如何在 UWP 中处理 HardwareButtons.BackPressed？

Question

我有带 Prism 和 AppShell 的 UWP 应用程序。我想在通过 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;
        }
    }

但 rootFrame 始终为 null，如果历史堆栈为空并且我按下 BackButton 应用程序关闭，即使我这样做也是如此：

private void App_BackRequested(object sender, BackRequestedEventArgs e)
{
        e.Handled = true;
}

我也试过了

HardwareButtons.BackPressed += App_BackRequested;

也无济于事。

Answer 1

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();
            }
        }
    }

在 App.xaml.cs 的构造函数中添加这一行 -

HardwareButtons.BackPressed += HardwareButtons_BackPressed;

Answer 2

尝试将以下这些行添加到 OnLaunchApplicationAsync 方法

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();
            }
        };
        //......
     }

如何在 UWP 中处理 HardwareButtons.BackPressed？

How to handled HardwareButtons.BackPressed in UWP?

c#

xaml

prism

win-universal-app