[ToDo][iOS] Back button re-navigates to Tasks page

[agneszitte]

When I nav to the Tasks page and then navigate back with the back button, it keeps re-navigating to the Tasks page:

Originally posted by @kazo0 in #745 (comment)

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The issue is happening for iOS only at the moment and was there before the single project migration

[agneszitte]

I am still able to reproduce this issue with latest Uno.Sdk 5.6.30
The current actual result seems worse than before:

todo-ios-issue.mp4

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Tested with:

• Templates/SDK: 5.6.30
• VS version: VS 2022 (64-bit) - Version 17.13.0
• VS VSIX: 5.6.26
• Platform: iOS
• OS: Windows

[kazo0]

@agneszitte this behavior for the iOS NavigationBar has been reported before and is currently being looked at by @rajamatt

This is interestingly the only time I've seen this happen using the Material styles of NavigationBar. The other similar issues were only reproducible using the default style from the base Uno.Toolkit.WinUI library (the "Fluent" one)

Toolkit issue: unoplatform/uno.toolkit.ui#1332

[rajamatt]

Just to add that the bug with the back button navigation described in this issue is only in the ToDo app and could be unrelated to #1332 in Toolkit.

However, it is true that the video provided in Agnes' most recent comment that showcases the navigation bug also contains the #1332 issue (where the Content of the NavBar is duplicated). To this point we were only able to reproduce the issue with the Fluent NavBar so knowing it was also happening with the Material NavBar in this specific app was cause for investigation.

Mystery solved

Well, it turns out the NavBar Content is also duplicated with Material in all apps! The peculiarity with the ToDo app is that the Navbar's Background is transparent:

<utu:NavigationBar Content="Title" Background="Transparent">

Normally we do not make the NavBar transparent, so we cannot see under it. This means that for both Fluent and Material styled NavBars the Content is being duplicated, we just can't see the duplicated title with Material because it is hidden behind.

Here you can clearly see the Content is duplicated in a new Material app with a transparent NavBar: