How can I override or act on KeyDown: Space or Enter for ListView in UWP?

Question

I've attached the KeyDown event to a ListView in my Win 10 UWP app. I want to make VirtualKey.Enter have a special effect, but the event is not firing for this particular key. Neither does it for Space, Arrow up or down. This I guess because the listview already has defined a special behaviour for those keys.

I'd like to override some of those keys though, or at least trigger additional actions. Even attaching events to those key with modifiers (e.g. Shift+ArrowDown) would not work because the events still are not firing.

I read that for WPF that there is a PreviewKeyDown-event which one can attach to. I can't find that event for UWP though. Are there any other options?

Knave

Are you genuinely interested in those keypresses, or do you want to modify the standard behavior, those keypresses trigger in the control? – Wow

I'm interested in the key presses. For space i want to invoke an action instead of deselect the item. For arrow left and right I also want to invoke an action – Knave

In these cases I usually attach the event on the parent control, then check if the focused control is which I'm looking for and then execute the desired logic. I don't know any other workaround for this on UWP. – Wivern

For info...PreviewKeyDown is now available in UWP – Alternate

Answer 1

Here is one way to do it : subscribe to the global Window.Current.CoreWindow.KeyDown event. Then save the focus state of your listview and react accordingly.

Here is the code :

public sealed partial class MainPage : Page
{
    bool hasFocus = false;
    public MainPage()
    {
        this.InitializeComponent();
        Window.Current.CoreWindow.KeyDown += CoreWindow_KeyDown;
    }

    private void CoreWindow_KeyDown(Windows.UI.Core.CoreWindow sender, Windows.UI.Core.KeyEventArgs args)
    {
        if(hasFocus)
        {
            Debug.Write("Key down on list");
        }
    }

    private void myList_GotFocus(object sender, RoutedEventArgs e)
    {
        hasFocus = true;

    }

    private void myList_LostFocus(object sender, RoutedEventArgs e)
    {
        hasFocus = false;
    }

You will also need to subscribe to the focus events in xaml, for your ListView :

<ListView .... GotFocus="myList_GotFocus" LostFocus="myList_LostFocus"/>

Hukill

Thanks! That solved the problem for Space, Up and Down, but Enter is still not firing. Any idea why? Not that it's a big issue, I can live without Enter. Maybe there are some other events triggering with Enter. – Knave

Note: Adding an event handler for a parent UI object the normal way as also suggested will not work since events are bubbled up, not down. I found this documentation that goes into detail and also describes how to work around it msdn.microsoft.com/en-us/windows/uwp/xaml-platform/… – Knave

@Stephanie It would be better to subscribe to the event in OnNavigatedTo or OnLoaded and of course remember to unsubscribe in OnNavigatedFrom – Steere

Answer 2

Stephanie's answer is a good one and it works in the general case. However, as Nilzor observed it will not work in the case of a ListView for the Enter key. For some reason the ListView handles the KeyDown event in case Enter is pressed.

A better way to handle key events when dealing with a ListView, as the question asks, is this.

 private void ListView_Loaded(object sender, RoutedEventArgs e)
    {
        (sender as ListView).AddHandler(UIElement.KeyDownEvent, new KeyEventHandler(ListView_KeyDown), true);
    }

 private void ListView_KeyDown(object sender, KeyRoutedEventArgs args)
    {
        if (args.Key == Windows.System.VirtualKey.Enter)
        {

        }
    }

Notice the last argument in the AddHandler function. This specifies whether we want to handle events already handled by a previous element in the visual tree. Of course don't forget to unsubscribe from the event when appropriate

Steere

Thank you so much for adding this answer! I completely forgot about this technique, and it solve my issue. I was trying to attach a KeyDown handler for a UWP Button to capture Enter and Space, and did not want to process them in a Click handler (which captures the Enter and Space keys automatically). This is definitely the right solution for this question. – Darius

Answer 3

Corcus's solution doesn't work for me. What is working is handling PreviewKeyDown directly from XAML. Works well for SPACE or ENTER key:

XAML:

<ListView PreviewKeyDown="BookmarksListView_PreviewKeyDown">

Code behind:

private void BookmarksListView_PreviewKeyDown(object sender, KeyRoutedEventArgs e)
{
    if (e.Key == Windows.System.VirtualKey.Enter)
    {
        // DO YOUR STUFF...
        e.Handled = true;
    }
}

Anarchic

Answer 4

You can use AddHandler method.

private void KeyEnterEventHandler(object sender, KeyRoutedEventArgs e)
    {
        if (e.OriginalKey == Windows.System.VirtualKey.Enter)
        {
            PlayFromListView();
        }
    }
    private void LoadListView()
    {
        foreach (var music in playListStorageFile.PlayList)
        {
            ListViewItem item = new ListViewItem();
            item.AddHandler(FrameworkElement.KeyDownEvent, new KeyEventHandler(KeyEnterEventHandler), true);

            TextBlock mytext = new TextBlock();
            mytext.Text = music.Nro.ToString() + " - " + music.Name;
            mytext.Tag = music.Nro;
            item.Content = mytext;
            lvMusics.Items.Add(item);
        }
    }

https://learn.microsoft.com/en-us/uwp/api/windows.ui.xaml.uielement.addhandler?view=winrt-18362

Ornithine