Fixed Footer not displayed at the Bottom When EmptyView in CV2 (#28681)

* Fixed Footer not displayed at the Bottom When EmptyView in CV2

* Updated test sample with Background Color

* Updated fix for CV1

* Removed unwanted changes and updated screenshot

* Added comment in test sample

* Updated test sample

* Added snapshot for mac and WinUI

* Re- Added mac snapshot

* Update HeaderAndFooterShouldBeVisible.png

Author: Dhivya-SF4094

src/Controls/src/Core/Handlers/Items2/iOS/ItemsViewController2.cs

@@ -564,11 +564,11 @@ void TearDownEmptyView()
 			_emptyViewFormsElement = null;
 		}
 
-		void LayoutEmptyView()
+		virtual internal CGRect LayoutEmptyView()
 		{
 			if (!_initialized || _emptyUIView == null || _emptyUIView.Superview == null)
 			{
-				return;
+				return CGRect.Empty;
 			}
 
 			var frame = DetermineEmptyViewFrame();
@@ -577,6 +577,8 @@ void LayoutEmptyView()
 
 			if (_emptyViewFormsElement != null && ((IElementController)ItemsView).LogicalChildren.IndexOf(_emptyViewFormsElement) != -1)
 				_emptyViewFormsElement.Layout(frame.ToRectangle());
+
+			return frame;
 		}
 
 		internal protected virtual void UpdateVisibility()

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

@@ -101,6 +101,9 @@ void UpdateDefaultSupplementaryView(DefaultCell2 cell, NSString elementKind)
 				: ItemsView.Footer;
 
 			cell.Label.Text = obj?.ToString();
+			cell.Tag = elementKind == UICollectionElementKindSectionKey.Header
+				? HeaderTag
+				: FooterTag;
 		}
 
 		void UpdateTemplatedSupplementaryView(TemplatedCell2 cell, NSString elementKind)
@@ -157,6 +160,21 @@ string DetermineViewReuseId(DataTemplate template, object item)
 				? HorizontalSupplementaryView2.ReuseId
 				: VerticalSupplementaryView2.ReuseId;
 		}
+		internal override CGRect LayoutEmptyView()
+		{
+			var emptyViewFrame = base.LayoutEmptyView();
+			var footerView = CollectionView.ViewWithTag(FooterTag);
+
+			if (footerView is not null)
+			{
+				if (emptyViewFrame.Height > 0)
+					footerView.Frame = new CGRect(footerView.Frame.X, emptyViewFrame.Bottom, footerView.Frame.Width, footerView.Frame.Height);
+				else
+					footerView.Frame = new CGRect(footerView.Frame.X, CollectionView.ContentSize.Height - footerView.Frame.Height, footerView.Frame.Width, footerView.Frame.Height);
+			}
+
+			return emptyViewFrame;
+		}
 
 		protected override CGRect DetermineEmptyViewFrame()
 		{
@@ -172,8 +190,8 @@ protected override CGRect DetermineEmptyViewFrame()
 			if (footerView != null)
 				footerHeight = footerView.Frame.Height;
 
-			return new CGRect(CollectionView.Frame.X, CollectionView.Frame.Y, CollectionView.Frame.Width,
-				Math.Abs(CollectionView.Frame.Height - (headerHeight + footerHeight)));
+			return new CGRect(CollectionView.Frame.X, CollectionView.Frame.Y + headerHeight, CollectionView.Frame.Width,
+							Math.Abs(CollectionView.Frame.Height - (headerHeight + footerHeight)));
 		}
 
 		public override void ViewWillLayoutSubviews()

src/Controls/tests/TestCases.HostApp/Issues/Issue28604.cs

@@ -0,0 +1,61 @@
+using System.Collections.ObjectModel;
+
+namespace Maui.Controls.Sample.Issues;
+[Issue(IssueTracker.Github, 28604, "Footer Not Displayed at the Bottom When EmptyView is Active in CV2", PlatformAffected.iOS)]
+public class Issue28604 : ContentPage
+{
+    private CollectionViewViewModel ViewModel;
+
+    public Issue28604()
+    {
+        ViewModel = new CollectionViewViewModel();
+        BindingContext = ViewModel;
+
+        var grid = new Grid();
+
+        var collectionView = new CollectionView2
+        {
+            AutomationId = "CollectionView",
+            ItemsSource = ViewModel.ItemList,
+            EmptyView = "EmptyView",
+            Background = Colors.AliceBlue,
+            Header = new VerticalStackLayout
+            {
+                BackgroundColor = Colors.Red,
+                Children =
+                    {
+                        new Label
+                        {
+                            Text = "Header",
+                            FontAttributes = FontAttributes.Bold
+                        }
+                    }
+            },
+            Footer = new VerticalStackLayout
+            {
+                BackgroundColor = Colors.Yellow,
+                Children =
+                    {
+                        new Label
+                        {
+                            Text = "Footer",
+                            FontAttributes = FontAttributes.Bold
+                        }
+                    }
+            }
+        };
+        grid.Children.Add(collectionView);
+
+        Content = grid;
+    }
+}
+
+public class CollectionViewViewModel
+{
+    public ObservableCollection<string> ItemList { get; set; }
+
+    public CollectionViewViewModel()
+    {
+        ItemList = new ObservableCollection<string>();
+    }
+}

src/Controls/tests/TestCases.Mac.Tests/snapshots/mac/FooterShouldDisplayAtBottomOfEmptyView.png

@@ -0,0 +1,23 @@
+#if !ANDROID // this test case is ignored in android, as it has incositent scrolling behavior while using emptyView as string.  https://github.com/dotnet/maui/issues/28765 
+using NUnit.Framework;
+using UITest.Appium;
+using UITest.Core;
+
+namespace Microsoft.Maui.TestCases.Tests.Issues;
+
+public class Issue28604 : _IssuesUITest
+{
+    public Issue28604(TestDevice testDevice) : base(testDevice)
+    {
+    }
+    public override string Issue => "Footer Not Displayed at the Bottom When EmptyView is Active in CV2";
+
+    [Test]
+    [Category(UITestCategories.CollectionView)]
+    public void FooterShouldDisplayAtBottomOfEmptyView()
+    {
+        App.WaitForElement("CollectionView");
+        VerifyScreenshot();
+    }
+}
+#endif