WPF路由事件一：逻辑树和可视树

一、什么是逻辑树

逻辑树就是描述WPF界面元素的实际构成，它是由程序在XAML中所有的UI元素组成。最显著的特点就是由布局控件、或者其他常用的控件组成。

 <Window x:Class="WpfRouteEvent.MainWindow"
         xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
         xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
         Title="MainWindow" Height="" Width="">
     <Grid>
         <StackPanel>
             <TextBox></TextBox>
         </StackPanel>
     </Grid>
 </Window>

从上面的代码中可以看出，Window、Grid、StackPanel、TextBox其实就是XAML界面的逻辑树。

二、什么是可视树

可视树是由界面上可见的元素构成的，这些元素主要是由从Visual或者Visual3D类中派生出来的类。

上面代码中的Window、Grid、StackPanel、TextBox它们本身就包含一些由Visual或者Visual3D类派生出的一些可视树的元素来组成的。

三、逻辑树和可视树的遍历

逻辑树遍历使用LogicalTreeHelper类。
可视树遍历使用VisualTreeHelper类。

演示遍历逻辑树和可视树

1、XAML界面左边显示逻辑树，右边显示可视树，代码如下：

 <Window x:Class="WpfRouteEvent.MainWindow"
         xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
         xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
         Title="MainWindow" Height="" Width="">
     <Grid>
         <DockPanel>
             <Button DockPanel.Dock="Top" Click="Button_Click" Content="获取逻辑树和可视树"></Button>
             <Grid>
                 <Grid.ColumnDefinitions>
                     <ColumnDefinition></ColumnDefinition>
                     <ColumnDefinition></ColumnDefinition>
                 </Grid.ColumnDefinitions>
                 <DockPanel Grid.Column="">
                     <TextBlock DockPanel.Dock="Top" Text="逻辑树"></TextBlock>
                     <TreeView Name="tvLogicTree"></TreeView>
                 </DockPanel>
                 <DockPanel Grid.Column="">
                     <TextBlock DockPanel.Dock="Top" Text="可视树"></TextBlock>
                     <TreeView Name="tvVisualTree"></TreeView>
                 </DockPanel>
             </Grid>
         </DockPanel>

     </Grid>
 </Window>

2、添加类，用于遍历整个XAML界面的逻辑树和可视树

 using System;
 using System.Collections.Generic;
 using System.Linq;
 using System.Text;
 using System.Threading.Tasks;
 using System.Windows;
 using System.Windows.Controls;
 using System.Windows.Media;

 namespace WpfRouteEvent
 {
     public class WpfTreeHelper
     {
         static string GetTypeDescription(object obj)
         {
             return obj.GetType().FullName;
         }

         /// <summary>
         /// 获取逻辑树
         /// </summary>
         /// <param name="obj"></param>
         /// <returns></returns>
         public static TreeViewItem GetLogicTree(DependencyObject obj)
         {
             if (obj == null)
             {
                 return null;
             }
             //创建逻辑树的节点
             TreeViewItem treeItem = new TreeViewItem {Header=GetTypeDescription(obj),IsExpanded=true };

             //循环遍历，获取逻辑树的所有子节点
             foreach (var child in LogicalTreeHelper.GetChildren(obj))
             {
                 //递归调用
                 var item = GetLogicTree(child as DependencyObject);
                 if (item != null)
                 {
                     treeItem.Items.Add(item);
                 }
             }

             return treeItem;
         }

         /// <summary>
         /// 获取可视树
         /// </summary>
         /// <param name="obj"></param>
         /// <returns></returns>
         public static TreeViewItem GetVisualTree(DependencyObject obj)
         {
             if (obj == null)
             {
                 return null;
             }

             TreeViewItem treeItem = new TreeViewItem { Header=GetTypeDescription(obj),IsExpanded=true};

             for (int i = ; i < VisualTreeHelper.GetChildrenCount(obj); i++)
             {
                 var child = VisualTreeHelper.GetChild(obj, i);
                 var item = GetVisualTree(child);
                 if (item != null)
                 {
                     treeItem.Items.Add(item);
                 }
             }

             return treeItem;
         }
     }
 }

3、在按钮的点击事件中将获取的逻辑树和可视树添加到XAML界面中

 using System;
 using System.Collections.Generic;
 using System.Linq;
 using System.Text;
 using System.Threading.Tasks;
 using System.Windows;
 using System.Windows.Controls;
 using System.Windows.Data;
 using System.Windows.Documents;
 using System.Windows.Input;
 using System.Windows.Media;
 using System.Windows.Media.Imaging;
 using System.Windows.Navigation;
 using System.Windows.Shapes;

 namespace WpfRouteEvent
 {
     /// <summary>
     /// MainWindow.xaml 的交互逻辑
     /// </summary>
     public partial class MainWindow : Window
     {
         public MainWindow()
         {
             InitializeComponent();
         }

         private void Button_Click(object sender, RoutedEventArgs e)
         {
             this.tvLogicTree.Items.Add(WpfTreeHelper.GetLogicTree(this));
             this.tvVisualTree.Items.Add(WpfTreeHelper.GetVisualTree(this));
         }
     }
 }

4、点击按钮，界面运行效果