Xamarin.Forms activate/deactivate toolbar items not working - xamarin.forms

Question

I have a Xamarin.Form MainPage:ContentPage with a ToolbarItems Bar on top. The toolbar items are bound to my ViewModel like so:
<ToolbarItem Text="Sync" Command="{Binding ReloadCommand}" >
</ToolbarItem>
The availability of the Item depends on some logic:
private bool canReloadExecute(object arg)
{
bool result = (!IsReloading && (App.GetPersistentSetting("DeviceID") != "") && (App.GetPersistentSetting("BuildingID") != ""));
return result;
}
There is a separate dialog controlling the DeviceID and BuildingID on a different settings page. Once any of those ids is entered it is persistently stored away
App.SetPersistentSetting("DeviceID",value);
Problem is, that the menu items don't change their appearance once my code uses popAsync() to return to the Main page. I need to restart my app to see the changes. According to the debugger, canReloadExecute isn't called. Why this?
What I tried to work around this issue is to force a refresh in the MainPage's OnAppearing method like this:
public void RefreshToolbarItems()
{
TestApp.ViewModels.MainViewModel mvm = (TestApp.ViewModels.MainViewModel)BindingContext;
mvm.RefreshToolbarItems();
}
... and in the ViewModel:
public void RefreshToolbarItems()
{
OnPropertyChanged("BuildingScanCommand");
OnPropertyChanged("ReloadCommand");
}
but this code runs through but changes nothing, while the Debugger shows that the routine is indeed firing the events, they seem to go nowhere.
Any ideas how I can get my menu going?
Edit 1: "Show command initalization"
I am not shre what specifically you mean, but here is the whole code dealing with the command:
private ICommand _reloadCommand;
public ICommand ReloadCommand => _reloadCommand ?? (_reloadCommand = new Command(ExecuteReloadCommand, canReloadExecute));
private bool _isReloading = false;
public bool IsReloading
{
get => _isReloading;
set
{
_isReloading = value;
((Command)_reloadCommand).ChangeCanExecute();
OnPropertyChanged(nameof(ReloadCommand));
}
}
private bool canReloadExecute(object arg)
{
bool result = (!IsReloading && (App.GetPersistentSetting("DeviceID") != "") && (App.GetPersistentSetting("BuildingID") != ""));
return result;
}
private async void ExecuteReloadCommand(object obj)
{
IsReloading = true;
// Some code ...
IsReloading = false;
}
The goal is to disable the command, if either the command handler is already running, or if the configuration of DeviceID and/or BuildingId hasn't been done yet.
The enable/disable does almost work, if I set the DeviceId and BuildingId, and restart the app, the command is properly enabled or disabled. It doesn't work, however, if I set the Ids in a sub-page and return to the main page.
meanwhile I came to the conclusion, that firing onPropertyChange obviously doesn't make the command check its canReloadExecute. So the question is, how do I trigger this?

Answer 1

I finally solved the issue myself, this code works nicely for me:
public void RefreshToolbarItems()
{
((Command)BuildingScanCommand).ChangeCanExecute();
((Command)ReloadCommand).ChangeCanExecute();
}