WKWebView