Fix CarouselView ItemsLayout Runtime Updates (#29447)

* Fixed the issue for dynamic changes of ItemsLayout property

* Simplified the fix

* Removed unwanted lines

* Modified the fix

* Added null check

* Added a test case and snapshots

* Modified a test case

* Modified the public api to internal

Author: Shalini-Ashokan

src/Controls/src/Core/Handlers/Items/CarouselViewHandler.Android.cs

@@ -53,6 +53,15 @@ public static void MapCurrentItem(CarouselViewHandler handler, CarouselView caro
 			(handler.PlatformView as IMauiCarouselRecyclerView).UpdateFromCurrentItem();
 		}
 
+		// TODO: Change the modifier to public in .NET 10.
+		internal static void MapItemsLayout(CarouselViewHandler handler, CarouselView carouselView)
+		{
+			if (handler.PlatformView is IMauiRecyclerView<CarouselView> recyclerView)
+			{
+				recyclerView.UpdateLayoutManager();
+			}
+		}
+
 		public override Size GetDesiredSize(double widthConstraint, double heightConstraint)
 		{
 			_widthConstraint = widthConstraint;

src/Controls/src/Core/Handlers/Items/CarouselViewHandler.cs

@@ -14,7 +14,7 @@ public CarouselViewHandler(PropertyMapper mapper = null) : base(mapper ?? Mapper
 
 		public static PropertyMapper<CarouselView, CarouselViewHandler> Mapper = new(ItemsViewMapper)
 		{
-#if TIZEN
+#if TIZEN || ANDROID
 			[Controls.CarouselView.ItemsLayoutProperty.PropertyName] = MapItemsLayout,
 #endif
 			[Controls.CarouselView.IsSwipeEnabledProperty.PropertyName] = MapIsSwipeEnabled,

src/Controls/src/Core/Handlers/Items2/CarouselViewHandler2.iOS.cs

@@ -27,7 +27,8 @@ public CarouselViewHandler2(PropertyMapper mapper = null) : base(mapper ?? Mappe
 			[Controls.CarouselView.PeekAreaInsetsProperty.PropertyName] = MapPeekAreaInsets,
 			[Controls.CarouselView.IsBounceEnabledProperty.PropertyName] = MapIsBounceEnabled,
 			[Controls.CarouselView.PositionProperty.PropertyName] = MapPosition,
-			[Controls.CarouselView.CurrentItemProperty.PropertyName] = MapCurrentItem
+			[Controls.CarouselView.CurrentItemProperty.PropertyName] = MapCurrentItem,
+			[Controls.CarouselView.ItemsLayoutProperty.PropertyName] = MapItemsLayout,
 		};
 	}
 
@@ -190,6 +191,12 @@ public static void MapIsBounceEnabled(CarouselViewHandler2 handler, CarouselView
 			handler.Controller.CollectionView.Bounces = carouselView.IsBounceEnabled;
 		}
 
+		// TODO: Change the modifier to public in .NET 10.
+		internal static void MapItemsLayout(CarouselViewHandler2 handler, CarouselView carouselView)
+		{
+			handler?.UpdateLayout();
+		}
+
 		public static void MapPeekAreaInsets(CarouselViewHandler2 handler, CarouselView carouselView)
 		{
 			handler.UpdateLayout();

src/Controls/tests/TestCases.Android.Tests/snapshots/android/VerifyCarouselLayoutOrientationChange.png

@@ -0,0 +1,73 @@
+using System.Collections.ObjectModel;
+
+namespace Maui.Controls.Sample.Issues;
+[Issue(IssueTracker.Github, 29372, "CarouselView ItemsLayout Not Updating at Runtime", PlatformAffected.All)]
+public partial class Issue29372 : ContentPage
+{
+	public Issue29372()
+	{
+		var verticalStackLayout = new VerticalStackLayout();
+		var carouselItems = new ObservableCollection<string>
+		{
+			"Item 0",
+			"Item 1",
+			"Item 2",
+			"Item 3",
+			"Item 4",
+		};
+
+		CarouselView2 carouselView = new CarouselView2
+		{
+			ItemsSource = carouselItems,
+			AutomationId = "carouselview",
+			ItemsLayout = new LinearItemsLayout(ItemsLayoutOrientation.Horizontal),
+			PeekAreaInsets = new Thickness(0, 100),
+			HeightRequest = 300,
+			Loop = false,
+			ItemTemplate = new DataTemplate(() =>
+			{
+				var grid = new Grid
+				{
+					Padding = 10
+				};
+
+				var label = new Label
+				{
+					VerticalOptions = LayoutOptions.Center,
+					HorizontalOptions = LayoutOptions.Center,
+					FontSize = 18,
+				};
+				label.SetBinding(Label.TextProperty, ".");
+				label.SetBinding(Label.AutomationIdProperty, ".");
+
+				grid.Children.Add(label);
+				return grid;
+			}),
+			HorizontalOptions = LayoutOptions.Fill,
+		};
+
+		var button = new Button
+		{
+			Text = "Change Items Layout",
+			AutomationId = "ChangeItemsLayoutButton",
+			Margin = new Thickness(20),
+		};
+
+		var label = new Label
+		{
+			Text = "The test is passed if the items are displayed in a vertical orientation.",
+			HorizontalOptions = LayoutOptions.Center,
+			Padding = new Thickness(20),
+		};
+
+		button.Clicked += (sender, e) =>
+		{
+			carouselView.ItemsLayout = new LinearItemsLayout(ItemsLayoutOrientation.Vertical);
+		};
+
+		verticalStackLayout.Children.Add(label);
+		verticalStackLayout.Children.Add(carouselView);
+		verticalStackLayout.Children.Add(button);
+		Content = verticalStackLayout;
+	}
+}

src/Controls/tests/TestCases.HostApp/Issues/Issue29372.cs

@@ -0,0 +1,24 @@
+#if TEST_FAILS_ON_WINDOWS // Related issue for windows: https://github.com/dotnet/maui/issues/29445
+using NUnit.Framework;
+using UITest.Appium;
+using UITest.Core;
+
+namespace Microsoft.Maui.TestCases.Tests.Issues;
+public class Issue29372 : _IssuesUITest
+{
+    public override string Issue => "CarouselView ItemsLayout Not Updating at Runtime";
+
+    public Issue29372(TestDevice device)
+    : base(device)
+    { }
+
+    [Test]
+    [Category(UITestCategories.CarouselView)]
+    public void VerifyCarouselLayoutOrientationChange()
+    {
+        App.WaitForElement("carouselview");
+        App.Tap("ChangeItemsLayoutButton");
+        VerifyScreenshot();
+    }
+}
+#endif