Why do I get the default header at the top of my NavigationPage, when navigating to root in Xamarin.Forms with Prism?

Question

I have an iOS app written in Xamarin.Forms that uses the Prism NavigationService for navigation. When a user presses the Logout button, navigation returns to the Login Screen. After doing this more than once, the header reappears.

I have been suppressing the NavigationPage header on every screen with the code

NavigationPage.SetHasNavigationBar(this, false);

This works initially. However it stops working after popping off the navigation stack a few times.

On the login page where this occurs, I've also tried adding the following in XAML with the same result.

<ContentPage xmlns="http://xamarin.com/schemas/2014/forms" 
             xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml" 
             xmlns:local="clr-namespace:BIMSMobile.ViewModels"
             NavigationPage.HasNavigationBar="False"
             x:Class="BIMSMobile.Views.LoginPage">
    <ContentPage.Content>
...

I suppress the NavigationPage header in favor of a custom view that has the Logout button. The logout button has the following handler:

        protected void OnLogoutClicked(object sender, EventArgs e)
        {
                SessionHelper.Instance.SignOutUser();
        }

In the SessionHelper I do the following:

await NavigationService.NavigateAsync("NavigationPage/LoginPage");

The blue header is suppressed when the app is opened and is maintained for the first few back navigations (pop). I expect this to always be the case. However after the second time of logging out the default header reappears, push the rest of my content down on the screen.

Blanthor Blanthor · Accepted Answer · 2019-12-19T16:29:55

Apparently this was not caused by Navigation or by incorrectly calling SetHasNavigationBar in code. It was caused by styles in the resources :\ My fix is below.

       <Style TargetType="NavigationPage">
            <Setter Property="HasNavigationBar" Value="False" />
       </Style>

Why do I get the default header at the top of my NavigationPage, when navigating to root in Xamarin.Forms with Prism?

1 Answers