[Android] Fixed CollectionView reordering last item

[vitalii-vov]

Description of Change

Fixed application crash when dragging an element to the end of a collection on Android.

Issues Fixed

Fixes #17823

[ghost]

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

[akhanalcs]

@vitalii-vov Can you add a unit test for this?

[vitalii-vov]

@rmarinho
Perhaps I didn’t understand something, but for some reason the tests on GitHub were not launched?
If you think this fix is not correct, you may want to undo it or run tests.
I also marked PullRequest as "Allow edits by maintainers" and you can change it if you see fit.
As I can see, issue #17823 is affecting many users and will continue to do so in the future. The essence of the problem is known - it is the index offset in the RecyclerView after adding a Header to it.

[jfversluis]

/azp run

[azure-pipelines]

Azure Pipelines successfully started running 3 pipeline(s).

[jsuarezruiz]

Could you share a sample where could reproduce the issue before the changes?. I would use it to validate in addition to update the PR adding an UI Test.

[vitalii-vov]

Hello,
Here is the HeaderTemplate Example #17825 (comment)

Another example is just add

<CollectionView.Header>
    <Label Text="Hello"/>
</CollectionView.Header>

to your CollectionView

[Domik234]

Hello,
will this be released for next SR? @jsuarezruiz , @rmarinho

The base of this fix is already visible on lines 36 and 41.

maui/src/Controls/src/Core/Handlers/Items/Android/Adapters/ReorderableItemsViewAdapter.cs

Line 36 in cc549b7

var fromItemIndex = fromIndex - (fromItemsSource?.HasHeader == true ? 1 : 0);

maui/src/Controls/src/Core/Handlers/Items/Android/Adapters/ReorderableItemsViewAdapter.cs

Line 41 in cc549b7

var toItemIndex = toIndex - (toItemsSource?.HasHeader == true ? 1 : 0);

Author just recreated fix used in the situation where "IsGrouped == true && Header != null" the same way for case where "IsGrouped = false && Header != null".

I've already tested this and I am currently using it in project the hard way (recreating classes and overriding methods).

This can solve application crashing for ppl using Header or HeaderTemplate and not using IsGrouped at the same time so from the base of logic this should be free fix even for testing.
Understandable could be request to make it work the same way as for the Grouped ones (using directly value from .HasHeader than from custom bool field) but holding this PR back just leaves unnecessary bug in code.

Video - Testing

PR17825-2.webm

Starts with No Fix
00:14 - Adding items to collection
00:18 -> 00:20 - Drag test - crashed
00:33 - Reapplying fix (based on @vitalii-vov )

Fixed
00:42 - Rebuilding application with fix
01:05 - Adding items to collection
01:09 -> 01:12 - Drag test - successful
01:14 -> 01:20 - Custom logic test (drag and drop based on item type)

Thanks,
Dominik Švarc

[rmarinho]

/rebase

[rmarinho]

We need to rebase, but also add a test for this issue.
@jfversluis do you know if we have any reorder test ?

[rmarinho]

/rebase

[rmarinho]

Needs rebase and add a test

[rmarinho]

/azp run

[azure-pipelines]

Azure Pipelines successfully started running 3 pipeline(s).

[rmarinho]

We should use HasHeader The adapter seems to have a one

ItemsViewAdapter.ItemsSource.HasHeader;