Touch Class

Provides an application-level service that processes multitouch input from the operating system and raises the FrameReported event.

System.Object
  System.Windows.Input.Touch

Namespace:  System.Windows.Input
Assembly:  PresentationCore (in PresentationCore.dll)

'Declaration
Public NotInheritable Class Touch

The Touch type exposes the following members.

  NameDescription
Public eventStatic memberFrameReportedOccurs when a touch message is sent.
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The FrameReported event is included in Windows Presentation Foundation (WPF) to support compatibility with Silverlight. If you do not have to ensure compatibility with Silverlight, use the touch events, such as TouchDown and TouchMove, on UIElement, UIElement3D, or ContentElement.

The FrameReported event does not use the same event model as other WPF input events, such as TouchDown and TouchMove. Instead of being exposed as an element-specific event that potentially routes through the object tree of a UI, the FrameReported event is a single event that is handled at the application level. Therefore, you cannot use the sender parameter of the event handler to determine what element is touched.

Use the TouchFrameEventArgs to get the TouchPoint values that are relevant to the touch event. From the TouchPoint, you can get the Position of the touch and determine whether the TouchAction was a Down, Move, or Up action. You can also use the TouchPoint to get the TouchDevice. From the TouchDevice, you can determine the device Id and get information about the element that is touched.

The following example enables you to create simple patterns on a Canvas by dragging two fingers across a touchscreen. Each touch is represented by a TouchDevice.The pattern is created by drawing a line between the touch points 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.

<Window x:Class="WpfTouchFrameSample.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" />     
    </Grid>
</Window>

The following code handles the FrameReported event. When a touch presses on the Canvas, the TouchDevice is captured to the Canvas. When the touch is lifted, the TouchDevice is released. When a touch moves across 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.

Class MainWindow
    ' Variables for tracking the position of two points. 
    Private pt1, pt2 As Point

    Public Sub New()
        InitializeComponent()
        AddHandler Touch.FrameReported, AddressOf Touch_FrameReported
    End Sub 

    Private Sub Touch_FrameReported(ByVal sender As System.Object, ByVal e As System.Windows.Input.TouchFrameEventArgs)
        If (canvas1 IsNot Nothing) Then 
            For Each _touchPoint In e.GetTouchPoints(Me.canvas1)

                If _touchPoint.Action = TouchAction.Down Then 
                    ' Clear the canvas and capture the touch to it.
                    canvas1.Children.Clear()
                    _touchPoint.TouchDevice.Capture(canvas1)

                ElseIf _touchPoint.Action = TouchAction.Move Then 
                    ' This is the first (primary) touch point. Just record its position. 
                    If _touchPoint.TouchDevice.Id = e.GetPrimaryTouchPoint(Me.canvas1).TouchDevice.Id Then
                        pt1.X = _touchPoint.Position.X
                        pt1.Y = _touchPoint.Position.Y

                        ' This is not the first touch point; draw a line from the first point to this one. 
                    ElseIf _touchPoint.TouchDevice.Id <> e.GetPrimaryTouchPoint(Me.canvas1).TouchDevice.Id Then
                        pt2.X = _touchPoint.Position.X
                        pt2.Y = _touchPoint.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
                        Me.canvas1.Children.Add(_line)
                    End If 

                ElseIf _touchPoint.Action = TouchAction.Up Then 
                    ' If this touch is captured to the canvas, release it. 
                    If (_touchPoint.TouchDevice.Captured Is canvas1) Then
                        canvas1.ReleaseTouchCapture(_touchPoint.TouchDevice)
                    End If 
                End If 
            Next 
        End If 
    End Sub 
End Class

.NET Framework

Supported in: 4.5.2, 4.5.1, 4.5, 4

.NET Framework Client Profile

Supported in: 4

Windows 8.1, Windows Server 2012 R2, Windows 8, Windows Server 2012, Windows 7, Windows Vista SP2, Windows Server 2008 (Server Core Role not supported), Windows Server 2008 R2 (Server Core Role supported with SP1 or later; Itanium not supported)

The .NET Framework does not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.

Any public static (Shared in Visual Basic) members of this type are thread safe. Any instance members are not guaranteed to be thread safe.
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