有沒有辦法獲取TreeView節點的展開/摺疊狀態？

Question

code example這顯示瞭如何得到滾動條的位置在的ScrollViewer（與ScrollToVerticalOffset），使得例如如果需要重新創建，可以將滾動條重置到此位置。

有什麼辦法可以爲TreeView控件執行此操作，即獲取用戶擴展的節點索引集合？

Answer 1

最簡單的方法是將TreeViewItem.IsExpanded屬性綁定到ViewModel，然後通過模型和計算。

我給你寫了一個例子。它計算擴展節點的數量，但你可以做你想要擴大傢伙什麼...

C＃：

using System; 
using System.Collections.ObjectModel; 
using System.ComponentModel; 
using System.Windows; 

namespace WpfApplication1 
{ 
    public partial class TestBrowser : Window 
    { 
    private TreeViewItemViewModel[] _items; 

    public TestBrowser() 
    { 
     InitializeComponent(); 

     var item1 = new TreeViewItemViewModel(); 
     var item2 = new TreeViewItemViewModel(); 
     var item3 = new TreeViewItemViewModel(); 

     item3.Children.Add(new TreeViewItemViewModel()); 
     item3.Children.Add(new TreeViewItemViewModel()); 
     var child3 = new TreeViewItemViewModel(); 
     child3.Children.Add(new TreeViewItemViewModel()); 
     item3.Children.Add(child3); 

     _items = new[] {item1, item2, item3}; 
     tv.DataContext = _items; 
    } 

     private void CalculateExpandedClick(object sender, RoutedEventArgs e) 
     { 
      var expanded = 0; 
      foreach (TreeViewItemViewModel item in _items) 
      { 
       expanded += GetNumberOfExpanded(item); 
      } 
      ExpandedNumber.Text = expanded.ToString(); 
     } 

    private int GetNumberOfExpanded(TreeViewItemViewModel model) 
    { 
     var expandedCount = 0; 
     if (model.IsExpanded) 
     { 
      expandedCount += 1; 
      foreach (TreeViewItemViewModel child in model.Children) 
      { 
       expandedCount += GetNumberOfExpanded(child); 
      } 
     } 
     return expandedCount; 
    } 
    } 

    /// <summary> 
    /// Single tree view item view model. 
    /// </summary> 
    public class TreeViewItemViewModel : INotifyPropertyChanged 
    { 
     public ObservableCollection<TreeViewItemViewModel> Children 
     { 
      get; private set; 
     } 

     private bool _isExpanded; 
     private string _text; 

     public bool IsExpanded 
     { 
      get { return _isExpanded; } 
      set 
      { 
       _isExpanded = value; 
       OnPropertyChanged("IsExpanded"); 
      } 
     } 

     public string Text 
     { 
      get { return _text; } 
      set 
      { 
       _text = value; 
       OnPropertyChanged("Text"); 
      } 
     } 

     public TreeViewItemViewModel() 
     { 
      Children = new ObservableCollection<TreeViewItemViewModel>(); 
      Text = DateTime.Now.ToLongTimeString(); // Just fake data. 
     } 

     public event PropertyChangedEventHandler PropertyChanged; 

     private void OnPropertyChanged(string name) 
     { 
      var changed = PropertyChanged; 
      if (changed != null) 
      { 
       changed(this, new PropertyChangedEventArgs(name)); 
      } 
     } 
    } 
} 

XAML：

<Window x:Class="WpfApplication1.TestBrowser" 
     xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" 
     xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" 
     Title="Expanded Test" 
     Height="300" 
     Width="300"> 
    <Grid> 
     <Grid.ColumnDefinitions> 
      <ColumnDefinition Width="*" /> 
      <ColumnDefinition Width="*" /> 
     </Grid.ColumnDefinitions> 
     <TreeView x:Name="tv" 
       ItemsSource="{Binding}"> 
      <TreeView.ItemContainerStyle> 
       <Style TargetType="{x:Type TreeViewItem}"> 
        <Setter Property="IsExpanded" Value="{Binding IsExpanded, Mode=TwoWay}" /> 
       </Style> 
      </TreeView.ItemContainerStyle> 
      <TreeView.ItemTemplate> 
       <HierarchicalDataTemplate ItemsSource="{Binding Children}"> 
        <TextBlock Text="{Binding Text}" /> 
       </HierarchicalDataTemplate> 
      </TreeView.ItemTemplate> 
     </TreeView> 

     <StackPanel Grid.Column="1"> 
      <Button Content="Get number of expanded items" 
          Click="CalculateExpandedClick"/> 
      <TextBlock x:Name="ExpandedNumber" /> 
     </StackPanel> 
    </Grid> 
</Window> 

希望這有助於。