鼠标事件-矩形移动

可以把Rectangle改为其他控件，如Panel，实现类似操作。

在MainPage.xaml中：

<Canvas x:Name="rootCanvas" Width="400" Height="300" Background="Gray">
        <Rectangle Canvas.Left="30" Canvas.Top="30" Fill="Red" Width="50" Height="50"
                   MouseLeftButtonDown="Rectangle_MouseLeftButtonDown" 
                   MouseMove="Rectangle_MouseMove"
                   MouseLeftButtonUp="Rectangle_MouseLeftButtonUp"> 
        </Rectangle> 
    </Canvas>

在MainPage.xaml.cs中：

 private void Rectangle_MouseLeftButtonDown(object sender, MouseButtonEventArgs e)
        {
            Rectangle item = sender as Rectangle;
            //null是绝对位置，如果是某个控件则是相对这个控件的位置
            mouseVerticalPosition = e.GetPosition(null).Y;
            mouseHorizontalPosition = e.GetPosition(null).X;
            isMouseCaptured = true;
            item.CaptureMouse();//开始捕获鼠标
        }

        private void Rectangle_MouseMove(object sender, MouseEventArgs e)
        {
            Rectangle item = sender as Rectangle;
            if(isMouseCaptured)
            {
                //计算鼠标变化量
                double detaY = e.GetPosition(null).Y - mouseVerticalPosition;
                double detaX = e.GetPosition(null).X - mouseHorizontalPosition;
                //获取矩形新的top和left值
                double newTop = detaY + (double)item.GetValue(Canvas.TopProperty);
                double newLeft = detaX + (double)item.GetValue(Canvas.LeftProperty);
                //设置新的坐标值
                item.SetValue(Canvas.TopProperty, newTop);
                item.SetValue(Canvas.LeftProperty, newLeft);
                //保存现在的鼠标坐标
                mouseHorizontalPosition = e.GetPosition(null).X;
                mouseVerticalPosition = e.GetPosition(null).Y;
            }
            else
            {

            }
        }

        private void Rectangle_MouseLeftButtonUp(object sender, MouseButtonEventArgs e)
        {
            Rectangle item = sender as Rectangle;
            //释放鼠标
            isMouseCaptured = false;
            item.ReleaseMouseCapture();
            mouseHorizontalPosition = -1;
            mouseVerticalPosition = -1;
        }