[ANDROID] ToolbarItem IsEnabled doesnt read initial binding, and doesnt behave like it should

[bentmar]

Description

ToolbarItems in a NavigationPage ignores the default value for a binding to the IsEnabled property.
On versions Before 4.X you have to force-set the default value on the UI-thread.
On versions 3.5.X and up it totally ignores the IsEnabled property.

Steps to Reproduce

1. Start The app
2. The default value for the IsEnabled binding is false
3. You can see that the initial behaviour is that the toolbarItem actually is enabled.
4. Uncomment the "MakeItWork" method and now it works.

Expected Behavior

If enabled is false either by changing the binding or reading the bindings initial value, the behaviour of the toolbaritem should be false too.

Actual Behavior

Initial value is not respected. Forcing the value to false (again) only works if you do it on UI thread.
On the later versions of XF IsEnabled is ignored.

Basic Information

On 4.X and 3.5.X changing isEnabled is totally ignored.

• Last known good version: 3.4.X (here the behaviour actullay changes, but fails
  to set initial value/behavior)

• IDE:
  Microsoft Visual Studio Enterprise 2017
  Version 15.9.7
  VisualStudio.15.Release/15.9.7+28307.423
  Microsoft .NET Framework
  Version 4.7.03190
  Installed Version: Enterprise
  Mono Debugging for Visual Studio 4.13.12-pre (9bc9548)
  Support for debugging Mono processes with Visual Studio.
  Xamarin 4.12.3.80 (d15-9@914127c74)
  Visual Studio extension to enable development for Xamarin.iOS and Xamarin.Android.
  Xamarin.Android SDK 9.1.7.0 (HEAD/ba9da7a76)
  Xamarin.Android Reference Assemblies and MSBuild support.

• Platform Target Frameworks:

  • Android: testes on 8.1 and 9.0

Reproduction Link

App2.zip

[jcmanke]

I believe this is because MenuItem.IsEnabledProperty was changed to a readonly BindableProperty in 3.5. Putting IsEnabled="False" in XAML rather than a binding throws an exception.

[samhouts]

That was done here: #4659 We'll have to investigate the implications. Thanks for the report!

[MagicAndre1981]

I also run into the IsEnabled issue with 3.6:

System.InvalidOperationException: The BindableProperty "IsEnabled" is readonly.

when using it in XAML.

[bentmar]

What does "Returned to backlog" mean? @samhouts

[MagicAndre1981]

@bentmar

https://en.wikipedia.org/wiki/Scrum_(software_development)#Product_backlog

[samhouts]

@bentmar We ran out of time in sprint 150. Sprint 151 and Sprint 152 theme is Shell stabilization, so it wasn't moved forward to those sprints. After this sprint, we'll be reassessing the backlog, including this item. Thanks!

[bentmar]

@MagicAndre1981 well yes..

Thanks for info @samhouts