Add demo exception handling to HybridWebView sample

Copilot · mattleibow · mattleibow · commit 74326b6fecd9 · 2025-09-09T03:35:41.000+02:00
- Added ThrowException and ThrowExceptionAsync methods to demonstrate new functionality
- Added JavaScript functions to test and showcase exception catching
- Added UI buttons to trigger exception handling tests
- Updated sample to show both error and success scenarios

Co-authored-by: mattleibow &lt;1096616+mattleibow@users.noreply.github.com&gt;
diff --git a/src/Controls/samples/Controls.Sample/Pages/Controls/HybridWebViewPage.xaml.cs b/src/Controls/samples/Controls.Sample/Pages/Controls/HybridWebViewPage.xaml.cs
@@ -153,6 +153,21 @@ public async Task<SyncReturn> DoAsyncWorkParamsReturn(int i, string s)
 					Value = i,
 				};
 			}
+
+			// Demo method that throws an exception to showcase error handling
+			public void ThrowException()
+			{
+				Debug.WriteLine("ThrowException called - about to throw");
+				throw new InvalidOperationException("This is a test exception thrown from C# code!");
+			}
+
+			// Demo async method that throws an exception
+			public async Task<string> ThrowExceptionAsync()
+			{
+				Debug.WriteLine("ThrowExceptionAsync called - about to throw");
+				await Task.Delay(100);
+				throw new ArgumentException("This is an async test exception thrown from C# code!");
+			}
 		}
 
 		public class SyncReturn
diff --git a/src/Controls/samples/Controls.Sample/Resources/Raw/HybridSamplePage/index.html b/src/Controls/samples/Controls.Sample/Resources/Raw/HybridSamplePage/index.html
@@ -93,6 +93,32 @@
             LogMessage("Invoked DoAsyncWorkParamsReturn, return value: message=" + retValue.Message + ", value=" + retValue.Value);
         }
 
+        // Demo functions to test exception handling
+        async function InvokeThrowException() {
+            LogMessage("Invoking ThrowException");
+            try {
+                await window.HybridWebView.InvokeDotNet('ThrowException');
+                LogMessage("ThrowException unexpectedly succeeded!");
+            } catch (ex) {
+                LogMessage("Caught exception from ThrowException: " + ex.message);
+                LogMessage("Exception type: " + (ex.dotNetErrorType || "Unknown"));
+                if (ex.dotNetStackTrace) {
+                    LogMessage("Stack trace: " + ex.dotNetStackTrace.substring(0, 200) + "...");
+                }
+            }
+        }
+
+        async function InvokeThrowExceptionAsync() {
+            LogMessage("Invoking ThrowExceptionAsync");
+            try {
+                const result = await window.HybridWebView.InvokeDotNet('ThrowExceptionAsync');
+                LogMessage("ThrowExceptionAsync unexpectedly succeeded with result: " + result);
+            } catch (ex) {
+                LogMessage("Caught async exception from ThrowExceptionAsync: " + ex.message);
+                LogMessage("Exception type: " + (ex.dotNetErrorType || "Unknown"));
+            }
+        }
+
     </script>
 </head>
 <body>
@@ -114,6 +140,11 @@
         <button onclick="InvokeDoAsyncWorkReturn()">Call C# async method (no params) and get simple return value</button>
         <button onclick="InvokeDoAsyncWorkParamsReturn()">Call C# async method (params) and get complex return value</button>
     </div>
+    <div>
+        <strong>Exception Handling Tests:</strong>
+        <button onclick="InvokeThrowException()">Test C# Exception Handling</button>
+        <button onclick="InvokeThrowExceptionAsync()">Test C# Async Exception Handling</button>
+    </div>
     <div>
         Log: <textarea readonly id="messageLog" style="width: 80%; height: 10em;"></textarea>
     </div>
diff --git a/src/Core/src/Handlers/Button/ButtonHandler.Android.cs b/src/Core/src/Handlers/Button/ButtonHandler.Android.cs
@@ -153,8 +153,7 @@ static void OnClick(IButton? button, AView? v)
 
 		void OnNativeViewFocusChange(object? sender, AView.FocusChangeEventArgs e)
 		{
-			if (VirtualView != null)
-				VirtualView.IsFocused = e.HasFocus;
+			VirtualView?.IsFocused = e.HasFocus;
 		}
 
 		void OnPlatformViewLayoutChange(object? sender, AView.LayoutChangeEventArgs e)
diff --git a/src/Core/src/Handlers/CheckBox/CheckBoxHandler.Android.cs b/src/Core/src/Handlers/CheckBox/CheckBoxHandler.Android.cs
@@ -46,8 +46,7 @@ public static partial void MapForeground(ICheckBoxHandler handler, ICheckBox che
 
 		void OnCheckedChange(object? sender, CompoundButton.CheckedChangeEventArgs e)
 		{
-			if (VirtualView != null)
-				VirtualView.IsChecked = e.IsChecked;
+			VirtualView?.IsChecked = e.IsChecked;
 		}
 	}
 }
diff --git a/src/Core/src/Handlers/DatePicker/DatePickerHandler.Android.cs b/src/Core/src/Handlers/DatePicker/DatePickerHandler.Android.cs
@@ -78,10 +78,7 @@ protected virtual DatePickerDialog CreateDatePickerDialog(int year, int month, i
 		{
 			var dialog = new DatePickerDialog(Context!, (o, e) =>
 			{
-				if (VirtualView is not null)
-				{
-					VirtualView.Date = e.Date;
-				}
+				VirtualView?.Date = e.Date;
 			}, year, month, day);
 
 			dialog.DismissEvent += OnDialogDismiss;
diff --git a/src/Core/src/Handlers/FlyoutView/FlyoutViewHandler.Android.cs b/src/Core/src/Handlers/FlyoutView/FlyoutViewHandler.Android.cs
@@ -281,7 +281,7 @@ internal class WindowsListener : Java.Lang.Object, IOnApplyWindowInsetsListener
 					layoutParams.TopMargin = topInset;
 					v.LayoutParameters = layoutParams;
 				}
-				
+
 				return WindowInsetsCompat.Consumed;
 			}
 		}
diff --git a/src/Core/src/Handlers/HybridWebView/HybridWebViewHandler.cs b/src/Core/src/Handlers/HybridWebView/HybridWebViewHandler.cs
@@ -197,7 +197,7 @@ void MessageReceived(string rawMessage)
 			catch (Exception ex)
 			{
 				MauiContext?.CreateLogger<HybridWebViewHandler>()?.LogError(ex, "An error occurred while invoking a .NET method from JavaScript: {ErrorMessage}", ex.Message);
-				
+
 				// Return error response instead of null so JavaScript can handle the error
 				var errorResult = CreateErrorResult(ex);
 				var errorJson = JsonSerializer.Serialize(errorResult, HybridWebViewHandlerJsonContext.Default.DotNetInvokeResult);
diff --git a/src/Core/src/Handlers/ImageButton/ImageButtonHandler.Android.cs b/src/Core/src/Handlers/ImageButton/ImageButtonHandler.Android.cs
@@ -69,8 +69,7 @@ public static void MapPadding(IImageButtonHandler handler, IImageButton imageBut
 
 		void OnFocusChange(object? sender, View.FocusChangeEventArgs e)
 		{
-			if (VirtualView != null)
-				VirtualView.IsFocused = e.HasFocus;
+			VirtualView?.IsFocused = e.HasFocus;
 		}
 
 		void OnTouch(object? sender, View.TouchEventArgs e)
diff --git a/src/Core/src/Handlers/SearchBar/SearchBarHandler.Android.cs b/src/Core/src/Handlers/SearchBar/SearchBarHandler.Android.cs
@@ -165,8 +165,7 @@ public void OnFocusChange(View? v, bool hasFocus)
 
 				var virtualView = Handler.VirtualView;
 
-				if (virtualView != null)
-					virtualView.IsFocused = hasFocus;
+				virtualView?.IsFocused = hasFocus;
 			}
 		}
 	}
diff --git a/src/Core/src/Handlers/TimePicker/TimePickerHandler.Android.cs b/src/Core/src/Handlers/TimePicker/TimePickerHandler.Android.cs
@@ -133,10 +133,7 @@ void ShowPickerDialog(TimeSpan? time)
 			_dialog = CreateTimePickerDialog(hour, minute);
 			_dialog.Show();
 
-			if (VirtualView is not null)
-			{
-				VirtualView.IsOpen = true;
-			}
+			VirtualView?.IsOpen = true;
 		}
 
 		void HidePickerDialog()
diff --git a/src/Core/src/Handlers/View/ViewHandler.Android.cs b/src/Core/src/Handlers/View/ViewHandler.Android.cs
@@ -251,10 +251,7 @@ public static void MapContextFlyout(IViewHandler handler, IView view)
 
 		void OnPlatformViewFocusChange(object? sender, PlatformView.FocusChangeEventArgs e)
 		{
-			if (VirtualView != null)
-			{
-				VirtualView.IsFocused = e.HasFocus;
-			}
+			VirtualView?.IsFocused = e.HasFocus;
 		}
 	}
 }
diff --git a/src/Core/src/Handlers/Window/WindowHandler.Android.cs b/src/Core/src/Handlers/Window/WindowHandler.Android.cs
@@ -136,7 +136,7 @@ internal class WindowsListener : Java.Lang.Object, IOnApplyWindowInsetsListener
 
 				// Apply top inset only to AppBarLayout to allow content behind it
 				appBarLayout?.SetPadding(0, topInset, 0, 0);
-				
+
 				// Apply side and bottom insets to root view, but not top
 				v.SetPadding(leftInset, 0, rightInset, bottomInset);
 
@@ -155,7 +155,7 @@ internal class WindowsListener : Java.Lang.Object, IOnApplyWindowInsetsListener
 					displayCutout?.Right ?? 0,
 					0
 				) ?? Insets.None;
-				
+
 				return new WindowInsetsCompat.Builder(insets)
 					?.SetInsets(WindowInsetsCompat.Type.SystemBars(), newSystemBars)
 					?.SetInsets(WindowInsetsCompat.Type.DisplayCutout(), newDisplayCutout)
diff --git a/src/Core/src/Platform/Android/MauiPageControl.cs b/src/Core/src/Platform/Android/MauiPageControl.cs
@@ -154,9 +154,7 @@ void UpdateShapes()
 			shape.SetIntrinsicHeight((int)Context.ToPixels(indicatorSize));
 			shape.SetIntrinsicWidth((int)Context.ToPixels(indicatorSize));
 
-			if (shape.Paint != null)
-#pragma warning disable CA1416 // https://github.com/xamarin/xamarin-android/issues/6962
-				shape.Paint.Color = color;
+			shape.Paint?.Color = color;
 #pragma warning restore CA1416
 
 			return shape;
diff --git a/src/Core/src/Platform/Android/MauiSwipeView.cs b/src/Core/src/Platform/Android/MauiSwipeView.cs
@@ -1320,8 +1320,7 @@ static void ExecuteSwipeItem(ISwipeItem item)
 
 		void EnableParentGesture(bool isGestureEnabled)
 		{
-			if (_viewPagerParent != null)
-				_viewPagerParent.EnableGesture = isGestureEnabled;
+			_viewPagerParent?.EnableGesture = isGestureEnabled;
 		}
 
 		internal void OnOpenRequested(SwipeViewOpenRequest e)
diff --git a/src/Core/src/Platform/Android/MauiWebView.cs b/src/Core/src/Platform/Android/MauiWebView.cs
@@ -17,8 +17,7 @@ public MauiWebView(WebViewHandler handler, Context context) : base(context)
 
 		void IWebViewDelegate.LoadHtml(string? html, string? baseUrl)
 		{
-			if (_handler != null)
-				_handler.CurrentNavigationEvent = WebNavigationEvent.NewPage;
+			_handler?.CurrentNavigationEvent = WebNavigationEvent.NewPage;
 
 			LoadDataWithBaseURL(baseUrl ?? AssetBaseUrl, html ?? string.Empty, "text/html", "UTF-8", null);
 		}
@@ -27,10 +26,7 @@ void IWebViewDelegate.LoadUrl(string? url)
 		{
 			if (!_handler.NavigatingCanceled(url))
 			{
-				if (_handler != null)
-				{
-					_handler.CurrentNavigationEvent = WebNavigationEvent.NewPage;
-				}
+				_handler?.CurrentNavigationEvent = WebNavigationEvent.NewPage;
 
 				if (url is not null && !url.StartsWith('/') && !Uri.TryCreate(url, UriKind.Absolute, out _))
 				{
diff --git a/src/Core/src/Platform/Android/PickerExtensions.cs b/src/Core/src/Platform/Android/PickerExtensions.cs
@@ -57,8 +57,7 @@ internal static void UpdateFlowDirection(this AppCompatAlertDialog alertDialog,
 			// Propagate the MauiPicker LayoutDirection to the AlertDialog
 			var dv = alertDialog.Window?.DecorView;
 
-			if (dv is not null)
-				dv.LayoutDirection = platformLayoutDirection;
+			dv?.LayoutDirection = platformLayoutDirection;
 
 			var lv = alertDialog?.ListView;
 
diff --git a/src/Core/src/Platform/Android/SearchViewExtensions.cs b/src/Core/src/Platform/Android/SearchViewExtensions.cs
@@ -174,10 +174,7 @@ public static void UpdateIsEnabled(this SearchView searchView, ISearchBar search
 			if (editText == null)
 				return;
 
-			if (editText != null)
-			{
-				editText.Enabled = searchBar.IsEnabled;
-			}
+			editText?.Enabled = searchBar.IsEnabled;
 		}
 
 		public static void UpdateKeyboard(this SearchView searchView, ISearchBar searchBar)
diff --git a/src/Core/src/Platform/Android/StepperHandlerManager.cs b/src/Core/src/Platform/Android/StepperHandlerManager.cs
@@ -64,11 +64,9 @@ public static void UpdateButtons<TButton>(IStepper stepper, TButton? downButton,
 			where TButton : AButton
 		{
 			// NOTE: a value of `null` means that we are forcing an update
-			if (downButton != null)
-				downButton.Enabled = stepper.IsEnabled && stepper.Value > stepper.Minimum;
+			downButton?.Enabled = stepper.IsEnabled && stepper.Value > stepper.Minimum;
 
-			if (upButton != null)
-				upButton.Enabled = stepper.IsEnabled && stepper.Value < stepper.Maximum;
+			upButton?.Enabled = stepper.IsEnabled && stepper.Value < stepper.Maximum;
 		}
 
 		class StepperListener : Java.Lang.Object, AView.IOnClickListener
diff --git a/src/Core/src/Primitives/SafeAreaEdges.cs b/src/Core/src/Primitives/SafeAreaEdges.cs
@@ -84,7 +84,7 @@ internal static bool IsContainer(SafeAreaRegions region)
 				return false;
 			if (region == SafeAreaRegions.All)
 				return true;
-			return (region & SafeAreaRegions.Container) == SafeAreaRegions.Container;	
+			return (region & SafeAreaRegions.Container) == SafeAreaRegions.Container;
 		}
 
 		/// <summary>

Original file line number	Diff line number	Diff line change
`@@ -153,8 +153,7 @@ static void OnClick(IButton? button, AView? v)`
`153`	`153`
`154`	`154`	`void OnNativeViewFocusChange(object? sender, AView.FocusChangeEventArgs e)`
`155`	`155`	`{`
`156`		`- if (VirtualView != null)`
`157`		`- VirtualView.IsFocused = e.HasFocus;`
	`156`	`+ VirtualView?.IsFocused = e.HasFocus;`
`158`	`157`	`}`
`159`	`158`
`160`	`159`	`void OnPlatformViewLayoutChange(object? sender, AView.LayoutChangeEventArgs e)`
Original file line number	Diff line number	Diff line change
`@@ -46,8 +46,7 @@ public static partial void MapForeground(ICheckBoxHandler handler, ICheckBox che`
`46`	`46`
`47`	`47`	`void OnCheckedChange(object? sender, CompoundButton.CheckedChangeEventArgs e)`
`48`	`48`	`{`
`49`		`- if (VirtualView != null)`
`50`		`- VirtualView.IsChecked = e.IsChecked;`
	`49`	`+ VirtualView?.IsChecked = e.IsChecked;`
`51`	`50`	`}`
`52`	`51`	`}`
`53`	`52`	`}`
Original file line number	Diff line number	Diff line change
`@@ -78,10 +78,7 @@ protected virtual DatePickerDialog CreateDatePickerDialog(int year, int month, i`
`78`	`78`	`{`
`79`	`79`	`var dialog = new DatePickerDialog(Context!, (o, e) =>`
`80`	`80`	`{`
`81`		`- if (VirtualView is not null)`
`82`		`- {`
`83`		`- VirtualView.Date = e.Date;`
`84`		`- }`
	`81`	`+ VirtualView?.Date = e.Date;`
`85`	`82`	`}, year, month, day);`
`86`	`83`
`87`	`84`	`dialog.DismissEvent += OnDialogDismiss;`
Original file line number	Diff line number	Diff line change
`@@ -281,7 +281,7 @@ internal class WindowsListener : Java.Lang.Object, IOnApplyWindowInsetsListener`
`281`	`281`	`layoutParams.TopMargin = topInset;`
`282`	`282`	`v.LayoutParameters = layoutParams;`
`283`	`283`	`}`
`284`		`-`
	`284`	`+`
`285`	`285`	`return WindowInsetsCompat.Consumed;`
`286`	`286`	`}`
`287`	`287`	`}`
Original file line number	Diff line number	Diff line change
`@@ -197,7 +197,7 @@ void MessageReceived(string rawMessage)`
`197`	`197`	`catch (Exception ex)`
`198`	`198`	`{`
`199`	`199`	`MauiContext?.CreateLogger<HybridWebViewHandler>()?.LogError(ex, "An error occurred while invoking a .NET method from JavaScript: {ErrorMessage}", ex.Message);`
`200`		`-`
	`200`	`+`
`201`	`201`	`// Return error response instead of null so JavaScript can handle the error`
`202`	`202`	`var errorResult = CreateErrorResult(ex);`
`203`	`203`	`var errorJson = JsonSerializer.Serialize(errorResult, HybridWebViewHandlerJsonContext.Default.DotNetInvokeResult);`
Original file line number	Diff line number	Diff line change
`@@ -69,8 +69,7 @@ public static void MapPadding(IImageButtonHandler handler, IImageButton imageBut`
`69`	`69`
`70`	`70`	`void OnFocusChange(object? sender, View.FocusChangeEventArgs e)`
`71`	`71`	`{`
`72`		`- if (VirtualView != null)`
`73`		`- VirtualView.IsFocused = e.HasFocus;`
	`72`	`+ VirtualView?.IsFocused = e.HasFocus;`
`74`	`73`	`}`
`75`	`74`
`76`	`75`	`void OnTouch(object? sender, View.TouchEventArgs e)`
Original file line number	Diff line number	Diff line change
`@@ -165,8 +165,7 @@ public void OnFocusChange(View? v, bool hasFocus)`
`165`	`165`
`166`	`166`	`var virtualView = Handler.VirtualView;`
`167`	`167`
`168`		`- if (virtualView != null)`
`169`		`- virtualView.IsFocused = hasFocus;`
	`168`	`+ virtualView?.IsFocused = hasFocus;`
`170`	`169`	`}`
`171`	`170`	`}`
`172`	`171`	`}`