Touch.FrameReported Event

 

Occurs when a touch message is sent.

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

Public Shared Event FrameReported As TouchFrameEventHandler

A frame is one in a series of multitouch messages or touch points. You can respond to touches by handling the FrameReported event and accessing the details of the TouchPoint from the TouchFrameEventArgs event data.

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.

The following example 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.

This example is part of a larger example that is available in the Touch class overview.

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
Available since 4.0
Silverlight
Available since 3.0
Windows Phone Silverlight
Available since 7.0
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