[Android] Fix for incorrect scroll position when using ScrollTo with a header in CollectionView

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

@@ -425,9 +425,9 @@ protected virtual int DetermineTargetPosition(ScrollToRequestEventArgs args)
 			if (args.Mode == ScrollToMode.Position)
 			{
 				// Do not use `IGroupableItemsViewSource` since `UngroupedItemsSource` also implements that interface
-				if (ItemsViewAdapter.ItemsSource is UngroupedItemsSource)
+				if (ItemsViewAdapter.ItemsSource is UngroupedItemsSource ungroupedSource)
 				{
-					return args.Index;
+					return ungroupedSource.HasHeader ? args.Index + 1 : args.Index;
 				}
 				else if (ItemsViewAdapter.ItemsSource is IGroupableItemsViewSource groupItemSource)
 				{

src/Controls/tests/TestCases.HostApp/Issues/Issue18389.cs

@@ -0,0 +1,113 @@
+using System.Collections.ObjectModel;
+
+namespace Maui.Controls.Sample.Issues;
+
+[Issue(IssueTracker.Github, 18389, "Incorrect scroll position when scrolling to an item with header in CollectionView", PlatformAffected.Android)]
+public class Issue18389 : ContentPage
+{
+	ObservableCollection<string> _items;
+	CollectionView2 _collectionView;
+	public Issue18389()
+	{
+		GenerateItems();
+
+		Grid mainGrid = new Grid
+		{
+			Padding = new Thickness(20),
+			RowSpacing = 10,
+			RowDefinitions =
+			{
+				new RowDefinition { Height = GridLength.Auto },
+				new RowDefinition { Height = GridLength.Auto },
+				new RowDefinition { Height = GridLength.Auto },
+				new RowDefinition { Height = GridLength.Star }
+			}
+		};
+
+		Button scrollToIndexButton = new Button
+		{
+			AutomationId = "Issue18389_ScrollToBtn",
+			Text = "Click me to scroll to index Count - 1!"
+		};
+		scrollToIndexButton.Clicked += ScrollToLastItem;
+
+		Button removeHeaderButton = new Button
+		{
+			AutomationId = "Issue18389_RemoveHeaderBtn",
+			Text = "Remove Header"
+		};
+		removeHeaderButton.Clicked += RemoveHeader;
+
+		Button resetCollectionViewButton = new Button
+		{
+			AutomationId = "Issue18389_ResetBtn",
+			Text = "Reset CollectionView to 0,0"
+		};
+		resetCollectionViewButton.Clicked += ResetCollectionView;
+
+		mainGrid.Add(scrollToIndexButton, 0, 0);
+		mainGrid.Add(resetCollectionViewButton, 0, 1);
+		mainGrid.Add(removeHeaderButton, 0, 2);
+
+		_collectionView = new CollectionView2
+		{
+			ItemsSource = _items,
+			ItemTemplate = new DataTemplate(() =>
+			{
+				Label label = new Label
+				{
+					FontSize = 40
+				};
+				label.SetBinding(Label.TextProperty, ".");
+				label.SetBinding(Label.AutomationIdProperty, ".");
+
+				return label;
+			}),
+			Header = new Label
+			{
+				Text = "Header",
+				BackgroundColor = Colors.Black,
+				TextColor = Colors.White,
+				FontSize = 50,
+				FontFamily = "Bold"
+			},
+			Footer = new Label
+			{
+				Text = "Footer",
+				BackgroundColor = Colors.Black,
+				TextColor = Colors.White,
+				FontSize = 50,
+				FontFamily = "Bold"
+			},
+		};
+
+		mainGrid.Add(_collectionView, 0, 3);
+
+		Content = mainGrid;
+	}
+
+	void GenerateItems()
+	{
+		_items = new ObservableCollection<string>();
+
+		for (int i = 1; i <= 20; i++)
+		{
+			_items.Add($"Item {i}");
+		}
+	}
+
+	void ScrollToLastItem(object sender, EventArgs e)
+	{
+		_collectionView.ScrollTo(_items.Count - 1, -1, ScrollToPosition.End);
+	}
+
+	void RemoveHeader(object sender, EventArgs e)
+	{
+		_collectionView.Header = null;
+	}
+
+	void ResetCollectionView(object sender, EventArgs e)
+	{
+		_collectionView.ScrollTo(0);
+	}
+}

src/Controls/tests/TestCases.Shared.Tests/Tests/Issues/Issue18389.cs

@@ -0,0 +1,35 @@
+using NUnit.Framework;
+using UITest.Appium;
+using UITest.Core;
+
+namespace Microsoft.Maui.TestCases.Tests.Issues;
+
+public class Issue18389 : _IssuesUITest
+{
+	public Issue18389(TestDevice device) : base(device)
+	{
+	}
+
+	public override string Issue => "Incorrect scroll position when scrolling to an item with header in CollectionView";
+
+	[Test]
+	[Category(UITestCategories.CollectionView)]
+	public void VerifyScrollToIndexWithHeader()
+	{
+		App.WaitForElement("Issue18389_ScrollToBtn");
+		App.Tap("Issue18389_ScrollToBtn");
+
+		App.WaitForElement("Item 20");
+
+		App.WaitForElement("Issue18389_ResetBtn");
+		App.Tap("Issue18389_ResetBtn");
+
+		App.WaitForElement("Item 1");
+
+		App.WaitForElement("Issue18389_RemoveHeaderBtn");
+		App.Tap("Issue18389_RemoveHeaderBtn");
+
+		App.Tap("Issue18389_ScrollToBtn");
+		App.WaitForElement("Item 20");
+	}
+}