silverlight canvas 鼠标拖动canvas

本节举一个例子，该示例与本书第六章的示例程序大致相同，示例程序运行效果如图所示。

示例中的两个图形分别包含在两个子画布中，这两个子画布共享相同的事件处理器，分别是MouseLeftButtonDown、MouseMove和MouseLeftButtonUp事件，XAML代码如下所示。

<Canvas x:Name="parentCanvas"

        xmlns="http://schemas.microsoft.com/client/2007"

        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"

        Loaded="Page_Loaded"

        x:Class="DragandDropDemo.Page;assembly=ClientBin/DragandDropDemo.dll"

        Width="640"

        Height="480"

        Background="White"

        >

  <!-- 定义两个圆形对象，形成一个圆环效果-->

  <Canvas

    MouseLeftButtonDown="onMouseDown"

    MouseLeftButtonUp="onMouseUp"

    MouseMove="onMouseMove"

    Canvas.Top="20" Canvas.Left="50">

    <Ellipse

      Height="100" Width="100"

      Fill="Gold"

      Stroke="Black" StrokeThickness="4" />

    <Ellipse

      Height="50" Width="50"

      Canvas.Top="25" Canvas.Left="25"

      Fill="Black" />

  </Canvas>

  <!-- 定义一个钻石形状 -->

  <Canvas

    MouseLeftButtonDown="onMouseDown"

    MouseLeftButtonUp="onMouseUp"

    MouseMove="onMouseMove"

    Canvas.Top="140" Canvas.Left="100">

    <!--使用旋转渐变让该画布旋转45度-->

    <Canvas.RenderTransform>

      <RotateTransform Angle="45" />

    </Canvas.RenderTransform> 

    <Rectangle

      Height="100" Width="100"

      Fill="Coral"

      Stroke="Black" StrokeThickness="4" />

  </Canvas>

</Canvas>

上面的代码很简单的画了两个图形，分别位于两个画布中，拖动的实际代码如下所示。

using System;

using System.Windows;

using System.Windows.Controls;

using System.Windows.Documents;

using System.Windows.Ink;

using System.Windows.Input;

using System.Windows.Media;

using System.Windows.Media.Animation;

using System.Windows.Shapes;

namespace DragandDropDemo

{

    public partial class Page : Canvas

    {

        //beginX和beginY用于保存鼠标上一次的位置

        private double beginX;

        private double beginY;

        //isMouseDown获取和设置鼠标是否按下的布尔变量

        private bool isMouseDown = false;

        public void Page_Loaded(object o, EventArgs e)

        {

            // Required to initialize variables

            InitializeComponent();

        }

        //鼠标左键按下时的事件代码

        public void onMouseDown(object sender, MouseEventArgs e)

        {

            //将当前的鼠标位置传给私有变量

            beginX = e.GetPosition(null).X;

            beginY = e.GetPosition(null).Y;

            //将isMouseDown设为true表示鼠标按下。

            isMouseDown = true;

            //由于CaptureMouse都定义在UIElement中，所以这里、转换为UIElement类

            ((UIElement)sender).CaptureMouse();

        }

        //鼠标移动

        public void onMouseMove(object sender, MouseEventArgs e)

        {

            //如果鼠标处理按下状态

            if (isMouseDown == true)

            {

                //获取鼠标当前位置

                double currX = e.GetPosition(null).X;

                double currY = e.GetPosition(null).Y;

                //获取当前图形的位置

                double currLeft = (double)((UIElement)sender).GetValue(Canvas.LeftProperty);

                double currTop = (double)((UIElement)sender).GetValue(Canvas.TopProperty);

                //移动当前图形的位置

((UIElement)sender).SetValue(Canvas.LeftProperty, currLeft + currX - beginX);

                ((UIElement)sender).SetValue(Canvas.TopProperty, currTop + currY - beginY);

                //将当前位置保存起来，继续拖动。

                beginX = currX;

                beginY = currY;

            }

        }

        //释放鼠标左键

        public void onMouseUp(object sender, MouseEventArgs e)

        {           

            isMouseDown = false;

            //停止鼠标捕捉

            ((UIElement)sender).ReleaseMouseCapture();

        }

    }

}

来源于http://blog.csdn.net/silverlightria/article/details/2323740