SplitView和后退按钮导航-UWP-C＃

Question

I am currently learning C# in UWP environment. I have a test app which is having a bit of the problem as described in Splitview with frame and navigating to another page, back button does not work .
But the my code is a little different from the above page.

My App.xaml.cs has the following code:

namespace Testing
{
/// <summary>
/// Provides application-specific behavior to supplement the default Application class.
/// </summary>
sealed partial class App : Application
{
    /// <summary>
    /// Initializes the singleton application object.  This is the first line of authored code
    /// executed, and as such is the logical equivalent of main() or WinMain().
    /// </summary>
    public App()
    {
        this.InitializeComponent();
        this.Suspending += OnSuspending;
        //NavigationCacheMode.Enabled;
    }

    /// <summary>
    /// Invoked when the application is launched normally by the end user.  Other entry points
    /// will be used such as when the application is launched to open a specific file.
    /// </summary>
    /// <param name="e">Details about the launch request and process.</param>
    protected override void OnLaunched(LaunchActivatedEventArgs e)
    {
#if DEBUG
        if (System.Diagnostics.Debugger.IsAttached)
        {
            this.DebugSettings.EnableFrameRateCounter = true;
        }
#endif
        Frame rootFrame = Window.Current.Content as Frame;

        // Do not repeat app initialization when the Window already has content,
        // just ensure that the window is active
        if (rootFrame == null)
        {
            // Create a Frame to act as the navigation context and navigate to the first page
            rootFrame = new Frame();

            rootFrame.NavigationFailed += OnNavigationFailed;

            if (e.PreviousExecutionState == ApplicationExecutionState.Terminated)
            {
                //TODO: Load state from previously suspended application
            }



            // Place the frame in the current Window
//--------------------------------------------------------------------
            //Window.Current.Content = new SplitShellPage(rootFrame);
//--------------------------------------------------------------------
            Window.Current.Content = rootFrame;
        }
        if (e.PrelaunchActivated == false)
        {
            if (rootFrame.Content == null)
            {
                // When the navigation stack isn't restored navigate to the first page,
                // configuring the new page by passing required information as a navigation
                // parameter
                rootFrame.Navigate(typeof(MainPage), e.Arguments);
            }

            Windows.UI.Core.SystemNavigationManager.GetForCurrentView().BackRequested += App_BackRequested;

            // Ensure the current window is active
            Window.Current.Activate();
        }
    }

    /// <summary>
    /// Invoked when Navigation to a certain page fails
    /// </summary>
    /// <param name="sender">The Frame which failed navigation</param>
    /// <param name="e">Details about the navigation failure</param>
    void OnNavigationFailed(object sender, NavigationFailedEventArgs e)
    {
        throw new Exception("Failed to load Page " + e.SourcePageType.FullName);
    }

    /// <summary>
    /// Invoked when application execution is being suspended.  Application state is saved
    /// without knowing whether the application will be terminated or resumed with the contents
    /// of memory still intact.
    /// </summary>
    /// <param name="sender">The source of the suspend request.</param>
    /// <param name="e">Details about the suspend request.</param>
    private void OnSuspending(object sender, SuspendingEventArgs e)
    {
        var deferral = e.SuspendingOperation.GetDeferral();
        //TODO: Save application state and stop any background activity
        deferral.Complete();
    }
    private void App_BackRequested(object sender, Windows.UI.Core.BackRequestedEventArgs e)
    {
        Frame rootFrame = Window.Current.Content as Frame;
        if (rootFrame == null)
            return;

        // Navigate back if possible, and if the event has not 
        // already been handled .
        if (rootFrame.CanGoBack && e.Handled == false)
        {
            e.Handled = true;
            rootFrame.GoBack();
        }
    }


}

}

If I use Window.Current.Content = new SplitShellPage(rootFrame); as in place of Window.Current.Content = rootFrame; the SplitView works but the back button does not work. If I use the second line then SplitView doesn't work but back navigation works.

I even tried setting my launch page to SplitView page as rootFrame.Navigate(typeof(SplitShellPage), e.Arguments); but that causes the application to stop at runtime and the application doesn't start.

The other pages with code are as:

SplitShellPage.xaml.cs

namespace Testing.Pages
{
/// <summary>
/// An empty page that can be used on its own or navigated to within a Frame.
/// </summary>
public sealed partial class SplitShellPage : Page
 {

    public SplitShellPage(Frame frame)
    {
        this.InitializeComponent();
        NavigationCacheMode = NavigationCacheMode.Enabled;
        shell_splitview.Content = frame;
        (shell_splitview.Content as Frame).Navigate(typeof(MainPage));
    }

    private void hamburger_btn_Click(object sender, RoutedEventArgs e)
    {
        shell_splitview.IsPaneOpen = !shell_splitview.IsPaneOpen;
    }
 }
}

This method of work I found when searching on google to make the NavigationPane work in all the pages and it does work in all the pages just without the Back Navigation .

MainPage.xaml.cs

namespace Testing
{
/// <summary>
/// An empty page that can be used on its own or navigated to within a Frame.
/// </summary>
public sealed partial class MainPage : Page
 {
    public MainPage()
    {
        this.InitializeComponent();
        NavigationCacheMode = NavigationCacheMode.Enabled;
    }


    private void Settings_Flyout_Click(object sender, RoutedEventArgs e)
    {
        this.Frame.Navigate(typeof(SettingsPage));
    }
 }
}

I have done some searches on google but nothing makes sense because they use some other methods and things get more complicated. Please let me know what I am doing wrong here and how to make it right. Thanks.
PS Let me know if I need to also share the XAML files.

Answer 1

If I use Window.Current.Content = new SplitShellPage(rootFrame); as in place of Window.Current.Content = rootFrame; the SplitView works but the back button does not work

In this situation, the frame currently you are using is shell_splitview.Content . Because you are using this code for navigating (shell_splitview.Content as Frame).Navigate(typeof(MainPage)); . So in App.xaml.cs the method App_BackRequested method try to get the Window.Current.Content as Frame for navigating, the back button will not work.

The solution is provided by the demo in the thread you reference, to add the BackRequested event handle in the page which defined the SplitView. Update your code in SplitShellPage.xaml.cs as follows the back button will work.

public SplitShellPage(Frame frame)
{
    this.InitializeComponent();
    NavigationCacheMode = NavigationCacheMode.Enabled;
    shell_splitview.Content = frame;
    (shell_splitview.Content as Frame).Navigate(typeof(MainPage));
    SystemNavigationManager.GetForCurrentView().BackRequested += SplitShellPage_BackRequested;
}

private void SplitShellPage_BackRequested(object sender, BackRequestedEventArgs e)
{
    Frame myFrame = shell_splitview.Content as Frame;
    if (myFrame.CanGoBack)
    {
        e.Handled = true;
        myFrame.GoBack();
    }
}

If I use the second line then SplitView doesn't work but back navigation works.

In this situation, we even did not access the SplitShellPage , and didn't access the SplitView . It is just a implemention of back button between two simple page. It works and has noting relationship with the content of SplitView .

The key point for this issue is to clear which frame you are using for navigating now , rootFrame( Window.Current.Content ) or the SplitViewContent frame. And navigating back with back button need the same frame.

You can download the demo from the thread you referenced for further testing. And more details please reference Back button navigation .