Expose starting and finished load events in WebView

src/Microsoft.MobileBlazorBindings/Elements/Handlers/WebViewHandler.cs

@@ -1,6 +1,7 @@
 // Copyright (c) Microsoft Corporation.
 // Licensed under the MIT license.
 
+using System;
 using Microsoft.MobileBlazorBindings.Core;
 using Microsoft.MobileBlazorBindings.WebView.Elements;
 using XF = Xamarin.Forms;
@@ -12,6 +13,8 @@ public class WebViewHandler : ViewHandler
         public WebViewExtended Control { get; }
 
         private ulong _onWebMessageReceivedEventHandlerId;
+        private ulong _onNavigationStartingEventHandlerId;
+        private ulong _onNavigationFinishedEventHandlerId;
 
         public WebViewHandler(NativeComponentRenderer renderer, WebViewExtended control)
             : base(renderer, control)
@@ -30,6 +33,33 @@ public WebViewHandler(NativeComponentRenderer renderer, WebViewExtended control)
                     renderer.Dispatcher.InvokeAsync(() => renderer.DispatchEventAsync(_onWebMessageReceivedEventHandlerId, null, new WebView.WebMessageEventArgs { Message = message }));
                 }
             };
+
+            ConfigureEvent(
+                eventName: "onnavigationstarting",
+                setId: id => _onNavigationStartingEventHandlerId = id,
+                clearId: id => { if (_onNavigationStartingEventHandlerId == id) { _onNavigationStartingEventHandlerId = 0; } });
+
+            Control.OnNavigationStarting += (sender, uri) =>
+            {
+                if (_onNavigationStartingEventHandlerId != default)
+                {
+                    renderer.Dispatcher.InvokeAsync(() => renderer.DispatchEventAsync(_onNavigationStartingEventHandlerId, null, new WebView.NavigationEventArgs() { Uri = uri }));
+                }
+            };
+
+            ConfigureEvent(
+                eventName: "onnavigationfinished",
+                setId: id => _onNavigationFinishedEventHandlerId = id,
+                clearId: id => { if (_onNavigationFinishedEventHandlerId == id) { _onNavigationFinishedEventHandlerId = 0; } });
+
+            Control.OnNavigationFinished += (sender, uri) =>
+            {
+                if (_onNavigationFinishedEventHandlerId != default)
+                {
+                    renderer.Dispatcher.InvokeAsync(() => renderer.DispatchEventAsync(_onNavigationFinishedEventHandlerId, null, new WebView.NavigationEventArgs() { Uri = uri }));
+                }
+            };
+
         }
 
         public override void ApplyAttribute(ulong attributeEventHandlerId, string attributeName, object attributeValue, string attributeEventUpdatesAttributeName)

src/Microsoft.MobileBlazorBindings/Elements/WebView.cs

@@ -23,6 +23,8 @@ static WebView()
 
         [Parameter] public XF.WebViewSource Source { get; set; }
         [Parameter] public EventCallback<string> OnWebMessageReceived { get; set; }
+        [Parameter] public EventCallback<Uri> OnNavigationStarting { get; set; }
+        [Parameter] public EventCallback<Uri> OnNavigationFinished { get; set; }
 
         public void SendMessage(string message)
         {
@@ -34,6 +36,8 @@ protected override void RenderAttributes(AttributesBuilder builder)
             base.RenderAttributes(builder);
 
             builder.AddAttribute("onwebmessagereceived", EventCallback.Factory.Create<WebMessageEventArgs>(this, HandleOnWebMessageReceived));
+            builder.AddAttribute("onnavigationstarting", EventCallback.Factory.Create<NavigationEventArgs>(this, HandleOnNavigationStarting));
+            builder.AddAttribute("onnavigationfinished", EventCallback.Factory.Create<NavigationEventArgs>(this, HandleOnNavigationFinished));
 
             switch (Source)
             {
@@ -49,9 +53,20 @@ protected override void RenderAttributes(AttributesBuilder builder)
         private Task HandleOnWebMessageReceived(WebMessageEventArgs args)
             => OnWebMessageReceived.InvokeAsync(args.Message);
 
+        private Task HandleOnNavigationStarting(NavigationEventArgs args)
+            => OnNavigationStarting.InvokeAsync(args.Uri);
+
+        private Task HandleOnNavigationFinished(NavigationEventArgs args)
+            => OnNavigationFinished.InvokeAsync(args.Uri);
+
         internal class WebMessageEventArgs : EventArgs
         {
             public string Message { get; set; }
         }
+
+        internal class NavigationEventArgs : EventArgs
+        {
+            public Uri Uri { get; set; }
+        }
     }
 }