WPF Behavior 行爲

WPF Behavior 行爲

前言

行爲是一類事物的共同特徵，在WPF中通過行爲可以封裝一些通用的界面功能，從而實現代碼重用來提高開發效率。因此他是一個非常好用的工具。

引入dll文件

找到System.Windows.Interactivity.dll文件。

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

然後將其引入到項目中。

創建行爲

1.創建一個行爲類LightedEffectBehavior,繼承Behavior<FrameworkElement>，並指定行爲覆蓋元素類型FrameworkElement。意思是該行爲可適用於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.重寫Behavior裏面的兩個函數OnAttached（附加後）與OnDetaching（分離時）

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 是行爲的關聯對象，類型爲我們指定的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.通過AssociatedObject（關聯對象：是行爲的關聯對象，類型爲我們指定的FrameworkElement），實現實際行爲的觸發：鼠標移入，背景高亮效果。

3.1在OnAttached方法中添加鼠標響應事件處理方法。

3.2在OnDetaching方法中移除鼠標響應事件處理方法。

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 是行爲的關聯對象，類型爲我們指定的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.在鼠標響應事件處理方法中實現行爲。

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 是行爲的關聯對象，類型爲我們指定的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;
            // 添加一個金黃色 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;
            // 將 Effect 變成透明
            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;
        }
    }
}

使用行爲

1.添加interactivity引用

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

2.使用行爲

<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>

總結

行爲與觸發器有一些共同之處，很多時候可以直接使用觸發器來代替，但是在做一些通用的功能時，行爲不失爲很好的解決方案。

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