一次只选择一个项目的多个WPF列表框

Question

我正在使用MVVM并在一个窗口中显示两个列表框。我将这两个列表框同时绑定到不同的字段上，称为A和B.然后A和B都修改C.为了实现这个功能，我只想从两个列表框中选择一个IsSelected，这样A当B IsSelected时不覆盖C.我怎样才能限制呢？

谢谢！

Answer 1

我可以想到几种方法来做到这一点。

一种方法是您可以绑定您的2个ListBoxes的ListBox.SelectedIndex来更改 - 通知ViewModel属性。

例如，在您查看：

<ListBox SelectedIndex="{Binding SelectedIndexA}"> 
    <ListBoxItem Content="Item 1"/> 
    <ListBoxItem Content="Item 2"/> 
</ListBox> 
<ListBox SelectedIndex="{Binding SelectedIndexB}"> 
    <ListBoxItem Content="Item 1"/> 
    <ListBoxItem Content="Item 2"/> 
</ListBox> 

而在你的ViewModel：

public int SelectedIndexA 
{ 
    get { return _selectedIndexA; } 
    set 
    { 
     _selectedIndexA = value; 
     _selectedIndexB = -1; 
     OnPropertyChanged("SelectedIndexB"); 
    } 
} 

public int SelectedIndexB 
{ 
    get { return _selectedIndexB; } 
    set 
    { 
     _selectedIndexB = value; 
     _selectedIndexA = -1; 
     OnPropertyChanged("SelectedIndexA"); 
    } 
} 

另一种方法是用像“组名”附加属性其中您可以选择器（ListBox从继承Selector）以确保组中只有一个Selector在任何时间都有选定的项目。

例如：

public static class SingleSelectionGroup 
{ 
    public static readonly DependencyProperty GroupNameProperty = 
     DependencyProperty.RegisterAttached("GroupName", typeof(string), typeof(SingleSelectionGroup), 
              new UIPropertyMetadata(OnGroupNameChanged)); 

    public static string GetGroupname(Selector selector) 
    { 
     return (string) selector.GetValue(GroupNameProperty); 
    } 

    public static void SetGroupName(Selector selector, string value) 
    { 
     selector.SetValue(GroupNameProperty, value); 
    } 

    private static void OnGroupNameChanged(DependencyObject dependencyObject, DependencyPropertyChangedEventArgs e) 
    { 
     var selector = (Selector) dependencyObject; 

     if (e.OldValue != null) 
      selector.SelectionChanged -= SelectorOnSelectionChanged; 
     if (e.NewValue != null) 
      selector.SelectionChanged += SelectorOnSelectionChanged; 
    } 

    private static void SelectorOnSelectionChanged(object sender, SelectionChangedEventArgs e) 
    { 
     if (e.AddedItems.Count == 0) 
      return; 

     var selector = (Selector) sender; 
     var groupName = (string) selector.GetValue(GroupNameProperty); 
     var groupSelectors = GetGroupSelectors(selector, groupName); 

     foreach (var groupSelector in groupSelectors.Where(gs => !gs.Equals(sender))) 
     { 
      groupSelector.SelectedIndex = -1; 
     } 
    } 

    private static IEnumerable<Selector> GetGroupSelectors(DependencyObject selector, string groupName) 
    { 
     var selectors = new Collection<Selector>(); 
     var parent = GetParent(selector); 
     GetGroupSelectors(parent, selectors, groupName); 
     return selectors; 
    } 

    private static DependencyObject GetParent(DependencyObject depObj) 
    { 
     var parent = VisualTreeHelper.GetParent(depObj); 
     return parent == null ? depObj : GetParent(parent); 
    } 

    private static void GetGroupSelectors(DependencyObject parent, Collection<Selector> selectors, string groupName) 
    { 
     var childrenCount = VisualTreeHelper.GetChildrenCount(parent); 
     for (int i = 0; i < childrenCount; i++) 
     { 
      var child = VisualTreeHelper.GetChild(parent, i); 
      var selector = child as Selector; 
      if (selector != null && (string) selector.GetValue(GroupNameProperty) == groupName) 
       selectors.Add(selector); 

      GetGroupSelectors(child, selectors, groupName); 
     } 
    } 
} 

而在你的视野：

<ListBox my:SingleSelectionGroup.GroupName="Group A"> 
    <ListBoxItem Content="Item 1 (Group A)"/> 
    <ListBoxItem Content="Item 2 (Group A)"/> 
</ListBox> 
<ListBox my:SingleSelectionGroup.GroupName="Group A"> 
    <ListBoxItem Content="Item 1 (Group A)"/> 
    <ListBoxItem Content="Item 2 (Group A)"/> 
</ListBox> 

<ListBox my:SingleSelectionGroup.GroupName="Group B"> 
    <ListBoxItem Content="Item 1 (Group B)"/> 
    <ListBoxItem Content="Item 2 (Group B)"/> 
</ListBox> 
<ListBox my:SingleSelectionGroup.GroupName="Group B"> 
    <ListBoxItem Content="Item 1 (Group B)"/> 
    <ListBoxItem Content="Item 2 (Group B)"/> 
</ListBox> 

如果你必须点击一个项目之前两次将突出显示，你可以使用一个快速的解决方法是这样的：

<Style TargetType="ListBoxItem"> 
    <Style.Triggers> 
     <EventTrigger RoutedEvent="GotKeyboardFocus"> 
      <BeginStoryboard> 
       <Storyboard> 
        <BooleanAnimationUsingKeyFrames Storyboard.TargetProperty="(ListBoxItem.IsSelected)"> 
         <DiscreteBooleanKeyFrame KeyTime="00:00:00" Value="True" /> 
        </BooleanAnimationUsingKeyFrames> 
       </Storyboard> 
      </BeginStoryboard> 
     </EventTrigger> 
    </Style.Triggers> 
</Style> 

Answer 2

如果有人在ItemsControl中使用了ListBox/ListView，并且存在以下问题使用上述答案后：

1. 当您单击listbox1中的任何项目时，该项目被选中。
2. 当您单击列表框2中的任何项目时，所选的列表框1的项目未被选中，但列表框2中的项目未被选中。
3. 当您再次点击listbox2中的任何项目时，该项目被选中。

以下XAML只需添加到您的ListBoxItem的风格：

<Style TargetType="ListBoxItem"> 
    <Style.Triggers> 
     <Trigger Property="IsKeyboardFocusWithin" Value="True"> 
      <Setter Property="IsSelected" Value="True"></Setter> 
     </Trigger> 
    </Style.Triggers> 
</Style> 

而且，如果有人在上面的回答使用代码后发现了以下错误：

GroupName is already registered by Selector 

请将依赖项属性声明中的third parameter typeof(......)更改为您的类名称。