How to check if any key was pressed (frontend only)

Question

i have designed a .xamlx file that is only meant as an overview. If any key is pressed, my NavigateBackCommand should be executed. Is there an event on a page/grid like "anyKeyPressed"? I must be in the .xamlx, because I can´t (am not allowed to) change something in the backend.

Something like:

<Grid.Behaviors>
       <behaviors:EventHandlerBehavior EventName="anyKeyPressed">
        <behaviors:InvokeCommandAction Command="{Binding NavigateBackCommand}" />
       </behaviors:EventHandlerBehavior>
</Grid.Behaviors>

Answer 1

Is there an event on a page/grid like "anyKeyPressed"?

Unfortunately, no. And for mobile platform (Android/iOS), there's no such event as "anyKeyPressed" especially for physical keyboard.

If not considered frontend only, you can achieve it on UWP:

1. Create an Inteface called IKeyboardListener in your Shared Project:

namespace Forms2
{
    public interface IKeyboardListener
    {
    }
}

2. Add this to your UWP's App.xaml.cs:

namespace Forms2.UWP
{
    sealed partial class App : Application, IKeyboardListener
    {
        ....
        protected override void OnLaunched(LaunchActivatedEventArgs e)
        {
           ....
           
           Windows.UI.Core.CoreWindow.GetForCurrentThread().KeyDown += HandleKeyDown;
        }

        public void HandleKeyDown(Windows.UI.Core.CoreWindow window, Windows.UI.Core.KeyEventArgs e)
        {
            MessagingCenter.Send<IKeyboardListener, string>(this, "KeyboardListener", e.VirtualKey.ToString());
        }

    }
}

3. Use this on the page you want to execute the return command:

namespace Forms2
{
    public partial class Page1 : ContentPage
    {
        public Page1()
        {
            InitializeComponent();

           MessagingCenter.Subscribe<IKeyboardListener, string>(this, "KeyboardListener", (sender, args) => {

               Debug.WriteLine(args);
                if (args!=null)
                {
                    Navigation.PopAsync();
                }

           });
        }
    }
}

If any key is pressed, you can return previous page.