强制三态复选框不移动到不确定状态

Question

嗨,我在WPF工作,我有一个有趣的要求.我需要我的复选框是ThreeState,所以如果只选择了一些子元素,它会显示为不确定.但是当用户点击它时,我希望它选择true或false.

这是一个代表我的要求的故事:

item - indeterminate  
    subItem - checked  
    subItem - unchecked  
    subItem - checked  

当用户点击时item,复选框应在已选中和未选中之间切换.用户永远不能选择"不确定"作为状态.这可能吗？

Answer 1

XAML:

<CheckBox IsThreeState="True" IsChecked="{x:Null}" Click="CheckBox_Clicked" />

代码隐藏:

private void CheckBox_Clicked(object sender, RoutedEventArgs e)
  {
     var cb = e.Source as CheckBox;
     if (!cb.IsChecked.HasValue) 
        cb.IsChecked = false;
  }

如果您不喜欢代码隐藏解决方案,那么您可以像对待此问题的解决方案一样对您自己的控件进行子类化.

Answer 2

如果你使用CheckBox与Binding一起使用会容易得多.

XAML:

<Window x:Class="WpfApplication39Checkbox.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>
        <CheckBox Content="CheckBox" HorizontalAlignment="Left" Margin="128,95,0,0" VerticalAlignment="Top" IsThreeState="False" IsChecked="{Binding CheckState}"/>
        <Button Content="Button" HorizontalAlignment="Left" Margin="46,241,0,0" VerticalAlignment="Top" Width="75" Click="Button_Click"/>
        <Button Content="Button" HorizontalAlignment="Left" Margin="139,241,0,0" VerticalAlignment="Top" Width="75" Click="Button_Click_1"/>
        <Button Content="Button" HorizontalAlignment="Left" Margin="235,241,0,0" VerticalAlignment="Top" Width="75" Click="Button_Click_2"/>
    </Grid>
</Window>

代码隐藏:

using System.ComponentModel;
using System.Runtime.CompilerServices;
using System.Windows;

namespace WpfApplication39Checkbox
{
    /// <summary>
    /// Interaction logic for MainWindow.xaml
    /// </summary>
    public partial class MainWindow : Window, INotifyPropertyChanged
    {
        public MainWindow()
        {
            InitializeComponent();
            DataContext = this;
        }

        private bool? checkState;

        public bool? CheckState
        {
            get { return checkState; }
            set
            {
                checkState = value;
                OnPropertyChanged("CheckState");
            }
        }

        private void Button_Click(object sender, RoutedEventArgs e)
        {
            CheckState = false;
        }

        private void Button_Click_1(object sender, RoutedEventArgs e)
        {
            CheckState = true;
        }

        private void Button_Click_2(object sender, RoutedEventArgs e)
        {
            CheckState = null;
        }

        public event PropertyChangedEventHandler PropertyChanged;

        protected virtual void OnPropertyChanged([CallerMemberName] string propertyName = null)
        {
            PropertyChangedEventHandler handler = PropertyChanged;
            if (handler != null) handler(this, new PropertyChangedEventArgs(propertyName));
        }
    }
}

你明白了吗？您将CheckBox设置为IsThreeState ="False",但从CodeBehind设置第三个状态,CheckBox按预期运行.