Shell navigation bar flickering during refresh (animation transition) after the menu/flyout item selection

[ivanzakharov]

Description

Out-of-the-box code sample with Shell navigation has a silly issue - when the flyout/menu item has been selected to jump to another content page, the navigation bar refreshes (or does the animation transition) completely with flickering and shows the white background for a fraction of a second.
It blocks us from using Shell for our Office-class business app.

Steps to Reproduce

1. Take ShellFlyoutSample from .NET MAUI Samples
2. Build it and run it on an Android emulator (Pixel 5, Android 13, API 33)
3. Switch between flyout items to see the flickering issue

Link to public reproduction project repository

https://github.com/dotnet/maui-samples

Version with bug

8.0.6

Is this a regression from previous behavior?

Not sure, did not test other versions

Last version that worked well

Unknown/Other

Affected platforms

Android, I was not able test on other platforms

Affected platform versions

Android 13

Did you find any workaround?

No, tried to fix it by adding Shell.PresentationMode="NotAnimated" (into AppShell.xaml, MainPage.xaml), but it didn't help

Recorded video with the animation transition issue:
https://github.com/dotnet/maui/assets/4208052/ea145382-e254-4143-b74e-bf6a726de7cd

Relevant log output

No response

[ivanzakharov]

Added another video that shows the issue with a white background underlying.
https://github.com/dotnet/maui/assets/4208052/cd9ddf35-ff69-4562-b2ee-42d6f2c466e5

BTW, the same white background appears in the dark theme.

[PureWeen]

Duplicate of #6389

Yea, unfortunately when Shell was originally implemented the second page gets pushed as a completely new coordinator layout with its own toolbar so you get a flash as the entire screen is swapped out (toolbar and everything). NavigationPage used to also do this in XF, but with MAUI we simplified it all down so there's now just a universal ToolBar for the entire app and you don't get any flickering. Ideally we can get shell pivoted to all the same backend code as NavigationPage which will fix this issue and make all our lives simpler.