[iOS] - Resolved Proper Rendering of Dynamic Header/Footer Updates in CV2 (dotnet#28641)

* Fixed-Header-Footer-Issues-In-CV2

* Modified-Test

* Android-Specific Test Restriction

* Modified-fix

* Added-Comment

Author: prakashKannanSf3972

src/Controls/src/Core/Handlers/Items2/CollectionViewHandler2.iOS.cs

@@ -56,6 +56,8 @@ public CollectionViewHandler2(PropertyMapper mapper = null) : base(mapper ?? Map
 			[StructuredItemsView.FooterTemplateProperty.PropertyName] = MapFooterTemplate,
 			[StructuredItemsView.HeaderProperty.PropertyName] = MapHeaderTemplate,
 			[StructuredItemsView.FooterProperty.PropertyName] = MapFooterTemplate,
+			[GroupableItemsView.GroupHeaderTemplateProperty.PropertyName] = MapHeaderTemplate,
+			[GroupableItemsView.GroupFooterTemplateProperty.PropertyName] = MapFooterTemplate,
 		};
 	}
 

src/Controls/src/Core/Handlers/Items2/iOS/GroupableItemsViewController2.cs

@@ -127,7 +127,9 @@ void UpdateTemplatedSupplementaryView(TemplatedCell2 cell, NSString elementKind,
 
 			var bindingContext = ItemsSource.Group(indexPath);
 
+			cell.isHeaderOrFooterChanged = true;
 			cell.Bind(template, bindingContext, ItemsView);
+			cell.isHeaderOrFooterChanged = false;
 
 			// if (cell is ItemsViewCell2)
 			// {

src/Controls/src/Core/Handlers/Items2/iOS/StructuredItemsViewController2.cs

@@ -106,6 +106,7 @@ void UpdateDefaultSupplementaryView(DefaultCell2 cell, NSString elementKind)
 		void UpdateTemplatedSupplementaryView(TemplatedCell2 cell, NSString elementKind)
 		{
 			bool isHeader = elementKind == UICollectionElementKindSectionKey.Header;
+			cell.isHeaderOrFooterChanged = true;
 
 			if (isHeader)
 			{
@@ -131,6 +132,8 @@ void UpdateTemplatedSupplementaryView(TemplatedCell2 cell, NSString elementKind)
 				}
 				cell.Tag = FooterTag;
 			}
+
+			cell.isHeaderOrFooterChanged = false;
 		}
 
 		string DetermineViewReuseId(DataTemplate template, object item)

src/Controls/src/Core/Handlers/Items2/iOS/TemplatedCell2.cs

@@ -42,6 +42,9 @@ public event EventHandler<LayoutAttributesChangedEventArgs2> LayoutAttributesCha
 
 		internal bool MeasureInvalidated => _measureInvalidated;
 
+		// Flags changes confined to the header/footer, preventing unnecessary recycling and revalidation of templated cells.
+		internal bool isHeaderOrFooterChanged = false;
+
 		public DataTemplate CurrentTemplate
 		{
 			get => _currentTemplate is not null && _currentTemplate.TryGetTarget(out var target) ? target : null;
@@ -144,8 +147,16 @@ public override void PrepareForReuse()
 
 		public void Bind(DataTemplate template, object bindingContext, ItemsView itemsView)
 		{
-			var virtualView = PlatformHandler?.VirtualView as View ?? 
-			                  template.CreateContent(bindingContext, itemsView) as View;
+			View virtualView = null;
+			if (CurrentTemplate != template)
+			{
+				CurrentTemplate = template;
+				virtualView = template.CreateContent(bindingContext, itemsView) as View;
+			}
+			else if (PlatformHandler?.VirtualView is View existingView)
+			{
+				virtualView = existingView;
+			}
 
 			BindVirtualView(virtualView, bindingContext, itemsView, false);
 		}
@@ -157,6 +168,16 @@ public void Bind(View virtualView, ItemsView itemsView)
 
 		void BindVirtualView(View virtualView, object bindingContext, ItemsView itemsView, bool needsContainer)
 		{
+			var oldElement = PlatformHandler?.VirtualView as View;
+
+			if (oldElement is not null && oldElement != virtualView && isHeaderOrFooterChanged)
+			{
+				oldElement.BindingContext = null;
+				itemsView.RemoveLogicalChild(oldElement);
+				PlatformHandler = null;
+				PlatformView?.RemoveFromSuperview();
+			}
+
 			if (PlatformHandler is null && virtualView is not null)
 			{
 				var mauiContext = itemsView.FindMauiContext()!;