C# 如何处理UWP中的硬件按钮。反压？

我有UWP应用程序与棱镜和AppShell。 我希望在通过BackButton退出之前添加确认对话框。 我试过这个：

protected override Task OnLaunchApplicationAsync(LaunchActivatedEventArgs args)
    {
        ...
        SystemNavigationManager.GetForCurrentView().BackRequested += App_BackRequested;

        ...
    }

private void App_BackRequested(object sender, BackRequestedEventArgs e)
    {
        Frame rootFrame = Window.Current.Content as Frame;
        if (rootFrame == null)
        {  
           return;
        }

        if (rootFrame.CanGoBack && e.Handled == false)
        {
            <add confirm dialog here>
            e.Handled = true;
        }
    }

我也试过了

HardwareButtons.BackPressed += App_BackRequested;

---

这也没有帮助。

在App.xaml.cs中添加代码-

 private async void HardwareButtons_BackPressed(object sender, BackPressedEventArgs e)
    {

        e.Handled = true;
        Frame rootFrame = Window.Current.Content as Frame;
        if (rootFrame.CanGoBack && rootFrame != null)
        {

            rootFrame.GoBack();
        }
        else
        {
            var msg = new MessageDialog("Confirm Close");
            var okBtn = new UICommand("OK");
            var cancelBtn = new UICommand("Cancel");
            msg.Commands.Add(okBtn);
            msg.Commands.Add(cancelBtn);
            IUICommand result = await msg.ShowAsync();

            if (result != null && result.Label == "OK")
            {
                Application.Current.Exit();
            }
        }
    }

HardwareButtons.BackPressed += HardwareButtons_BackPressed;

在App.xaml.cs的构造函数中添加此行-

 private async void HardwareButtons_BackPressed(object sender, BackPressedEventArgs e)
    {

        e.Handled = true;
        Frame rootFrame = Window.Current.Content as Frame;
        if (rootFrame.CanGoBack && rootFrame != null)
        {

            rootFrame.GoBack();
        }
        else
        {
            var msg = new MessageDialog("Confirm Close");
            var okBtn = new UICommand("OK");
            var cancelBtn = new UICommand("Cancel");
            msg.Commands.Add(okBtn);
            msg.Commands.Add(cancelBtn);
            IUICommand result = await msg.ShowAsync();

            if (result != null && result.Label == "OK")
            {
                Application.Current.Exit();
            }
        }
    }

HardwareButtons.BackPressed += HardwareButtons_BackPressed;

---

尝试将以下几行添加到

OnLaunchApplicationAsync

方法中

protected override Task OnLaunchApplicationAsync(LaunchActivatedEventArgs args)
    {
        //......
        DeviceGestureService.GoBackRequested += (s, e) =>
        {
            e.Handled = true;
            e.Cancel = true;
            if (NavigationService.CanGoBack())
            {
                NavigationService.GoBack();
            }
            else
            {
                // PUT YOUR LOGIC HERE (Confirmation dialog before exit)
                Application.Current.Exit();
            }
        };
        //......
     }

---

它适用于新的空白项目，但不适用于我的应用程序。rootFrame始终为空，如果我在弹出窗口中按“否”，应用程序仍将关闭。我这样认为是因为我有这样一个：protectedoverride UIElement CreateShell（Frame-rootFrame）{var-shell=Container.Resolve（）；shell.SetContentFrame（rootFrame）；return-shell；}+1。如果您解释了您通过此实现的功能，PO将更容易理解您如何解决问题。使用Prism可以处理硬件按钮事件，如（CameraButtonReleased、CameraButtonPressed、CameraButtonHalfPressed、GoBackRequested等），只需在OnLaunchApplication异步方法中实现即可