What is the easiest way to call c# method from javascript in UIWebview iOS?

Question

I am working on developing iOS application using Xamarin. I have a requirement to call c# method from JavaScript inside UIWebView. How could we achieve that?

The following is html content is loading into UIWebView

const string html = @"
                    <html>
                      <body onload=""setBarcodeInTextField()"">
                        <p>Demo calling C# from JavaScript</p>
                        <button type=""button"" 
                                onClick=""CSharp.ScanBarcode('txtBarcode', 'setBarcodeInTextField')"">Scan Barcode
                        </button>
                        <input type=""text"" value="""" id=""txtBarcode""/>

                        <script type=""text/javascript"">



                        function setBarcodeInTextField() {

                            alert(""JS"");
                        }

                        </script>

                      </body>
                    </html>";

Also, i am getting about://(null) in alert message (onload specified on body tag for displaying alert) when UIWebView loads the html content.

did you have any luck with this?

Michał Żołnieruk
– Michał Żołnieruk

2018-04-10 06:49:22 +00:00
Commented Apr 10, 2018 at 6:49 — Michał Żołnieruk
– Michał Żołnieruk, Commented Apr 10, 2018 at 6:49
Refer to here and here

ColeX
– ColeX

2018-04-10 07:24:50 +00:00
Commented Apr 10, 2018 at 7:24 — ColeX
– ColeX, Commented Apr 10, 2018 at 7:24

Michał Żołnieruk · Accepted Answer · 2018-04-10 08:22:27Z

4

One solution to trigger C# method from website shown in WebView compontent is to:

1) Initialize a navigation to a website in your web code, for example

http://scancode/providedBarCode

2) Then you can override a webview method which is called before navigation actually happens. You can intercept a call there with parameters and ignore the actual navigation

Xamarin Forms (Navigating method of WebView)

webview.Navigating += (s, e) =>
{
    if (e.Url.StartsWith("http://scancode/"))
    {
        var parameter = e.Url.Split(new[] { "scancode/" }, StringSplitOptions.None)[1];
        // parameter will be providedBarCode

        // perform your logic here

        // cancel the actual navigation
        e.Cancel = true;
    }
};

Xamarin iOS (ShouldStartLoad method of UIWebView)

webViewControl.ShouldStartLoad = (webView, request, navType) =>
{
    var path = request.Url.AbsoluteString;
    if (path.StartsWith("http://scancode/"))
    {
        var parameter = path.Split(new[] { "scancode/" }, StringSplitOptions.None)[1];
        // parameter will be providedBarCode

        // perform your logic here

        // cancel the actual navigation
        return false;
    }

    return true;
}

edited Apr 10, 2018 at 8:22

answered Apr 9, 2018 at 15:17

Michał Żołnieruk

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6 Comments

NagendraBabu Over a year ago

HI Michal, Thank you so much for your response for my question.

NagendraBabu Over a year ago

HI Michal, Thank you so much for your quick response for my question.i am unable to find Navigating event for UIWebView on Xamarin iOS and also i would like to mention is there is button in html.i would like call C# function(CSharp.ScanBarcode('txtBarcode', 'setBarcodeInTextField') onClick event of button.

Michał Żołnieruk Over a year ago

I edited my answer with Xamarin.iOS code snipper. Put the code which you want to call above "return false", you have access there to your parameter.

Michał Żołnieruk Over a year ago

@NagendraBabu that's great :) please accept my answer, so others can see that it's a good solution to this kind of problems

NagendraBabu Over a year ago

i found one more best solution for calling c# method from javascript in UIWebview Xamarin iOS is from developer.xamarin.com/api/type/…

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