Silverlight实例开发 简单的拖拽效果

Silverlight 2完美征程学习笔记
拖拽效果分为3个步骤
按下鼠标，触发MouseLeftButtonDown事件，选择要拖动的对象
移动鼠标，触发MouseMove事件，移动选择的对象
放开鼠标，触发MouseLeftButtonUp事件，停止捕捉事件
页面代码：

 

开始拖放操作，实现MouseLeftButtonDown事件的处理

private void StackPanel_MouseLeftButtonDown(object sender, MouseButtonEventArgs e)
{
FrameworkElement element = sender as FrameworkElement;
mousePosition = e.GetPosition(null);
trackingMouseMove = true;

if(null!=element)
{
element.CaptureMouse();
element.Cursor = Cursors.Hand;
}
txtStatus.Text = "MouseLeftButtonDown";
}

移动对象，实现 MouseMove事件处理程序，计算元素的位置并更新，同时更新鼠标的位置

private void StackPanel_MouseMove(object sender, MouseEventArgs e)
{
FrameworkElement element = sender as FrameworkElement;

if(trackingMouseMove)
{
double deltaV = e.GetPosition(null).Y - mousePosition.Y;
double deltaH = e.GetPosition(null).X - mousePosition.X;
double newTop = deltaV + (double) element.GetValue(Canvas.TopProperty);
double newLeft = deltaH + (double) element.GetValue(Canvas.LeftProperty);

element.SetValue(Canvas.TopProperty, newTop);
element.SetValue(Canvas.LeftProperty, newLeft);
mousePosition = e.GetPosition(null);
}

txtStatus.Text = "Mouse Moving ……";
}

 

完成拖放操作，释放鼠标，实现MouseLeftButtonUp事件处理程序

private void StackPanel_MouseLeftButtonUp(object sender, MouseButtonEventArgs e)
{
FrameworkElement element = sender as FrameworkElement;
trackingMouseMove = false;
element.ReleaseMouseCapture();

mousePosition.X = mousePosition.Y = 0;
element.Cursor = null;

txtStatus.Text = "ReleaseMouse";
}