WPF 中使用行为示例——Canvas控件拖放行为的演示

 资料来源：WPF编程宝典P272

1、获取行为的支持，安装Expression Blend 4  SDK（http://www.microsoft.com/zh-cn/download/details.aspx?id=10801） 。

 

2、创建行为库

（1）创建一个Class Project，添加WPF必备的以及WPF中支持行为必备的dll文件。

       其中，System.Windows.Interactivity.dll组件在目录（需要安装Blend SDKs）：C:\Program Files (x86)\Microsoft SDKs\Expression\Blend\.NETFramework\v4.0\Libraries。

 

 

（2）创建DragInCanvasBehavior.cs，继承类Behavior<UIElement>，overrideBehavior<UIElement>得OnAttached()和OnDetaching()方法，代码如下：。

 1 protected override void OnAttached()
 2         {
 3             base.OnAttached();
 4             this.AssociatedObject.MouseLeftButtonDown += AssociatedObject_MouseLeftButtonDown;
 5             this.AssociatedObject.MouseLeftButtonUp += AssociatedObject_MouseLeftButtonUp;
 6             this.AssociatedObject.MouseMove += AssociatedObject_MouseMove;
 7         }
 8 
 9         /// <summary>
10         /// Behavior.OnDetaching()，移出事件处理程序
11         /// </summary>
12         protected override void OnDetaching()
13         {
14             base.OnDetaching();
15             this.AssociatedObject.MouseLeftButtonDown -= AssociatedObject_MouseLeftButtonDown;
16             this.AssociatedObject.MouseLeftButtonUp -= AssociatedObject_MouseLeftButtonUp;
17             this.AssociatedObject.MouseMove -= AssociatedObject_MouseMove;
18         }

（3）添加的行为的事件处理程序

 1 private void AssociatedObject_MouseLeftButtonDown(object sender, System.Windows.Input.MouseButtonEventArgs e)
 2         {
 3             if (canvas == null)
 4             {
 5                 canvas = VisualTreeHelper.GetParent(this.AssociatedObject) as Canvas;
 6             }
 7             if (canvas != null)
 8             {
 9                 isDragging = true;
10                 mouseOffset = e.GetPosition(this.AssociatedObject);
11                 AssociatedObject.CaptureMouse();
12             }
13         }
14 
15         private void AssociatedObject_MouseMove(object sender, System.Windows.Input.MouseEventArgs e)
16         {
17             if (canvas != null && isDragging == true)
18             {
19                 Point p = e.GetPosition(canvas);
20                 AssociatedObject.SetValue(Canvas.TopProperty, p.Y - mouseOffset.Y);
21                 AssociatedObject.SetValue(Canvas.LeftProperty, p.X - mouseOffset.X);
22             }
23         }
24 
25         private void AssociatedObject_MouseLeftButtonUp(object sender, System.Windows.Input.MouseButtonEventArgs e)
26         {
27             if (isDragging)
28             {
29                 AssociatedObject.ReleaseMouseCapture();
30                 isDragging = false;
31             }
32         }

（4）使用行为

在WPF Application中添加Class Library和System.Windows.Interactivity.dll

① 添加XML映射名称空间

 

② 使用代码

<Canvas >
        <Label x:Name="label" Content="我是中国人" Background="LemonChiffon" Width="240" HorizontalContentAlignment="Center" FontSize="16">
            <i:Interaction.Behaviors>
               <custom:DragInCanvasBehavior></custom:DragInCanvasBehavior>
            </i:Interaction.Behaviors>
        </Label>
        <Label x:Name="label2" Content="我是中国人" Background="LemonChiffon" Width="240" HorizontalContentAlignment="Center" FontSize="16">
            <i:Interaction.Behaviors>
                <custom:DragInCanvasBehavior></custom:DragInCanvasBehavior>
            </i:Interaction.Behaviors>
        </Label>
    </Canvas>

（5） 运行效果

 

 

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