Adds Shell Flyout Footer Template

[SkyeHoefling]

Description of Change

Adds the Shell Flyout Footer Template implementation for Android meeting the following specs documented in the issue:

[Spec]

• The footer should be fixed to the bottom of the flyout.
• The menu list should not go behind it and obscure the menu items.
• The footer should take any height.

Issues Resolved

• fix [Spec] Shell Flyout Footer Template #6292

API Changes

IShellController

Added:

View FlyoutFooter { get; }

Shell

Added:

View IShellController.FlyoutFooter { get; }
object FlyoutFooter { get; set; } // Bindable Property
DataTemplate FlyoutFooterTemplate { get; set; } // Bindable Property

There are several non-public methods added to this class, but the additions above are all the public changes that mirror FooterHeader

Platforms Affected

• Core/XAML (all platforms)
• Android

Behavioral/Visual Changes

Changed the ShellFlyoutTemplatedContentRenderer to render an additional ViewGroup that is the fixed FlyoutFooter which appears at the bottom of the Flyout.

FlyoutContent.axml

Added:

• FrameLayout which is used to add the content of `FlyoutFooter.

ShellFlyoutTemplatedContentRenderer

Modified:

• Updated the LoadView logic to properly insert the content from FlyoutFooter.
• Once the content is inserted the LoadView logic calculates the height of the footer and applies the margin to the RecyclerView. This change ensures the ShellContent and FlyoutItem does not get rendered behind the FlyoutFooter

Before/After Screenshots

This is a new feature so there is no before screenshot. The after screenshot is a gif demonstrating the new feature.

Testing Procedure

I updated the Xamarin.Forms.Sandbox project to use the new feature and completed my testing there.

• Created Header and Footer
• Added FlyoutItems and ShellContent
• Added many items to force the RecyclerView to scroll and demonstrated the items are not hidden behind the FlyoutFooter

PR Checklist

• Has automated tests
• Rebased on top of the target branch at time of PR
• Changes adhere to coding standard

Omitted Tests

There are currently no automated tests for this as the work focused on UI changes which can be difficult to write automation around. During the review process if we identify where tests are needed I am more than happy to add automated tests.

Questions

While working on this PR I noticed that ShellFlyoutContentRenderer didn't seem to be used and the
ShellFlyoutTemplatedContentRender render is used instead. Here is a code snippet that shows some stale code. I am not sure if this is a hold-over from an original attempt or needs to be removed or is there for a future implementation.

Xamarin.Forms/Xamarin.Forms.Platform.Android/Renderers/ShellRenderer.cs

Lines 166 to 170 in f0a33ee

	protected virtual IShellFlyoutContentRenderer CreateShellFlyoutContentRenderer()
	{
	return new ShellFlyoutTemplatedContentRenderer(this);
	//return new ShellFlyoutContentRenderer(this, AndroidContext);
	}

[PureWeen]

@ahoefling were you planning to work on the iOS side of this as well at all?

[SkyeHoefling]

I can, but I don't have a business need for iOS at the moment as my project is targeting Android and that is what I built this for. As of right now I am not planning to add an iOS portion for this PR unless it is required to move this PR forward.

I can certainly start looking at the iOS implementation sometime in the next week or so.

[PureWeen]

@ahoefling no worries on not working on iOS. I was only asking just so duplicate work didn't occur at all. This will get us to the Footer Templates a lot faster!! I have some work on ios I've been doing over here https://github.com/xamarin/Xamarin.Forms/tree/shell_fixes to smooth out the flyout so I'll probably just end up merging your work into that and then finishing up the footer on ios as well

We'll have to get an iOS implementation done before we can merge the Android one but this will get us there a lot faster!!

[SkyeHoefling]

@PureWeen I'm glad this is going to make the implementation much easier and we will be able to use the work I started here. How should we proceed with getting this merged into your shell_fixes branch? Should I be expecting comments in a code review here or will you be taking ownership of this when you are ready to merge it into your branch?

Curious on our process forward with this.

[paymicro]

LGTM

[PureWeen]

@ahoefling

will you be taking ownership of this when you are ready to merge it into your branch?

Once the work for this is top of the queue then we'll just take what you've done here and add onto it. Since you've already done a lot of the guts then we should be able to move this up in priority a bit faster.

I have a bunch of existing work I need to merge over on ios so I'm hoping I can take what you did here and easily provide a footer 🤞

[PureWeen]

@ahoefling Sorry about the delay but can you rebase this?
Let me know if you don't have time and I can take it over

[PureWeen]

/azp run

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[PureWeen]

/azp run

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