Hit Testing on Windows Phone 8

Question

I would like to perform Hit Testing on Windows Phone. I found an article about it on MSDN but I am unable to reference HitResult class nor HitTest method.

This is the example link from MSDN and contained code:

// Respond to the left mouse button down event by initiating the hit test. 
private void OnMouseLeftButtonDown(object sender, MouseButtonEventArgs e)
{
    // Retrieve the coordinate of the mouse position.
    Point pt = e.GetPosition((UIElement)sender);

    // Perform the hit test against a given portion of the visual object tree.
    HitTestResult result = VisualTreeHelper.HitTest(myCanvas, pt);

    if (result != null)
    {
        // Perform action on hit visual object.
    }
}

Is there any easy and reliable pre-made way how to perform hit testing?

Update:

I need to work with Multi-touch that is why there is a timer approach with getting a collection of touch locations.

private void timer_Tick(object sender, EventArgs e)
        {
            TouchCollection touchCollection = TouchPanel.GetState();
            foreach (TouchLocation tl in touchCollection)
            {
                if ((tl.State == TouchLocationState.Pressed)
                        || (tl.State == TouchLocationState.Moved))
                {

                    // Get tapped element on the screen based on touch location.
                    // I am looking for the tapped rectangles that you can see in the XAML code.
                }
            }
        }

Part of XAML code:

<Grid x:Name="ContentPanel" Grid.Row="1" Margin="12,30,12,0">
            <Grid.Background>
                <ImageBrush Stretch="Fill"/>
            </Grid.Background>
            <Rectangle x:Name="tile11" HorizontalAlignment="Left" Height="103" Margin="10,22,0,0" VerticalAlignment="Top" Width="103" >
                <Rectangle.Fill>
                    <ImageBrush Stretch="Fill" ImageSource="/Assets/Tiles/DEFAULT.png"/>
                </Rectangle.Fill>
            </Rectangle>
            <Rectangle x:Name="tile12" HorizontalAlignment="Left" Height="103" Margin="120,22,0,0" VerticalAlignment="Top" Width="103" >
                <Rectangle.Fill>
                    <ImageBrush Stretch="Fill" ImageSource="/Assets/Tiles/DEFAULT.png"/>
                </Rectangle.Fill>
            </Rectangle>
// 

...

Answer 1

Unfortunately, HitTestResult etc. are not available on Windows Phone (there is a documentation bug that incorrectly associates all of .NET 4.5 with Windows Phone). You can use VisualTreeHelper to get at what you want though. You can handle a Tap event then use the coordinates to tell what control was tapped. For example:

private void OnTap(object sender, GestureEventArgs e)
{
    var element = (UIElement)sender;

    var controls = VisualTreeHelper.FindElementsInHostCoordinates(e.GetPosition(element), element);

    // TODO: something with controls, like search for type Button, etc.
}

Answer 2

You should probably use VisualTreeHelper.FindElementsInHostCoordinates, as the documentation for this method states (in Remarks):

FindElementsInHostCoordinates is fundamentally similar to the HitTest methods in other frameworks.

Answer 3

This is the solution to my problem:

private void timer_Tick(object sender, EventArgs e)
        {
            TouchCollection touchCollection = TouchPanel.GetState();
            var element = ContentPanel as UIElement;

            foreach (TouchLocation tl in touchCollection)
            {
                if ((tl.State == TouchLocationState.Pressed)
                        || (tl.State == TouchLocationState.Moved))
                {
                    var controls = VisualTreeHelper.FindElementsInHostCoordinates(new System.Windows.Point(tl.Position.X, tl.Position.Y), element);
                }
            }
        }