feat: Support for WebMessageReceived on Android

src/Uno.UI/UI/Xaml/Controls/WebView/Core/CoreWebView2.cs

@@ -129,6 +129,8 @@ public partial class CoreWebView2
 
 	internal void RaiseHistoryChanged() => HistoryChanged?.Invoke(this, null);
 
+	internal void RaiseWebMessageReceived(string message) => WebMessageReceived?.Invoke(this, new(message));
+
 	internal void SetHistoryProperties(bool canGoBack, bool canGoForward)
 	{
 		CanGoBack = canGoBack;

src/Uno.UI/UI/Xaml/Controls/WebView/Core/CoreWebView2WebMessageReceivedEventArgs.cs

@@ -5,7 +5,7 @@ namespace Microsoft.Web.WebView2.Core;
 /// </summary>
 public partial class CoreWebView2WebMessageReceivedEventArgs
 {
-	private CoreWebView2WebMessageReceivedEventArgs(string webMessageAsJson)
+	internal CoreWebView2WebMessageReceivedEventArgs(string webMessageAsJson)
 	{
 		WebMessageAsJson = webMessageAsJson;
 	}

src/Uno.UI/UI/Xaml/Controls/WebView/Native/Android/NativeWebViewWrapper.Android.cs

@@ -40,6 +40,7 @@ internal class NativeWebViewWrapper : INativeWebView
 		_webView.Settings.SetSupportZoom(true);
 		_webView.Settings.LoadWithOverviewMode = true;
 		_webView.Settings.UseWideViewPort = true;
+		_webView.AddJavascriptInterface(new UnoWebMessageHandler(this), "unoWebMessageHandler");
 
 		//Allow ThirdPartyCookies by default only on Android 5.0 and UP
 		if (Android.OS.Build.VERSION.SdkInt >= Android.OS.BuildVersionCodes.Lollipop)
@@ -199,5 +200,13 @@ internal class NativeWebViewWrapper : INativeWebView
 		_webView.HorizontalScrollBarEnabled = scrollingEnabled;
 		_webView.VerticalScrollBarEnabled = scrollingEnabled;
 	}
+
+	internal void OnWebMessageReceived(string message)
+	{
+		if (_coreWebView.Settings.IsWebMessageEnabled)
+		{
+			_coreWebView.RaiseWebMessageReceived(message);
+		}
+	}
 }
 

src/Uno.UI/UI/Xaml/Controls/WebView/Native/Android/UnoWebViewHandler.Android.cs

+using Android.Webkit;
+using Java.Interop;
+
+namespace Uno.UI.Xaml.Controls;
+
+internal class UnoWebMessageHandler : Java.Lang.Object
+{
+	private readonly NativeWebViewWrapper _nativeWebView;
+
+	public UnoWebMessageHandler(NativeWebViewWrapper wrapper)
+	{
+		_nativeWebView = wrapper;
+	}
+
+	[Export]
+	[JavascriptInterface]
+	public void postMessage(string message) => _nativeWebView?.OnWebMessageReceived(message);
+}