Hasan A Yousef Hasan A Yousef - 2 months ago 16
Android Question

Calling C# from JavaScript in Xamarin

Trying to test this example, but found it not working with me, I use API19, and my code is:

using System;
using Android.App;
using Android.Content;
using Android.Runtime;
using Android.Views;
using Android.Widget;
using Android.OS;
using Android.Webkit;
using Java.Interop;

namespace App3
{
[Activity(Label = "App3", MainLauncher = true, Icon = "@drawable/icon")]
public class MainActivity : Activity
{
int count = 1;

const string html = @"
<html>
<body>
<p>Demo calling C# from JavaScript</p>
<button type=""button"" onClick=""CSharp.ShowToast()"">Call C# </button>
</body>
</html>";

protected override void OnCreate(Bundle bundle)
{
base.OnCreate(bundle);

// Set our view from the "main" layout resource
SetContentView(Resource.Layout.Main);

// Get our button from the layout resource,
// and attach an event to it
Button button = FindViewById<Button>(Resource.Id.MyButton);

WebView localWebView = FindViewById<WebView>(Resource.Id.LocalWebView);
localWebView.SetWebViewClient(new WebViewClient()); // stops request going to Web Browser
localWebView.Settings.JavaScriptEnabled = true;
// localWebView.LoadUrl("http://developer.xamarin.com");
// localWebView.LoadUrl("file:///android_asset/index.html");
localWebView.LoadData(html, "text/html", null);

button.Click += delegate { button.Text = string.Format("{0} clicks!", count++); };
}
}
class MyJSInterface : Java.Lang.Object
{
Context context;

public MyJSInterface(Context context)
{
this.context = context;
}

[Export]
[JavascriptInterface]
public void ShowToast()
{
Toast.MakeText(context, "Hello from C#", ToastLength.Short).Show();
}
}
}


What is the mistake I've here!

Note: I already Added a reference to Mono.Android.Export (so you can use the [Export] annotation):

Answer

You need to add an instance of the MyJavascriptInterface to the localWebView before loading the HTML:

WebView localWebView = FindViewById<WebView>(Resource.Id.LocalWebView);
localWebView.SetWebViewClient(new WebViewClient()); // stops request going to Web Browser
localWebView.Settings.JavaScriptEnabled = true;

// Add an instance of the Javascript interface named "CSharp"
localWebView.AddJavascriptInterface(new MyJSInterface(this), "CSharp");

localWebView.LoadData(html, "text/html", null);
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