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="350" Width="525">
    <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="350" Width="525">
    <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="0">
                    <TextBlock DockPanel.Dock="Top" Text="逻辑树"></TextBlock>
                    <TreeView Name="tvLogicTree"></TreeView>
                </DockPanel>
                <DockPanel Grid.Column="1">
                    <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 = 0; 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