WPF Behavior 行为

WPF Behavior 行为

前言

行为是一类事物的共同特征，在WPF中通过行为可以封装一些通用的界面功能，从而实现代码重用来提高开发效率。因此他是一个非常好用的工具。

引入dll文件

找到System.Windows.Interactivity.dll文件。

https://download.csdn.net/download/YouyoMei/12200463

然后将其引入到项目中。

创建行为

1.创建一个行为类LightedEffectBehavior,继承Behavior<FrameworkElement>，并指定行为覆盖元素类型FrameworkElement。意思是该行为可适用于FrameworkElement下的所有子元素。

using System.Windows;
using System.Windows.Interactivity;
using System.Windows.Media;
using System.Windows.Media.Effects;

namespace Deamon
{
    public class LightedEffectBehavior: Behavior<FrameworkElement>
    {
       
    }
}

2.重写Behavior里面的两个函数OnAttached（附加后）与OnDetaching（分离时）

using System.Windows;
using System.Windows.Interactivity;
using System.Windows.Media;
using System.Windows.Media.Effects;

namespace Deamon
{
    public class LightedEffectBehavior: Behavior<FrameworkElement>
    {
        protected override void OnAttached()
        {
            base.OnAttached();

            // AssociatedObject 是行为的关联对象，类型为我们指定的FrameworkElement
            AssociatedObject.MouseEnter += AssociatedObject_MouseEnter;
            AssociatedObject.MouseLeave += AssociatedObject_MouseLeave;
        }

        private void AssociatedObject_MouseLeave(object sender, System.Windows.Input.MouseEventArgs e)
        {
            var element = sender as FrameworkElement;
            element.Effect = new DropShadowEffect() { Color = Colors.Gold, ShadowDepth = 0 };
        }

        private void AssociatedObject_MouseEnter(object sender, System.Windows.Input.MouseEventArgs e)
        {
            var element = sender as FrameworkElement;
            element.Effect = new DropShadowEffect() { Color = Colors.Transparent, ShadowDepth = 0 };
        }

        protected override void OnDetaching()
        {
            base.OnDetaching();

            // 移除
            AssociatedObject.MouseEnter -= AssociatedObject_MouseEnter;
            AssociatedObject.MouseLeave -= AssociatedObject_MouseLeave;
        }
    }
}

3.通过AssociatedObject（关联对象：是行为的关联对象，类型为我们指定的FrameworkElement），实现实际行为的触发：鼠标移入，背景高亮效果。

3.1在OnAttached方法中添加鼠标响应事件处理方法。

3.2在OnDetaching方法中移除鼠标响应事件处理方法。

using System.Windows;
using System.Windows.Interactivity;
using System.Windows.Media;
using System.Windows.Media.Effects;

namespace Deamon
{
    public class LightedEffectBehavior: Behavior<FrameworkElement>
    {
        protected override void OnAttached()
        {
            base.OnAttached();

            // AssociatedObject 是行为的关联对象，类型为我们指定的FrameworkElement
            AssociatedObject.MouseEnter += AssociatedObject_MouseEnter;
            AssociatedObject.MouseLeave += AssociatedObject_MouseLeave;
        }

        private void AssociatedObject_MouseEnter(object sender, System.Windows.Input.MouseEventArgs e)
        {
        }

        private void AssociatedObject_MouseLeave(object sender, System.Windows.Input.MouseEventArgs e)
        {
        }

        protected override void OnDetaching()
        {
            base.OnDetaching();

            // 移除
            AssociatedObject.MouseEnter -= AssociatedObject_MouseEnter;
            AssociatedObject.MouseLeave -= AssociatedObject_MouseLeave;
        }
    }
}

4.在鼠标响应事件处理方法中实现行为。

using System.Windows;
using System.Windows.Interactivity;
using System.Windows.Media;
using System.Windows.Media.Effects;

namespace Deamon
{
    public class LightedEffectBehavior: Behavior<FrameworkElement>
    {
        protected override void OnAttached()
        {
            base.OnAttached();

            // AssociatedObject 是行为的关联对象，类型为我们指定的FrameworkElement
            AssociatedObject.MouseEnter += AssociatedObject_MouseEnter;
            AssociatedObject.MouseLeave += AssociatedObject_MouseLeave;
        }

        private void AssociatedObject_MouseEnter(object sender, System.Windows.Input.MouseEventArgs e)
        {
            var element = sender as FrameworkElement;
            // 添加一个金黄色 Effect 
            element.Effect = new DropShadowEffect() { Color = Colors.Gold, ShadowDepth = 0 };
        }

        private void AssociatedObject_MouseLeave(object sender, System.Windows.Input.MouseEventArgs e)
        {
            var element = sender as FrameworkElement;
            // 将 Effect 变成透明
            element.Effect = new DropShadowEffect() { Color = Colors.Transparent, ShadowDepth = 0 };
        }

        protected override void OnDetaching()
        {
            base.OnDetaching();

            // 移除
            AssociatedObject.MouseEnter -= AssociatedObject_MouseEnter;
            AssociatedObject.MouseLeave -= AssociatedObject_MouseLeave;
        }
    }
}

使用行为

1.添加interactivity引用

  xmlns:i="http://schemas.microsoft.com/expression/2010/interactivity"

2.使用行为

<Window x:Class="Deamon.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
        xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
        xmlns:local="clr-namespace:Deamon"
        xmlns:i="http://schemas.microsoft.com/expression/2010/interactivity"
        mc:Ignorable="d"
        Title="MainWindow" Height="450" Width="800">
    <Grid>
        <StackPanel >

            <ListBox HorizontalAlignment="Center" Margin="20">
                <ListBoxItem Content="None"/>
                <ListBoxItem Content="HasBehaviorItem">
                    <i:Interaction.Behaviors>
                        <local:LightedEffectBehavior/>
                    </i:Interaction.Behaviors>
                </ListBoxItem>
                <i:Interaction.Behaviors>
                    <local:LightedEffectBehavior/>
                </i:Interaction.Behaviors>
            </ListBox>
            
            <TextBlock Width="100" Height="30" Margin="40" Text="Hello">
                <i:Interaction.Behaviors>
                    <local:LightedEffectBehavior/>
                </i:Interaction.Behaviors>
            </TextBlock>

            <Button Width="100" Height="30" Margin="40" Content="Deamon">
                <i:Interaction.Behaviors>
                    <local:LightedEffectBehavior/>
                </i:Interaction.Behaviors>
            </Button>

            <CheckBox HorizontalAlignment="Center" Margin="40" Content="Melphily Deamon">
                <i:Interaction.Behaviors>
                    <local:LightedEffectBehavior/>
                </i:Interaction.Behaviors>
            </CheckBox>

        </StackPanel>
    </Grid>
</Window>

总结

行为与触发器有一些共同之处，很多时候可以直接使用触发器来代替，但是在做一些通用的功能时，行为不失为很好的解决方案。

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