[Android][NavigationBar] MainCommand icon fails to update when switching themes

[erikvilima]

Current behavior

When switching themes (light/dark) the icon set as MainCommand of a NavigationBar fails to update its color.

How to reproduce it (as minimally and precisely as possible)

UnoApp1.zip

1. Download and run (on android) the repro
2. Navigate to the Second Page
3. Press the ToggleSwitch to switch themes
4. Observe that the back button won't update its color

Nuget Package:
Uno.Sdk - 5.6.20
Uno.Toolkit.WinUI - 6.4.1

Affected platform(s):

• Android

IDE:

• Visual Studio 2022

Relevant plugins:

Anything else we need to know?

[rajamatt]

Seems like an AppBarButton issue because the icon switches themes accordingly after removing the explicit MainCommand.

Doesn't look like its caused by the changes in #1302 because adding back those lines doesn't fix it.

[rajamatt]

Indeed theme switching doesn't work on an explicit MainCommand even with toolkit 6.2.0-dev.35, which was 6 months ago. So might be something we never handled.

[rajamatt]

The AppBarButtonRenderer.Invalidate() is never invoked when switching themes. But other invalidate methods like NavigationBarPresenter.Invalidate() are invoked because of properties like NavigationBar.Background changing.

After switching themes, if I force the invalidate on the MainCommand/AppBarButton the theme of the AppBarButton still doesn't change. So I think the properties of the AppBarButton are never updated in the first place, or they are updated on the wrong element since the property listeners don't observe any changes.

[kazo0]

@rajamatt

This is because the AppBarButton instance is never actually realized in the visual tree for the MainCommand. Unlike the PrimaryCommands, we cannot actually place the MainCommand AppBarButton inside of the native navbar. So we are simply doing a one-time forwarding of the relevant properties to the Android Toolbar navigation item.

I'm not sure if there would be an easy way to fix this