这一节，我们来利用Behavior行为实现控件的缩放效果。要实现此效果，需要在鼠标的滚轮事件下，通过获取Delta值去设置ScaleTransform缩放对象的ScaleX和ScaleY，从而将控件进行放大或缩小。

下面是缩放行为的定义代码：

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

        AssociatedObject.MouseWheel += AssociatedObject_MouseWheel;
    }

    private void AssociatedObject_MouseWheel(object sender, 
        System.Windows.Input.MouseWheelEventArgs e)
    {
        //首次滚动时，判断RenderTransform的类型是否为ScaleTransform
        if (!(AssociatedObject.RenderTransform is ScaleTransform))
        {
            AssociatedObject.RenderTransform = new ScaleTransform()
            {
                CenterX = AssociatedObject.ActualWidth / 2,
                CenterY = AssociatedObject.ActualHeight / 2,
            };
        }

        var transform = AssociatedObject.RenderTransform as ScaleTransform;
        double scale = e.Delta * 0.001;
        transform.ScaleX += scale;
        transform.ScaleY += scale;
    }

    protected override void OnDetaching()
    {
        base.OnDetaching();
        AssociatedObject.MouseWheel -= AssociatedObject_MouseWheel;
    }        
}

然后，我们在上一节的代码中稍作修改，引用这个行为。

<Window x:Class="HelloWorld.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:HelloWorld" 
        xmlns:controls="clr-namespace:HelloWorld.Controls"
        xmlns:helper="clr-namespace:HelloWorld.MVVM" 
        xmlns:i="http://schemas.microsoft.com/xaml/behaviors" 
        xmlns:behavior="clr-namespace:HelloWorld.Behaviors"
        mc:Ignorable="d" Background="DarkCyan"
        Title="WPF中文网 - 行为 - www.wpfsoft.com" Height="350" Width="500">
    <Window.DataContext>
        <local:MainViewModel/>
    </Window.DataContext>
    <Canvas>
        <Border Width="50" Height="50" CornerRadius="50" 
                Background="LightGoldenrodYellow" 
                Canvas.Left="228" Canvas.Top="20">
            <i:Interaction.Behaviors>
                <behavior:ShadowBehavior/>
                <behavior:ScaleBehavior/>
            </i:Interaction.Behaviors>
        </Border>
        <TextBlock Text="WPF中文网" 
                   Foreground="White" 
                   FontSize="60" 
                   Canvas.Left="92" 
                   Canvas.Top="75">
            <i:Interaction.Behaviors>
                <behavior:ShadowBehavior/>
                <behavior:ScaleBehavior/>
            </i:Interaction.Behaviors>
        </TextBlock>
        <TextBlock Text="Behavior行为之缩放效果" 
                   Foreground="White" 
                   FontSize="40" 
                   Canvas.Left="21" 
                   Canvas.Top="182">
            <i:Interaction.Behaviors>
                <behavior:ShadowBehavior/>
                <behavior:ScaleBehavior/>
            </i:Interaction.Behaviors>
        </TextBlock>       
    </Canvas>
</Window>

缩放之前的效果

缩放之后的效果

当前课程源码下载：（注明：本站所有源代码请按标题搜索）

文件名：109-《行为之控件缩放效果》-源代码
链接：https://pan.baidu.com/s/1yu-q4tUtl0poLVgmcMfgBA
提取码：wpff

——重庆教主 2023年11月21日