Navigation between pages

Once you have defined the pages for your application you need some way to display them. This can further be split into two scenarios,
  • For a set of standard pages (e.g. application home page, search page, ...) the Okra App Framework will automatically handle navigation at the appropriate times. All you need to do is name the page with one of the SpecialPageNames constants, and in some cases add the respective Okra service to your bootstrapper.
  • In other cases where you may want to programatically navigate from one page of you application to another - you do this using the INavigationContext and INavigationBase interfaces.

Navigating between pages with INavigationBase

The first step when you want to implement navigation from a page is to import a navigation manager implementing the INavigationBase interface. Since Okra supports multiple navigation contexts (e.g. main application, settings panes as well as more advanced navigation scenarios), you access the appropriate navigation manager via the INavigationContext.GetCurrent() method. For example you would add the following constructor to your view-model,

[ViewModelExport("MyPageName")]
public class MyViewModel : MyViewModelBase
{
    private readonly INavigationBase navigationManager;

    [ImportingConstructor]
    public MyViewModel(INavigationContext navigationContext)
    {
        this.navigationManager = navigationContext.GetCurrent();
    }
}

You can now use the methods on the INavigationBase instance to navigate between pages of your application. The Okra App Framework will manage the discovery, creation and navigation to the page specified in the NavigateTo(...) method (there are also extension methods to support using types for page names). For example,

public void NavigateToPage2()
{
    this.navigationManager.NavigateTo("Page 2");
}

And to return back through the navigation stack you simply call the GoBack() method. The Okra App Framework will handle storage, lifetime management and persistence of the navigation stack for you. For example,

public void NavigateBack()
{
    this.navigationManager.GoBack();
}

Programatically determining if you can navigate

When calling the NavigateTo(...) method it is anticipated that the specified page is defined with the appropriate attributes applied. If the page does not exist an exception is throw. Alternatively you can call the CanNavigateTo(...) method to return a boolean value representing whether the specified page exists.

Similarly there is a CanGoBack property and associated CanGoBackChanged event for determining whether the navigation manager will allow back navigation.

Last edited Apr 4, 2013 at 1:04 PM by AndyWilkinson, version 3

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