Question

我目前正在UWP环境中学习C＃。我有一个测试应用程序，它有一些问题，如Splitview with frame and navigating to another page, back button does not work中所述但我的代码与上一页略有不同。

我的App.xaml.cs包含以下代码：

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();
        }
    }


}

}

如果我使用Window.Current.Content = new SplitShellPage(rootFrame);代替Window.Current.Content = rootFrame; SplitView，则后退按钮不起作用。如果我使用第二行，则SplitView无法正常工作，但返回导航工作。

我甚至尝试将我的启动页面设置为SplitView rootFrame.Navigate(typeof(SplitShellPage), e.Arguments);，但这会导致应用程序在运行时停止并且应用程序无法启动。

其他带代码的页面如下：

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;
    }
 }
}

我在谷歌搜索时发现的这种工作方法使NavigationPane在所有页面中都有效，并且在没有Back Navigation的所有页面中都能正常工作。

MainPage.xaml.cs中

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));
    }
 }
}

我在谷歌上做了一些搜索，但没有任何意义，因为他们使用其他一些方法，事情变得更复杂。请让我知道我在这里做错了什么以及如何做对。谢谢。
附：如果我还需要共享XAML个文件，请告诉我。

Answer 1

如果我使用Window.Current.Content = new SplitShellPage（rootFrame）;代替Window.Current.Content = rootFrame; SplitView有效，但后退按钮不起作用

在这种情况下，您当前使用的框架为shell_splitview.Content。因为您使用此代码来导航(shell_splitview.Content as Frame).Navigate(typeof(MainPage));。因此，在App.xaml.cs方法App_BackRequested方法尝试获取导航的Window.Current.Content as Frame，后退按钮将无效。

该解决方案由您引用的thread中的演示提供，用于在定义SplitView的页面中添加BackRequested事件句柄。更新SplitShellPage.xaml.cs中的代码，如下所示，后退按钮将起作用。

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();
    }
}

如果我使用第二行，那么SplitView不起作用，但返回导航工作。

在这种情况下，我们甚至没有访问SplitShellPage，也没有访问SplitView。它只是两个简单页面之间的后退按钮的实现。它起作用并且与SplitView的内容有关系。

此问题的关键点是清除您现在用于导航的帧，rootFrame（Window.Current.Content）或SplitViewContent帧。使用后退按钮导航需要相同的框架。

您可以从您引用的主题下载演示版以进行进一步测试。更多详情请参考Back button navigation。

SplitView和后退按钮导航 - UWP - C＃

1 个答案: