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UIElement.ManipulationDelta Event

 

Occurs when the input device changes position during a manipulation.

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

Public Event ManipulationDelta As EventHandler(Of ManipulationDeltaEventArgs)

The ManipulationDelta event occurs multiple times when the user drags fingers over the screen during a manipulation and again when inertia occurs. You can use the IsInertial property to check whether the event is occurring during inertia.

The element on with ManipulationDelta event occurs is not affected in any way when the event occurs. You must provide the logic to the element that is to be manipulated. The CumulativeManipulation and DeltaManipulation properties, which are of type ManipulationDelta, contain data about how the position of the manipulations change and interpreted as moving, resizing, or rotating an object. You apply that information to the element that is to be manipulated.

For more information about manipulations, see the Input Overview. For an example of an application that responds to manipulations, see Walkthrough: Creating Your First Touch Application.

The following example shows an event handler for the ManipulationDelta event. The example uses the DeltaManipulation property to move, resize, and rotate a Rectangle. The example also checks whether the ManipulationDelta event occurred during inertia and whether the rectangle is touching the edge of a window. If those cases are true, the application stops the manipulation to prevent the rectangle from leaving the visible area of the application. This example is part of a larger example in Walkthrough: Creating Your First Touch Application.

Private Sub Window_ManipulationDelta(ByVal sender As Object, ByVal e As ManipulationDeltaEventArgs)

    ' Get the Rectangle and its RenderTransform matrix.
    Dim rectToMove As Rectangle = e.OriginalSource
    Dim rectTransform As MatrixTransform = rectToMove.RenderTransform
    Dim rectsMatrix As Matrix = rectTransform.Matrix


    ' Rotate the shape
    rectsMatrix.RotateAt(e.DeltaManipulation.Rotation,
                         e.ManipulationOrigin.X,
                         e.ManipulationOrigin.Y)

    ' Resize the Rectangle. Keep it square 
    ' so use only the X value of Scale.
    rectsMatrix.ScaleAt(e.DeltaManipulation.Scale.X,
                        e.DeltaManipulation.Scale.X,
                        e.ManipulationOrigin.X,
                        e.ManipulationOrigin.Y)

    'move the center
    rectsMatrix.Translate(e.DeltaManipulation.Translation.X,
                          e.DeltaManipulation.Translation.Y)

    ' Apply the changes to the Rectangle.
    rectTransform = New MatrixTransform(rectsMatrix)
    rectToMove.RenderTransform = rectTransform

    Dim container As FrameworkElement = e.ManipulationContainer
    Dim containingRect As New Rect(container.RenderSize)

    Dim shapeBounds As Rect = rectTransform.TransformBounds(
                                New Rect(rectToMove.RenderSize))

    ' Check if the rectangle is completely in the window.
    ' If it is not and intertia is occuring, stop the manipulation.
    If e.IsInertial AndAlso Not containingRect.Contains(shapeBounds) Then
        e.Complete()
    End If

    e.Handled = True
End Sub

.NET Framework
Available since 4.0
Silverlight
Available since 4.0
Windows Phone Silverlight
Available since 7.0
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