Silverlight 如何拖放对象

 

下面的示例演示如何在基于 Silverlight 的应用程序中拖放对象。出于安全考虑，不能在应用程序之间拖放对象。因此，说成在 Silverlight 插件区域内"滑动"对象更为准确。但是，术语"拖放"更为人知，因此在此处使用。

XAML

<UserControl x:Class="DragAndDropSimple.Page" xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" Width="400" Height="300"> <Canvas x:Name="rootCanvas" Width="640" Height="480" Background="Gray" > <!-- You can drag this rectangle around the canvas. --> <Rectangle MouseLeftButtonDown="Handle_MouseDown" MouseMove="Handle_MouseMove" MouseLeftButtonUp="Handle_MouseUp" Canvas.Left="30" Canvas.Top="30" Fill="Red" Width="50" Height="50" /> </Canvas> </UserControl>

C#

// Global variables used to keep track of the // mouse position and whether the object is captured // by the mouse. bool isMouseCaptured; double mouseVerticalPosition; double mouseHorizontalPosition; public void Handle_MouseDown (object sender, MouseEventArgs args) { Rectangle item = sender as Rectangle; mouseVerticalPosition = args.GetPosition(null).Y; mouseHorizontalPosition = args.GetPosition(null).X; isMouseCaptured = true; item.CaptureMouse(); } public void Handle_MouseMove(object sender, MouseEventArgs args) { Rectangle item = sender as Rectangle; if (isMouseCaptured) { // Calculate the current position of the object. double deltaV = args.GetPosition(null).Y - mouseVerticalPosition; double deltaH = args.GetPosition(null).X - mouseHorizontalPosition; double newTop = deltaV + (double)item.GetValue(Canvas.TopProperty); double newLeft = deltaH + (double)item.GetValue(Canvas.LeftProperty); // Set new position of object. item.SetValue(Canvas.TopProperty, newTop); item.SetValue(Canvas.LeftProperty, newLeft); // Update position global variables. mouseVerticalPosition = args.GetPosition(null).Y; mouseHorizontalPosition = args.GetPosition(null).X; } } public void Handle_MouseUp(object sender, MouseEventArgs args) { Rectangle item = sender as Rectangle; isMouseCaptured = false; item.ReleaseMouseCapture(); mouseVerticalPosition = -1; mouseHorizontalPosition = -1; }

Visual Basic

' Global variables used to keep track of the ' mouse position and whether the object is captured ' by the mouse. Dim isMouseCaptured As Boolean Dim mouseVerticalPosition As Double Dim mouseHorizontalPosition As Double Private Sub Handle_MouseDown(ByVal sender As Object, ByVal e As MouseButtonEventArgs) Dim item As Rectangle = sender mouseVerticalPosition = e.GetPosition(Nothing).Y mouseHorizontalPosition = e.GetPosition(Nothing).X isMouseCaptured = True item.CaptureMouse() End Sub Private Sub Handle_MouseMove(ByVal sender As Object, ByVal e As MouseEventArgs) Dim item As Rectangle = sender If (isMouseCaptured) Then ' Calculate the current position of the object. Dim deltaV As Double = e.GetPosition(Nothing).Y - mouseVerticalPosition Dim deltaH As Double = e.GetPosition(Nothing).X - mouseHorizontalPosition Dim newTop As Double = deltaV + item.GetValue(Canvas.TopProperty) Dim newLeft As Double = deltaH + item.GetValue(Canvas.LeftProperty) ' Set new position of object. item.SetValue(Canvas.TopProperty, newTop) item.SetValue(Canvas.LeftProperty, newLeft) ' Update position global variables. mouseVerticalPosition = e.GetPosition(Nothing).Y mouseHorizontalPosition = e.GetPosition(Nothing).X End If End Sub Private Sub Handle_MouseUp(ByVal sender As System.Object, ByVal e As System.Windows.Input.MouseButtonEventArgs) Dim item As Rectangle = sender isMouseCaptured = False item.ReleaseMouseCapture() mouseVerticalPosition = -1 mouseHorizontalPosition = -1 End Sub End Class