Handling the Touch.FrameReported Event

The following example shows how to change the color of a Border control by responding to the Touch.FrameReported event. Within the TouchPointView XAML file is a named Border control as shown:

Click here to view code image

<Grid x:Name="ContentPanel" Grid.Row="1" Margin="12,0,12,0">
    <Border x:Name="border"
        Height="100"
        Width="200"
        Background="{StaticResource PhoneAccentBrush}" />
</Grid>

The code-beside file, TouchPointView.xaml.cs, subscribes to the Touch.FrameReported event within the page constructor. The event handler retrieves the primary touch point, and if the TouchPoint is above the Border, the Border object’s Background is switched (see Listing 12.2).

LISTING 12.2. TouchPointView Class

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public partial class TouchPointView : PhoneApplicationPage
{
    readonly SolidColorBrush directlyOverBrush
                = new SolidColorBrush(Colors.Orange);
    readonly Brush normalBrush;

    public TouchPointView()
    {
        InitializeComponent();

        normalBrush = border.Background;

        Touch.FrameReported += HandleFrameReported;
    }

    void HandleFrameReported(object sender, TouchFrameEventArgs e)
    {
        TouchPoint primaryTouchPoint = e.GetPrimaryTouchPoint(null);

        if (primaryTouchPoint == null
            || primaryTouchPoint.TouchDevice.DirectlyOver != border)
        {
            return;
        }

        if (primaryTouchPoint.Action == TouchAction.Down)
        {            border.Background = directlyOverBrush;
        }
        else
        {
            border.Background = normalBrush;
        }
    }
}

Using the Touch and TouchPoint API provides you with the ability to respond to touch at a very low level. Subsequent sections of this chapter look at two higher-level abstractions of the Touch and TouchPoint APIs—namely, manipulation events and the Windows Phone Toolkit, beginning with manipulation events.