[Android] Fixed CollectionView MeasureFirstItem ItemSizingStrategy Not Applied in Horizontal Layouts

[NanthiniMahalingam]

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!

Issue Details

• [Android] CollectionView MeasureFirstItem ItemSizingStrategy Not Applied in Horizontal Layouts.

Root Cause

• The first item's size was not applied correctly to subsequent items because the _pixelSize field was being set to null when using a horizontal orientation.

Description of Changes

• Removed the assignment of null to the _pixelSize field, ensuring the first item's size is preserved and used for measuring subsequent items.
• Introduced the UpdateAdapter method to re-measure and apply the first item’s size to all items when switching the layout orientation from vertical to horizontal.

Validated the behaviour in the following platforms

• Android
• Windows , iOS, MacOS - CollectionView MeasureFirstItem sizing not applied on Windows, iOS and macOS [[Windows & iOS] CollectionView2 ItemSizingStrategy="MeasureFirstItem" Fails to Apply Correct Sizing #29130]

Issues Fixed

Fixes #29192

Output images

Android

Before	After
Issue29192_Before.mov

[dotnet-policy-service]

Hey there @@NanthiniMahalingam! 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 pull request fixes an issue on Android where the CollectionView MeasureFirstItem sizing was not applied correctly in horizontal layouts. The changes ensure that the first item's size is preserved and correctly propagated, while also introducing an UpdateAdapter method to handle layout orientation changes.

• Removed an unnecessary assignment that reset the first item's pixel size.
• Updated the ItemsLayout mapping to call UpdateAdapter before updating the layout manager.
• Added test cases to validate the fix on multiple platforms (Android, Windows, iOS, macOS).

Reviewed Changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated no comments.

File	Description
src/Controls/tests/TestCases.Shared.Tests/Tests/Issues/Issue29192.cs	Added test case for verifying MeasureFirstItem sizing in CollectionView.
src/Controls/tests/TestCases.HostApp/Issues/Issue29192.cs	Introduced a sample ContentPage to test the horizontal layout behavior.
src/Controls/src/Core/Handlers/Items/StructuredItemsViewHandler.Android.cs	Updated MapItemsLayout to call UpdateAdapter, ensuring correct adapter updates.
src/Controls/src/Core/Handlers/Items/Android/ItemContentView.cs	Removed a duplicate assignment resetting _pixelSize to null.

[jsuarezruiz]

/azp run MAUI-UITests-public

[azure-pipelines]

Azure Pipelines successfully started running 1 pipeline(s).

[jsuarezruiz]

This test are failing, could verify if are related with the changes?

[NanthiniMahalingam]

This test are failing, could verify if are related with the changes?

Hi @jsuarezruiz ,

I've addressed the failing test case. Could you please verify it?

[jsuarezruiz]

/azp run MAUI-UITests-public

[azure-pipelines]

Azure Pipelines successfully started running 1 pipeline(s).

[jsuarezruiz]

/rebase

[jsuarezruiz]

/azp run

[azure-pipelines]

Azure Pipelines successfully started running 3 pipeline(s).