[iOS & Mac] Fix for Incorrect ItemsViewScrolledEventArgs Values in CollectionView with Grouped Items by SyedAbdulAzeemSF4852 · Pull Request #34240 · dotnet/maui

SyedAbdulAzeemSF4852 · 2026-02-25T12:18:03Z

Note

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It would be very helpful if you could test the resulting artifacts from this PR and let us know in a comment if this change resolves your issue. Thank you!

Issue Details

When a CollectionView's IsGrouped property is set to true, the values of FirstVisibleItemIndex, CenterItemIndex, and LastVisibleItemIndex in the ItemsViewScrolledEventArgs passed to the Scrolled event handler are incorrect.

Root Cause

Visible items were sorted only by Row, which produced incorrect ordering when items from multiple sections were visible simultaneously.

Description of Change

iOS (ItemsViewDelegator.cs and ItemsViewDelegator2.cs)

Changed the sort from .OrderBy(x => x.Row) to .OrderBy(x => x.Section).ThenBy(x => x.Row) so that IndexPathsForVisibleItems is ordered correctly across section boundaries. The fix is applied to both the legacy handler (Items/) and the current handler (Items2/).

Issues Fixed

Fixes #17664

Validated the behaviour in the following platforms

Windows
Android
iOS
Mac

Android fix PR: #31437

Output

Before	After
iOS_Before.mov	iOS_After.mov

…ctionView

dotnet-policy-service · 2026-02-25T12:18:28Z

Hey there @@SyedAbdulAzeemSF4852! Thank you so much for your PR! Someone from the team will get assigned to your PR shortly and we'll get it reviewed.

sheiksyedm · 2026-02-26T12:45:17Z

/azp run maui-pr-uitests

azure-pipelines · 2026-02-26T12:45:28Z

Azure Pipelines successfully started running 1 pipeline(s).

Copilot

Pull request overview

Fixes incorrect ItemsViewScrolledEventArgs visible-item indices for grouped CollectionView on iOS/Mac by ensuring visible NSIndexPaths are ordered consistently across section boundaries, and adds a HostApp repro page + Appium UI test for issue #17664.

Changes:

iOS (legacy Items/) and iOS/MacCatalyst (current Items2/) delegators now sort visible NSIndexPaths by Section then Row.
Added HostApp issue page (Issue17664) that displays the “last visible item” text while scrolling grouped content.
Added an Appium UI test (Issue17664) validating the label updates after a programmatic scroll.

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 6 comments.

File	Description
src/Controls/src/Core/Handlers/Items2/iOS/ItemsViewDelegator2.cs	Updates visible index-path ordering for grouped sources (Items2 iOS/MacCatalyst handler).
src/Controls/src/Core/Handlers/Items/iOS/ItemsViewDelegator.cs	Updates visible index-path ordering for grouped sources (legacy iOS handler).
src/Controls/tests/TestCases.HostApp/Issues/Issue17664.cs	Adds repro page using grouped CollectionView + Scrolled handler output.
src/Controls/tests/TestCases.Shared.Tests/Tests/Issues/Issue17664.cs	Adds Appium UI regression test for the issue.

Copilot · 2026-02-26T12:50:23Z

src/Controls/src/Core/Handlers/Items2/iOS/ItemsViewDelegator2.cs

+			// Sort visible item index paths by section and then by row for consistent order in both grouped and ungrouped sources
+			var indexPathsForVisibleItems = collectionView.IndexPathsForVisibleItems.OrderBy(x => x.Section).ThenBy(x => x.Row).ToList();



GetVisibleItemsIndexPath now orders IndexPathsForVisibleItems by Section/Row, but GetCenteredIndexPath still orders only by Row. If IndexPathForItemAtPoint returns null (e.g., center point lands between cells/headers), the fallback uses the incorrectly-sorted "first" index path, which can still produce wrong CenterItemIndex for grouped sources. Update GetCenteredIndexPath to use the same Section/Row ordering for consistency.

Copilot · 2026-02-26T12:50:24Z

src/Controls/src/Core/Handlers/Items/iOS/ItemsViewDelegator.cs

+			// Sort visible item index paths by section and then by row for consistent order in both grouped and ungrouped sources
+			var indexPathsForVisibleItems = collectionView.IndexPathsForVisibleItems.OrderBy(x => x.Section).ThenBy(x => x.Row).ToList();



GetVisibleItemsIndexPath now orders IndexPathsForVisibleItems by Section/Row, but GetCenteredIndexPath still orders only by Row. If IndexPathForItemAtPoint returns null (e.g., center point lands between cells/headers), the fallback uses the incorrectly-sorted "first" index path, which can still produce wrong CenterItemIndex for grouped sources. Update GetCenteredIndexPath to use the same Section/Row ordering for consistency.

Copilot · 2026-02-26T12:50:24Z

src/Controls/tests/TestCases.Shared.Tests/Tests/Issues/Issue17664.cs

@@ -0,0 +1,31 @@
+#if TEST_FAILS_ON_ANDROID // PR Link - https://github.com/dotnet/maui/pull/31437


This test file is wrapped in #if TEST_FAILS_ON_ANDROID, which means it will never run in the Android UI test project (where TEST_FAILS_ON_ANDROID is not defined). If the intent is to validate the cross-platform fix (and especially if the linked Android fix has landed), remove this guard or switch to a runtime skip so Android gets regression coverage too.

Copilot · 2026-02-26T12:50:24Z

src/Controls/tests/TestCases.Shared.Tests/Tests/Issues/Issue17664.cs

+#if WINDOWS
+		Thread.Sleep(1000);
+#endif
+
+		var resultItem = App.WaitForElement("Issue17664DescriptionLabel").GetText();
+		Assert.That(resultItem, Is.EqualTo("Category C item #2"));


Avoid platform-specific #if WINDOWS + Thread.Sleep in the test body; it’s brittle and can still be flaky. Prefer waiting for the expected UI state (e.g., wait until the label text becomes the expected value using an existing wait helper) so the test is stable across platforms without conditional compilation.

Copilot · 2026-02-26T12:50:25Z

src/Controls/tests/TestCases.HostApp/Issues/Issue17664.cs

+		_collectionView.Scrolled += (s, e) =>
+		{
+			var flatItems = _groupedItems.SelectMany(group => group).ToList();
+			if (e.LastVisibleItemIndex < flatItems.Count)
+			{
+				descriptionLabel.Text = flatItems[e.LastVisibleItemIndex];
+			}
+		};


The Scrolled handler assumes LastVisibleItemIndex is always non-negative. On some platforms/conditions ItemsViewScrolledEventArgs can report -1, and the current check (< flatItems.Count) would still pass and then index flatItems[-1], causing an exception. Add a >= 0 guard (or otherwise handle -1) before indexing into flatItems.

Copilot · 2026-02-26T12:50:25Z

src/Controls/tests/TestCases.HostApp/Issues/Issue17664.cs

+
+namespace Maui.Controls.Sample.Issues;
+
+[Issue(IssueTracker.Github, 17664, "Incorrect ItemsViewScrolledEventArgs in CollectionView when IsGrouped is set to true", PlatformAffected.iOS | PlatformAffected.Android)]


The IssueAttribute marks this as affecting iOS/Android only, but this PR targets iOS + Mac as well. Consider adding PlatformAffected.macOS (and any other affected platforms) so the metadata matches where this scenario is expected to reproduce/be validated.

Suggested change

[Issue(IssueTracker.Github, 17664, "Incorrect ItemsViewScrolledEventArgs in CollectionView when IsGrouped is set to true", PlatformAffected.iOS | PlatformAffected.Android)]

[Issue(IssueTracker.Github, 17664, "Incorrect ItemsViewScrolledEventArgs in CollectionView when IsGrouped is set to true", PlatformAffected.iOS | PlatformAffected.Android | PlatformAffected.macOS)]

iOS: Fix incorrect ItemsViewScrolledEventArgs values in grouped Colle…

9e8dca6

…ctionView

dotnet-policy-service bot added the community ✨ Community Contribution label Feb 25, 2026

dotnet-policy-service bot added the partner/syncfusion Issues / PR's with Syncfusion collaboration label Feb 25, 2026

SyedAbdulAzeemSF4852 mentioned this pull request Feb 25, 2026

[Android] Fix for Incorrect ItemsViewScrolledEventArgs Values in CollectionView with Grouped Items #31437

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github-actions bot mentioned this pull request Feb 26, 2026

[repo-status] Daily Status Report - February 26, 2026 #34253

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sheiksyedm added area-controls-collectionview CollectionView, CarouselView, IndicatorView platform/ios labels Feb 26, 2026

sheiksyedm marked this pull request as ready for review February 26, 2026 12:44

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[iOS & Mac] Fix for Incorrect ItemsViewScrolledEventArgs Values in CollectionView with Grouped Items#34240

[iOS & Mac] Fix for Incorrect ItemsViewScrolledEventArgs Values in CollectionView with Grouped Items#34240
SyedAbdulAzeemSF4852 wants to merge 1 commit intodotnet:mainfrom
SyedAbdulAzeemSF4852:fix-17664_ios

SyedAbdulAzeemSF4852 commented Feb 25, 2026 •

edited by sheiksyedm

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		// Sort visible item index paths by section and then by row for consistent order in both grouped and ungrouped sources
		var indexPathsForVisibleItems = collectionView.IndexPathsForVisibleItems.OrderBy(x => x.Section).ThenBy(x => x.Row).ToList();

		@@ -0,0 +1,31 @@
		#if TEST_FAILS_ON_ANDROID // PR Link - https://github.com/dotnet/maui/pull/31437


		namespace Maui.Controls.Sample.Issues;

		[Issue(IssueTracker.Github, 17664, "Incorrect ItemsViewScrolledEventArgs in CollectionView when IsGrouped is set to true", PlatformAffected.iOS \| PlatformAffected.Android)]

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Issue Details

Root Cause

Description of Change

Issues Fixed

Validated the behaviour in the following platforms

Output

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SyedAbdulAzeemSF4852 commented Feb 25, 2026 •

edited by sheiksyedm

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