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App navigation

❗ There is also a version of this document with code samples in C# ❗

NavigationService

The NavigationService is in charge of handling the navigation between app pages.

NavigationService has different implementations for the different supported design patterns.

  • Code Behind and MVVM Basic

    • NavigationService is defined as a static class that uses the Navigate method to navigate between pages and uses the target page type as a parameter.

  • MVVM Light

    • The ViewModelLocator creates the NavigationServiceEx instance and registers it with the SimpleIoC container. Each ViewModel and associated page must also be registered as navigation is done by passing the ViewModel name to the Navigate method.
Private _navigationService As NavigationServiceEx = New NavigationServiceEx()

Public Sub ViewModelLocator()
    ServiceLocator.SetLocatorProvider(Function() SimpleIoc.[Default])
    Register(Of HomeViewModel, HomePage)()
    SimpleIoc.[Default].Register(Function() _navigationService)
End Sub

Navigation initialization

App.xaml.vb creates the ActivationService and passes it the current App instance, the default navigation target, and, optionally, a UIElement to act as a navigation shell. If no shell is specified the current window content will be initialized as a Frame.

Normal launching of the app is passed by the ActivationService to the DefaultLaunchActivationHandler and this also sets the default page to display when launching the app.

Understanding navigation in each project type

Navigation differs between different project types.

  • Blank project type sets Window.Current.Content as a new Frame and navigates to the HomePage by default. NavigationService will do future navigation in this frame.
  • Navigation Pane project type sets Window.Current.Content as a new ShellPage instance. This ShellPage will set NavigationService frame to a frame within the page and NavigationService will do future navigation in this frame. You can find more on configuring code generated with this project type here.
  • Pivot and Tabs project type sets Window.Current.Content as a new Frame and navigates to PivotPage that contains a PivotControl, this PivotControl contains one PivotItem for each page. PivotItems contains header text and a Frame set display the configured page. With this project type, the NavigationService does not manage navigating between pivot items, but could be used to navigate away from the PivotPage if necessary.

Mixed navigation sample

This sample is based on Windows Template Studio 1.3 release and shows an app which includes a startup page that is displayed before navigating to a shell page and then behaving like a Navigation Pane project. The following code uses MVVM Basic, versions for MVVM Light and Code Behind are also available.

  • Step 1. Navigate to the Start Page

In App.xaml.vb the ActivationService has been changed to start on the new page.

Private Function CreateActivationService() As ActivationService
    ' This is the default navigation for a NavigationPane project type
    ' return new ActivationService(this, typeof(Views.HomePage), new Views.ShellPage());

    ' We are going to initialize navigation to a StartPage
    Return New ActivationService(Me, GetType(Views.StartPage))
End Function
  • Step 2. Return to normal Navigation Pane navigation.

Navigate to the ShellPage and this will reset the NavigationService Frame to it's own custom Frame. Then navigate to HomePage so something is displayed in the shell. All subsequent navigation just requires a single Navigate() call.

Public Class StartViewModel
    Inherits Observable

    Public Property StartCommand As ICommand

    Public Sub New()
        StartCommand = New RelayCommand(AddressOf OnStart)
    End Sub

    Private Sub OnStart()
        ' Navigating to a ShellPage, this will replaces NavigationService frame for an inner frame to change navigation handling.
        NavigationService.Navigate(Of Views.ShellPage)()

        ' Navigating now to a HomePage, this will be the first navigation on a NavigationPane menu
        NavigationService.Navigate(Of Views.HomePage)()
    End Sub
End Class

The three pages in this sample and the order in which they can be navigated to are shown below.

Mixed navigation sample

Learn more