KeyDown 事件不会从 UWP 中的选定网格触发

Question

I'm working on custom control like calendar, where I have a panel as month view in which Grid cells are arranged as Date cells. The grid has a content presenter with TextBlock as a content template. Everything working fine. Pointerpressed, pointerReleased and OnTapped override methods are working fine for Grid but OnKeyDown override method or KeyDown event doesn't trigger from it. I also tried with PreviewKeyDown. Please help me to overcome this issue.

Answer 1

KeyDown event doesn't trigger from selected grid in UWP

The problem is that the Grid was not focused, so the event will not be triggered as expect. The better way is that listen CoreWindow KeyDown event, because when the app is running in foreground, CoreWindow will be focused automatically.

Window.Current.CoreWindow.KeyDown += CoreWindow_KeyDown;
private void CoreWindow_KeyDown(Windows.UI.Core.CoreWindow sender, Windows.UI.Core.KeyEventArgs args)
{
   MyBlock.Text = args.VirtualKey.ToString();
}

Answer 2

The key down event only trigger from keyboard focused control. And the Grid is not a control and the Grid is Panel. In UWP, only the control can set focus.

You can write a empty control and add it to Grid to set the control focus.

class Foo : Control
{
    protected override void OnKeyDown(KeyRoutedEventArgs e)
    {
        Debug.WriteLine("Foo key down");
    }
}

    <Grid x:Name="Grid2" Margin="10,10,10,10" Width="100" Background="#565656" HorizontalAlignment="Right" 
          KeyDown="Grid2_OnKeyDown">
        <local:Foo x:Name="Foo"></local:Foo>
    </Grid>

You can write any code to help debug when the Grid2 key down.

    private void Grid2_OnKeyDown(object sender, KeyRoutedEventArgs e)
    {
        Debug.WriteLine("Grid2 key down");
    }

And then you can set the Foo property focus when the Grid2 clicked.

    private async void Grid2_OnPointerReleased(object sender, PointerRoutedEventArgs e)
    {
        await Dispatcher.RunAsync(CoreDispatcherPriority.Normal, () => { Foo.Focus(FocusState.Keyboard); });
    }

Try to run the code and you can see the output windows show the message when you click the Grid2 and press key.

But why I write the code in dispatcher, because I should make the Foo control get focus. And if I do not use dispatcher and the pointer focus will in Grid and not any UIElement focus keyboard.