#585 – 隧道事件沿逻辑树从上至下传递(Tunneling Events Propagate Down the Logical Tree)

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在WPF中，冒泡事件从引发事件的控件开始，沿着逻辑树或者可视树向上传递。与之相反，隧道事件则是从层次结构的顶点出发，由上至下传递直到传递到引发事件的控件。

下面的代码中我们给各层的控件都注册了PreviewKeyDown 事件，然后在最下面的TextBox中按键输入。

<Window    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"    xmlns:Microsoft_Windows_Themes="clr-namespace:Microsoft.Windows.Themes;assembly=PresentationFramework.Aero"    xmlns:loc="clr-namespace:WpfApplication11"    xmlns:sys="clr-namespace:System;assembly=mscorlib"    xmlns:d="http://schemas.microsoft.com/expression/blend/2008" xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"    x:Class="WpfApplication11.MainWindow"    x:Name="Window" Title="Routed Events" Width="400"    PreviewKeyDown="winMain_PreviewKeyDown">     <StackPanel Name="spMain" Orientation="Vertical" PreviewKeyDown="spMain_PreviewKeyDown">        <Label Content="Some good movies:"/>        <StackPanel Orientation="Horizontal" Margin="10" PreviewKeyDown="spLawrence_PreviewKeyDown">            <Label Content="Lawrence of Arabia" FontWeight="Bold"/>            <Label Content="David Lean"/>            <Button Content="Like" Padding="8,0"/>            <TextBox Width="75" Margin="5,2" PreviewKeyDown="tbLawrence_PreviewKeyDown"/>        </StackPanel>    </StackPanel></Window>

显示结果：

原文地址：https://wpf.2000things.com/2012/06/21/585-tunneling-events-propagate-down-the-logical-tree/

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