TouchDevice Class

Definition

Namespace:

System.Windows.Input

Assembly:

PresentationCore.dll

Represents a single touch input produced by a finger on a touchscreen.

public ref class TouchDevice abstract : System::Windows::Input::InputDevice, System::Windows::Input::IManipulator

public abstract class TouchDevice : System.Windows.Input.InputDevice, System.Windows.Input.IManipulator

type TouchDevice = class
    inherit InputDevice
    interface IManipulator

Public MustInherit Class TouchDevice
Inherits InputDevice
Implements IManipulator

Inheritance

Object

DispatcherObject

InputDevice

TouchDevice

Implements

IManipulator

Examples

The following example enables you to create simple patterns on a Canvas by dragging two fingers on a touchscreen. Each touch is represented by a TouchDevice in the TouchEventArgs. The pattern is created by drawing a line between the touch points that are provided by the touches. This example requires a Windows Touch-compatible screen.

The following markup creates the user interface, which consists of a Canvas that is centered in a grid, and attaches the event handlers for the touch events.

<Window x:Class="WpfTouchEventsSample.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        Title="MainWindow" Height="525" Width="525">
    <Grid>
        <Canvas x:Name="canvas1"
                Width="500" Height="500"
                Background="Black"
                TouchDown="canvas_TouchDown"
                TouchMove="canvas_TouchMove"
                TouchUp="canvas_TouchUp" />
    </Grid>
</Window>

The following code handles the touch events. When a touch is pressed on the Canvas, the TouchDevice is captured to the Canvas. When the touch is lifted, the TouchDevice is released. When a touch moves on the Canvas, the Id is checked. If the move came from the first touch, its location is recorded. If the move came from the second touch, a line is drawn from the position of the first touch to the position of the second touch.

using System.Windows;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Shapes;
using System.Windows.Controls;

namespace WpfTouchEventsSample
{
    /// <summary>
    /// Interaction logic for MainWindow.xaml
    /// </summary>
    public partial class MainWindow : Window
    {
        // Variables to track the first two touch points 
        // and the ID of the first touch point.
        private Point pt1, pt2 = new Point();
        private int firstTouchId = -1;

        public MainWindow()
        {
            InitializeComponent();
        }

        private void canvas_TouchDown(object sender, TouchEventArgs e)
        {
            Canvas _canvas = (Canvas)sender as Canvas;
            if (_canvas != null)
            {
                _canvas.Children.Clear();
                e.TouchDevice.Capture(_canvas);

                // Record the ID of the first touch point if it hasn't been recorded.
                if (firstTouchId == -1)
                    firstTouchId = e.TouchDevice.Id;
            }
        }

        private void canvas_TouchMove(object sender, TouchEventArgs e)
        {
            Canvas _canvas = (Canvas)sender as Canvas;
            if (_canvas != null)
            {
                TouchPoint tp = e.GetTouchPoint(_canvas);
                // This is the first touch point; just record its position.
                if (e.TouchDevice.Id == firstTouchId)
                {
                    pt1.X = tp.Position.X;
                    pt1.Y = tp.Position.Y;
                }
                // This is not the first touch point; draw a line from the first point to this one.
                else if (e.TouchDevice.Id != firstTouchId)
                {
                    pt2.X = tp.Position.X;
                    pt2.Y = tp.Position.Y;

                    Line _line = new Line();
                    _line.Stroke = new RadialGradientBrush(Colors.White, Colors.Black);
                    _line.X1 = pt1.X;
                    _line.X2 = pt2.X;
                    _line.Y1 = pt1.Y;
                    _line.Y2 = pt2.Y;

                    _line.StrokeThickness = 2;
                    _canvas.Children.Add(_line);
                }
            }
        }

        private void canvas_TouchUp(object sender, TouchEventArgs e)
        {
            Canvas _canvas = (Canvas)sender as Canvas;
            if (_canvas != null && e.TouchDevice.Captured == _canvas)
            {
                _canvas.ReleaseTouchCapture(e.TouchDevice);
            }
        }
    }
}

Class MainWindow
    ' Variables to track the first two touch points 
    ' and the ID of the first touch point.
    Private pt1, pt2 As Point
    Private firstTouchId As Integer = -1
    ' Touch Down
    Private Sub canvas_TouchDown(ByVal sender As System.Object, ByVal e As System.Windows.Input.TouchEventArgs)
        Dim _canvas As Canvas = CType(sender, Canvas)
        If (_canvas IsNot Nothing) Then
            _canvas.Children.Clear()
            e.TouchDevice.Capture(_canvas)

            ' Record the ID of the first touch point if it hasn't been recorded.
            If firstTouchId = -1 Then
                firstTouchId = e.TouchDevice.Id
            End If
        End If
    End Sub
    ' Touch Move
    Private Sub canvas_TouchMove(ByVal sender As System.Object, ByVal e As System.Windows.Input.TouchEventArgs)
        Dim _canvas As Canvas = CType(sender, Canvas)
        If (_canvas IsNot Nothing) Then
            Dim tp = e.GetTouchPoint(_canvas)
            ' This is the first touch point; just record its position.
            If e.TouchDevice.Id = firstTouchId Then
                pt1.X = tp.Position.X
                pt1.Y = tp.Position.Y

                ' This is not the first touch point; draw a line from the first point to this one.
            ElseIf e.TouchDevice.Id <> firstTouchId Then
                pt2.X = tp.Position.X
                pt2.Y = tp.Position.Y

                Dim _line As New Line()
                _line.Stroke = New RadialGradientBrush(Colors.White, Colors.Black)
                _line.X1 = pt1.X
                _line.X2 = pt2.X
                _line.Y1 = pt1.Y
                _line.Y2 = pt2.Y

                _line.StrokeThickness = 2
                _canvas.Children.Add(_line)
            End If
        End If
    End Sub
    ' Touch Up
    Private Sub canvas_TouchUp(ByVal sender As System.Object, ByVal e As System.Windows.Input.TouchEventArgs)
        Dim _canvas As Canvas = CType(sender, Canvas)
        If (_canvas IsNot Nothing AndAlso e.TouchDevice.Captured Is _canvas) Then
            _canvas.ReleaseTouchCapture(e.TouchDevice)

        End If
    End Sub
End Class

Remarks

You typically access a TouchDevice by using the TouchEventArgs.TouchDevice property. A TouchDevice represents a single touch on a screen. If multiple touches are present, use the Id property to distinguish between them.

Note

This class contains an inheritance demand at the class level that applies to all members. A SecurityException is thrown when the derived class does not have full-trust permission. For more information about security demands, see Link Demands and Inheritance Demands.

Constructors

TouchDevice(Int32)

Called from constructors in derived classes to initialize the TouchDevice class.

Properties

ActiveSource	Gets the PresentationSource that is reporting input for this device.
Captured	Gets the element that captured the TouchDevice.
CaptureMode	Gets the capture policy of the TouchDevice.
DirectlyOver	Gets the element that the touch contact point is directly over.
Dispatcher	Gets the Dispatcher this DispatcherObject is associated with. (Inherited from DispatcherObject)
Id	Gets the unique identifier of the TouchDevice, as provided by the operating system.
IsActive	Gets a value that indicates whether the device is active.
Target	Gets the element that receives input from the TouchDevice.

Methods

Activate()	Adds the TouchDevice to the input messaging system.
Capture(IInputElement, CaptureMode)	Captures a touch to the specified element by using the specified CaptureMode.
Capture(IInputElement)	Captures a touch to the specified element by using the Element capture mode.
CheckAccess()	Determines whether the calling thread has access to this DispatcherObject. (Inherited from DispatcherObject)
Deactivate()	Removes the TouchDevice from the input messaging system.
Equals(Object)	Determines whether the specified object is equal to the current object. (Inherited from Object)
GetHashCode()	Serves as the default hash function. (Inherited from Object)
GetIntermediateTouchPoints(IInputElement)	When overridden in a derived class, returns all touch points that are collected between the most recent and previous touch events.
GetTouchPoint(IInputElement)	Returns the current position of the touch device relative to the specified element.
GetType()	Gets the Type of the current instance. (Inherited from Object)
MemberwiseClone()	Creates a shallow copy of the current Object. (Inherited from Object)
OnCapture(IInputElement, CaptureMode)	Called when a touch is captured to an element.
OnManipulationEnded(Boolean)	Called when a manipulation has ended.
OnManipulationStarted()	Called when a manipulation is started.
ReportDown()	Reports that a touch is pressed on an element.
ReportMove()	Reports that a touch is moving across an element.
ReportUp()	Reports that a touch was lifted from an element.
SetActiveSource(PresentationSource)	Sets the PresentationSource that is reporting input for this device.
Synchronize()	Forces the TouchDevice to synchronize the user interface with underlying touch points.
ToString()	Returns a string that represents the current object. (Inherited from Object)
VerifyAccess()	Enforces that the calling thread has access to this DispatcherObject. (Inherited from DispatcherObject)

Events

Activated	Occurs when the TouchDevice is added to the input messaging system.
Deactivated	Occurs when the TouchDevice is removed from the input messaging system.
Updated	Occurs when a touch message is sent.

Explicit Interface Implementations

IManipulator.GetPosition(IInputElement)	Returns the position of the IManipulator object.
IManipulator.Id	Gets the unique identifier of the TouchDevice as provided by the operating system.
IManipulator.ManipulationEnded(Boolean)	Occurs when a manipulation has ended.