Polygon Keyboard Focus

Question

Can a polygon be assigned keyboard focus on a PointerPressed event?

I can get the pointer captured by the polygon

myPolygon.CapturePointer(e.Pointer);

but even so

myPolygon.Focus...

does not appear to be an option... 

 

Assuming the answer is no, I can't seem to get a Polygon KeyDown event to fire:

myPolygon.KeyDown += new KeyEventHandler(myPolygon_KeyDown);

is not invoked when pressing a key during pointer capture, presumably for lack of focus.

 

Alternatively I try to control the polygon indirectly via the parent canvas:

myCanvas.KeyDown += new  KeyEventHandler(myCanvas.KeyDown);

which works in SilverLight but again (here in Win Store App) pressing a key doesn't invoke the handler.

 

Previous posts would lead me to believe

Window.Current.CoreWindow.KeyDown += CoreWindow_KeyDown;

should work, but I don't know how to monitor the keydown events with this...

Is there a code example for implementing this strategy?  Or a brief explanation?

 

Thanks,,,

---

torpedo99

Answer 1

the Pointer events if for mouse not for keyboard. For catch the keyboard events you should look for keyUp event or KeyDown event, like you did.

Maybe this don´t raise, because don´t have focus, not? Try to subscribe that events in the page ...

---

Sara Silva
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Answer 2

An example:

<Page
    x:Class="App21.MainPage"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:local="using:App21"
    xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
    xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
    mc:Ignorable="d">
    <Grid Background="{StaticResource ApplicationPageBackgroundThemeBrush}">
        <Grid.RowDefinitions>
            <RowDefinition Height="*"/>
            <RowDefinition Height="*"/>
        </Grid.RowDefinitions>
        <Button Content="Go"/>
        <ContentControl Grid.Row="1" KeyDown="c_KeyDown_1" PointerPressed="c_PointerPressed_1">
            <Polygon Points="300,200 400,125 400,275 300,200" Stroke="Red" StrokeThickness="1">
                <Polygon.Fill>
                    <SolidColorBrush Color="Yellow"/>
                </Polygon.Fill>
            </Polygon>
        </ContentControl>
    </Grid>
</Page>

---

using System;
using Windows.UI.Xaml.Controls;
using Windows.UI.Xaml.Input;
namespace App21
{
    public sealed partial class MainPage : Page
    {
        public MainPage()
        {
            this.InitializeComponent();
        }
        private void c_KeyDown_1(object sender, KeyRoutedEventArgs e)
        {
            System.Diagnostics.Debug.WriteLine("c_KeyDown_1:{0}", DateTime.Now);
        }
        private void c_PointerPressed_1(object sender, PointerRoutedEventArgs e)
        {
            System.Diagnostics.Debug.WriteLine("c_PointerPressed_1:{0}", DateTime.Now);
            // ...
            ((Control)sender).Focus(Windows.UI.Xaml.FocusState.Programmatic);
            e.Handled = true; // compulsory
        }
    }
}

Note :

- "Can a polygon be assigned keyboard focus" : no.
- The concept consists in working with the 'Control' framework element in order to properly operate focus and keyboard. Neither Polygon/Shape nor Canvas/Panel inherit from Control.

Answer 3

Thanks for getting me on track.

This works:

<ContentControl KeyDown = "myKeyDown"/>

----> code behind:  key stroke in app window successfully invokes the event handler

But doesn't seem to work with a Canvas:

<Canvas KeyDown = "myKeyDown"/>

----> code behind:  key stroke in app window fails to invoke the event handler

If I am correct why is this?

---

torpedo99

Answer 4

Your scenario requires setting Focus. This operation is provided for framework elements of type 'Control', not for 'Canvas/Panel'.