[iOS] Support for KeepLastItemInView for CollectionView2 on iOS

[kubaflo]

Note

Are you waiting for the changes in this PR to be merged?
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!

Issues Fixed

Fixes #28716
Fixes #31085

Before	After
Screen.Recording.2025-04-01.at.01.17.56.mov	Screen.Recording.2025-04-01.at.01.15.22.mov

<Grid RowDefinitions="Auto, *">
    <Button Text="Add Item"
            Clicked="Button_Clicked"
            HorizontalOptions="Center"
            VerticalOptions="Center"/>
    <CollectionView ItemsUpdatingScrollMode="KeepLastItemInView"
                    Grid.Row="1"
                    x:Name="cv">
        <CollectionView.ItemTemplate>
            <DataTemplate>
                <Grid ColumnDefinitions="*,Auto">
                    <Label
                        Text="{Binding Text}"
                        HeightRequest="100"
                        VerticalOptions="Center"/>
                </Grid>
            </DataTemplate>
        </CollectionView.ItemTemplate>
    </CollectionView>
</Grid>

[dotnet-policy-service]

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

[Copilot]

Pull Request Overview

This PR implements KeepLastItemInView support for CollectionView on iOS to address scroll behavior when new items are added to the collection. The implementation ensures that when new items are added to a CollectionView, the scroll position automatically moves to keep the last item visible.

Key changes:

• Added ItemsUpdatingScrollMode property to ItemsLayout to track scroll behavior
• Modified layout factory methods to pass through the scroll mode configuration
• Implemented automatic scrolling to last item in CustomUICollectionViewCompositionalLayout

Reviewed Changes

Copilot reviewed 6 out of 6 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
src/Controls/src/Core/Items/ItemsLayout.cs	Adds internal ItemsUpdatingScrollMode property to track scroll behavior
src/Controls/src/Core/Handlers/Items2/iOS/LayoutFactory2.cs	Updates layout creation methods to accept and handle ItemsUpdatingScrollMode parameter
src/Controls/src/Core/Handlers/Items2/ItemsViewHandler2.iOS.cs	Maps ItemsUpdatingScrollMode from ItemsView to ItemsLayout
src/Controls/tests/TestCases.HostApp/Issues/Issue28716.xaml	Creates test UI with three CollectionViews demonstrating the feature
src/Controls/tests/TestCases.HostApp/Issues/Issue28716.xaml.cs	Implements code-behind with data binding and command for adding items
src/Controls/tests/TestCases.Shared.Tests/Tests/Issues/Issue28716.cs	Adds automated UI test to verify the functionality works correctly

[Copilot]

The issue number in the attribute (28720) does not match the filename (Issue28716). This should be 28716 to maintain consistency.

Suggested change

	[Issue(IssueTracker.Github, 28720, "Support for KeepLastItemInView for CV2", PlatformAffected.iOS)]
	[Issue(IssueTracker.Github, 28716, "Support for KeepLastItemInView for CV2", PlatformAffected.iOS)]

[Copilot]

The scroll position logic assumes left-to-right layout direction. For right-to-left languages or when FlowDirection is RightToLeft, scrolling to UICollectionViewScrollPosition.Right may not provide the expected behavior of showing the 'last' item from the user's perspective.

Suggested change

	collectionView.ScrollToItem(lastIndexPath, UICollectionViewScrollPosition.Right, true);
	// Adjust scroll position for RTL layouts
	var layoutDirection = collectionView.EffectiveUserInterfaceLayoutDirection;
	var scrollPosition = layoutDirection == UIUserInterfaceLayoutDirection.RightToLeft
	? UICollectionViewScrollPosition.Left
	: UICollectionViewScrollPosition.Right;
	collectionView.ScrollToItem(lastIndexPath, scrollPosition, true);

[jfversluis]

@kubaflo I think this might make sense?

[FlavioGoncalves-Cayas]

Looking forward to test this, but cannot get the artifacts when the build does not finish?

[kubaflo]

Looking forward to test this, but cannot get the artifacts when the build does not finish?

Yeah we need to trigger a build to generate artifacts. Luckily I know the best /azp triggerer @jfversluis who will do it for us 😄

[jfversluis]

/azp run MAUI-public

[azure-pipelines]

Azure Pipelines successfully started running 1 pipeline(s).

[jfversluis]

Beep boop 🤖

@FlavioGoncalves-Cayas let us know the results whenever the build finishes, thanks!

[FlavioGoncalves-Cayas]

There's not artifact produced when it fails like it did right?