[iOS] Fix FlyoutPage does not respond to changes in the FlyoutLayoutBehavior property (#28884)

* Fix added

* fix updated

* test added

* test modified

* null check added

Author: devanathan-vaithiyanathan

src/Controls/src/Core/Compatibility/Handlers/FlyoutPage/iOS/PhoneFlyoutPageRenderer.cs

@@ -366,6 +366,8 @@ void HandlePropertyChanged(object sender, PropertyChangedEventArgs e)
 				UpdateBackground();
 			else if (e.PropertyName == PlatformConfiguration.iOSSpecific.FlyoutPage.ApplyShadowProperty.PropertyName)
 				UpdateApplyShadow(((FlyoutPage)Element).OnThisPlatform().GetApplyShadow());
+			else if (e.PropertyName == Microsoft.Maui.Controls.FlyoutPage.FlyoutLayoutBehaviorProperty.PropertyName) 
+				UpdateFlyoutLayoutBehaviorChanges();				
 			else if (e.PropertyName == PlatformConfiguration.iOSSpecific.Page.PrefersHomeIndicatorAutoHiddenProperty.PropertyName ||
 					 e.PropertyName == PlatformConfiguration.iOSSpecific.Page.PrefersStatusBarHiddenProperty.PropertyName)
 				UpdatePageSpecifics();
@@ -476,6 +478,26 @@ void LayoutChildren(bool animated)
 				UpdateClickOffViewFrame();
 		}
 
+		void UpdateFlyoutLayoutBehaviorChanges()
+		{
+			LayoutChildren(true);
+            FlyoutPage flyoutPage = Element as FlyoutPage;
+			if (flyoutPage == null) 
+				return;
+            FlyoutLayoutBehavior flyoutBehavior = FlyoutPage.FlyoutLayoutBehavior;
+            bool shouldPresent = FlyoutPageController.ShouldShowSplitMode;
+            if (flyoutBehavior == FlyoutLayoutBehavior.Popover || flyoutBehavior == FlyoutLayoutBehavior.Default)
+            {
+                shouldPresent = false;
+            }
+ 
+            if (shouldPresent != flyoutPage.IsPresented)
+            {
+                ((IElementController)Element).SetValueFromRenderer(FlyoutPage.IsPresentedProperty, shouldPresent);
+                UpdateLeftBarButton();
+            }
+		}
+
 		void PackContainers()
 		{
 			_detailController.View.BackgroundColor = new UIColor(1, 1, 1, 1);

src/Controls/tests/TestCases.HostApp/Issues/Issue18158.cs

@@ -0,0 +1,56 @@
+using System.Collections.ObjectModel;
+using System.Collections.Specialized;
+using System.ComponentModel;
+
+namespace Maui.Controls.Sample.Issues;
+
+[Issue(IssueTracker.Github, 18158, "FlyoutPage does not respond to changes in the FlyoutLayoutBehavior property", PlatformAffected.iOS)]
+public class Issue18158 : TestFlyoutPage
+{
+	Button _button;
+	protected override void Init()
+	{
+		_button = new Button{ Text="Click", AutomationId = "Button"};
+		FlyoutLayoutBehavior = FlyoutLayoutBehavior.Split;
+		// Define the Flyout page
+		Flyout = new ContentPage
+		{
+			Title = "Menu",
+			
+			Content = new StackLayout
+			{
+				Children =
+				{
+					_button,
+				}
+			}
+		};
+
+		_button.Clicked += (s,e) =>
+		{
+			if (this.FlyoutLayoutBehavior == FlyoutLayoutBehavior.Split)
+			{
+				this.FlyoutLayoutBehavior = FlyoutLayoutBehavior.Popover;
+			}
+			else
+			{
+				this.FlyoutLayoutBehavior = FlyoutLayoutBehavior.Split;
+			}
+		};
+
+
+		// Define the Detail page
+		Detail = new NavigationPage(new ContentPage
+		{
+			Title = "Detail Page",
+			Content = new StackLayout
+			{
+				Children =
+				{
+					new Label { Text = "Welcome to the Detail Page!", AutomationId = "Label" },
+				}
+			}
+		});
+
+	}
+}

src/Controls/tests/TestCases.Shared.Tests/Tests/Issues/Issue18158.cs

@@ -0,0 +1,27 @@
+#if TEST_FAILS_ON_ANDROID && TEST_FAILS_ON_IOS    //FlyoutLayoutBehavior changes are not supported on Android and iOS
+using NUnit.Framework;
+using UITest.Appium;
+using UITest.Core;
+
+namespace Microsoft.Maui.TestCases.Tests.Issues;
+
+public class Issue18158 : _IssuesUITest
+{
+	public Issue18158(TestDevice device)
+		: base(device)
+	{ }
+
+	public override string Issue => "FlyoutPage does not respond to changes in the FlyoutLayoutBehavior property";
+
+	[Test]
+	[Category(UITestCategories.FlyoutPage)]
+	public void VerifyFlyoutLayoutBehaviorChanges()
+	{
+		App.WaitForElement("Button");
+		App.Tap("Button");
+		App.WaitForElement("Label");
+		App.WaitForNoElement("Button");
+	}
+}
+
+#endif