wpf - RadioButton 被选中，运行应用时调用它的 Checked 事件，并报告异常

Question

里面有两个RadioButtons和两个Labels .xaml，勾选一个RadioButton使对应的LabelEnable。RadioButton1被检查。运行app，Checked Event会自动调用，但是Label为null，所以app报异常。

我只是使用一个变量来标记窗口是否是第一次创建的。是否还有其他方法？我不知道为什么应用程序在初始化所有组件后运行事件，谁能告诉我？

主窗口.xaml

<Window x:Class="WpfApplication7.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">
    <StackPanel>
        <RadioButton
            GroupName="Group"
            IsChecked="True"
            Content="RadioButton1"
            x:Name="RadioButton1"
            Checked="RadioButton1_Checked"
            Unchecked="RadioButton1_Unchecked"/>
        <RadioButton
            GroupName="Group"
            Content="RadioButton2"
            x:Name="RadioButton2"
            Checked="RadioButton2_Checked"
            Unchecked="RadioButton2_Unchecked"/>
        <Label
            x:Name="Label1"
            Content="Label1"/>
        <Label
            IsEnabled="False"
            x:Name="Label2"
            Content="Label2"/>
    </StackPanel>
</Window>

主窗口.xaml.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
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 WpfApplication7
{
    /// <summary>
    /// MainWindow.xaml
    /// </summary>
    public partial class MainWindow : Window
    {
        private bool isFirstRun;

        public MainWindow()
        {
            isFirstRun = true;

            InitializeComponent();

            isFirstRun = false;
        }

        private void RadioButton1_Checked(object sender, RoutedEventArgs e)
        {
            if (isFirstRun)
                return;
            Label1.IsEnabled = true;
        }

        private void RadioButton2_Checked(object sender, RoutedEventArgs e)
        {
            Label1.IsEnabled = false;
        }

        private void RadioButton1_Unchecked(object sender, RoutedEventArgs e)
        {
            Label2.IsEnabled = true;
        }

        private void RadioButton2_Unchecked(object sender, RoutedEventArgs e)
        {
            Label2.IsEnabled = false;
        }
    }
}

Answer 1

我不确定您是否有特定原因EventHandlers，但如果没有，您可以直接在XamlusingElementName绑定中执行此逻辑

例子：

 <StackPanel>
        <RadioButton x:Name="RadioButton1"
                     GroupName="Group"
                     IsChecked="True"
                     Content="RadioButton1" />

        <RadioButton x:Name="RadioButton2"
                     GroupName="Group"
                     Content="RadioButton2" />

        <Label x:Name="Label1"
               IsEnabled="{Binding IsChecked, ElementName=RadioButton1}"
               Content="Label1"/>

        <Label x:Name="Label2"
               IsEnabled="{Binding IsChecked, ElementName=RadioButton2}"
               Content="Label2"/>
    </StackPanel>

Answer 2

为什么不简单地Ischecked="True"从 XAML中删除isFirstRun = false并将之后设置的变量InitializeComponent();替换为RadioButton1.IsChecked = true

这样您就不必定义isFirstRun变量了。