OnNavigatedTo is not called when using NavigationService.SelectTabAsync - xamarin.forms

Question

According to the documentation of Prism "when selecting a tab programmatically both the INavigationAware and IConfirmNavigation interfaces are invoked". But unfortunately this is not the case for me.
I did the following with Prism.DryIoc.Forms v7.2.0.1422 (also latest version did not work) and Xamarin.Forms v4.8.0.1560:
My MainPage:
<?xml version="1.0" encoding="utf-8" ?>
<TabbedPage
x:Class="SampleApp.Views.MainPage"
xmlns="http://xamarin.com/schemas/2014/forms"
xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
xmlns:prim="http://prismlibrary.com"
xmlns:views="clr-namespace:SampleApp.Views;assembly=SampleApp"
Title="{Binding Title}">
<NavigationPage Title="Page A">
<x:Arguments>
<views:APage Title="Page A" />
</x:Arguments>
<NavigationPage.Behaviors>
<prim:NavigationPageActiveAwareBehavior />
</NavigationPage.Behaviors>
</NavigationPage>
<NavigationPage Title="Page B">
<x:Arguments>
<views:BPage Title="Page B" />
</x:Arguments>
<NavigationPage.Behaviors>
<prim:NavigationPageActiveAwareBehavior />
</NavigationPage.Behaviors>
</NavigationPage>
<NavigationPage Title="Page C">
<x:Arguments>
<views:CPage Title="Page C" />
</x:Arguments>
<NavigationPage.Behaviors>
<prim:NavigationPageActiveAwareBehavior />
</NavigationPage.Behaviors>
</NavigationPage>
</TabbedPage>
In BPageViewModel selecting tab "APage" with NavigationParameters:
private async Task SayHelloOnPage()
{
var navParam = new NavigationParameters
{
{ "SayHelloTo", "Prism" }
};
await NavigationService.SelectTabAsync(nameof(APage), navParam);
}
In APageViewModel override OnNavigatedTo method:
public override void OnNavigatedTo(INavigationParameters parameters)
{
base.OnNavigatedTo(parameters);
System.Diagnostics.Debug.WriteLine($"OnNavigatedTo is called", nameof(APageViewModel));
if (parameters.ContainsKey("SayHelloTo"))
{
var name = parameters["SayHelloTo"] as string;
if (name != null)
{
System.Diagnostics.Debug.WriteLine($"Say Hello to {name}", nameof(APageViewModel));
}
}
}
See also this example project on my DropBox
Is this a bug or do I miss something?

Answer 1

I believe this is a bug, or at least an oversight in the API. It does call OnNavigatedTo, but only on the Page that is directly part of the TabbedPage. If you have your target page inside a NavigationPage, only the NavigationPage will get the OnNavigatedTo call. See https://github.com/PrismLibrary/Prism/blob/master/src/Forms/Prism.Forms/Navigation/TabbedPages/INavigationServiceExtensions.cs#L73-L74 .
I worked around this by copying the above implementation to my project and then changing the behaviour to instead call OnNavigatedTo on the relevant child page of the NavigationPage.