public async override Task Activate(INavigationService navigationService, NavigationContextBase navigationContext, IReadOnlyDictionary<string, object> pageState)
{
await base.Activate(navigationService, navigationContext, pageState);
MyNavigationContext context = navigationContext as MyNavigationContext;
if (pageState != null)
{
/*********************************************************
* If you store state on deactivation and it is provided
* here, you know that the user has used the back button
* or returned from app suspension and should restore state.
*********************************************************/
this.Value1 = pageState[nameof(this.Value1)] as string;
this.Value2 = pageState[nameof(this.Value2)] as string;
this.Value3 = pageState[nameof(this.Value3)] as string;
}
else if (context != null)
{
/*********************************************************
* Alternatively, if the user has navigated to the page
* for the first time, there won't be existing page state
* to restore. The context can be used to populate the page.
*********************************************************/
this.Value1 = context.Value1;
this.Value2 = context.Value2;
this.Value3 = context.Value3;
}
}
/// <summary>
/// Adds a navigation context for storage.
/// </summary>
/// <param name="context">The context to be stored.</param>
/// <returns>The ID of the context for later retrieval.</returns>
public long Add(NavigationContextBase context)
{
if (context == null)
{
throw new ArgumentNullException("context");
}
long id = this.CurrentId;
this.contextStore.Add(id, context);
return id;
}
public async override Task Activate(INavigationService navigationService, NavigationContextBase navigationContext, IReadOnlyDictionary<string, object> pageState)
{
await base.Activate(navigationService, navigationContext, pageState);
MyNavigationContext context = navigationContext as MyNavigationContext;
if (pageState != null)
{
this.Value1 = pageState[nameof(this.Value1)] as string;
this.Value2 = pageState[nameof(this.Value2)] as string;
this.Value3 = pageState[nameof(this.Value3)] as string;
}
else if (context != null)
{
this.Value1 = context.Value1;
this.Value2 = context.Value2;
this.Value3 = context.Value3;
}
}
/// <summary>
/// Navigate to the specified page with the provided context.
/// </summary>
/// <param name="pageType">The type of page to navigate to.</param>
/// <param name="context">The context that should be provided to the page after navigation.</param>
public void Navigate(Type pageType, NavigationContextBase context = null)
{
if (pageType == null)
{
throw new ArgumentNullException(nameof(pageType));
}
if (context != null && !SuspensionManager.KnownTypes.Contains(context.GetType()))
{
throw new ArgumentException(
"Cannot navigate with a context that has not been registered as a Known Type. Use NavigationService.AddKnownTypes to register this context type before use.",
"context");
}
object parameter = null;
if (context != null)
{
parameter = this.contextService.Add(context);
}
this.RootFrame.Navigate(pageType, parameter);
}
/// <summary>
/// Creates a new NavigationService for a Frame, registering the frame and NavigationService
/// for future retrieval and registering the frame with the NavigationContextService.
/// </summary>
/// <param name="frame">The frame to register.</param>
/// <param name="defaultPage">The default page to navigate to if there is no state to restore.</param>
/// <param name="defaultNavigationContext">The navigation context to provide on navigation to defaultPage.</param>
/// <param name="restoreState">True to attempt to restore previously saved state, false to just navigate to defaultPage
/// without attempting to restore state.</param>
/// <returns>The NavigationService for the registered frame.</returns>
public static INavigationService RegisterFrame(Frame frame, Type defaultPage, NavigationContextBase defaultNavigationContext = null, bool restoreState = true)
{
if (frame == null)
{
throw new ArgumentNullException(nameof(frame));
}
if (defaultPage == null)
{
throw new ArgumentNullException(nameof(defaultPage));
}
if (GetNavigationService(frame) != null)
{
throw new InvalidOperationException("Frame already associated with a NavigationService.");
}
// Clean up references before adding a new one.
RemoveFrame();
NavigationService navigationService = new NavigationService(frame, new NavigationContextService());
// Ensure navigationService is fully registered before restoring state
// or navigating so that it can be accessed by PageBase.
NavigationServices.Add(navigationService);
if (restoreState)
{
// This triggers NavigatedTo on PageBase if there is state restored.
navigationService.RestoreState();
}
// If state wasn't restored, navigate to a default page to populate the Frame.
if (navigationService.RootFrame.Content == null)
{
navigationService.Navigate(defaultPage, defaultNavigationContext);
}
return navigationService;
}
