刪除在WPF的TreeView跳到父

Question

我想在這裏討論的解決方案：WPF treeview itemselected moves incorrectly when deleting an item

但是，刪除一個項目時，我仍然看到選擇跳轉到該父。我究竟做錯了什麼？

MainWindow.xaml

<Window x:Class="TreeViewDelete.MainWindow" 
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" 
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" 
    Title="Tree View Delete sample" Height="350" Width="525"> 

<Window.Resources> 
    <Style TargetType="TreeViewItem"> 
     <Setter Property="IsSelected" Value="{Binding Selected, Mode=TwoWay}"/> 
     <EventSetter Event="KeyDown" Handler="OnTreeKeyDown"/> 
    </Style> 
    <HierarchicalDataTemplate x:Key="recursiveTemplate" ItemsSource="{Binding Children}"> 
     <StackPanel Orientation="Horizontal"> 
      <TextBlock Text="{Binding Name}"/> 
     </StackPanel> 
    </HierarchicalDataTemplate> 
</Window.Resources> 
<Grid> 
    <TreeView Name="m_tree" ItemsSource="{Binding Children}" ItemTemplate="{StaticResource recursiveTemplate}"/> 
</Grid> 
</Window> 

MainWindow.xaml.cs

public partial class MainWindow : Window 
{ 
    private Container m_root, m_child; 

    public MainWindow() 
    { 
     InitializeComponent(); 

     m_root = new Container("Root"); 

     m_child = new Container("main"); 

     m_child.Add(new Container("k1")); 
     m_child.Add(new Container("k2")); 
     m_child.Add(new Container("k3")); 
     m_child.Add(new Container("k4")); 
     m_child.Add(new Container("k5")); 

     m_root.Add(m_child); 

     m_tree.DataContext = m_root; 
    } 

    private IEnumerable<T> GetVisualAncestorsOfType<T>(DependencyObject obj) where T : DependencyObject 
    { 
     for (; obj != null; obj = VisualTreeHelper.GetParent(obj)) 
      if (obj is T) 
       yield return (T)obj; 
    } 

    private void OnTreeKeyDown(object sender, KeyEventArgs e) 
    { 
     switch (e.Key) 
     { 
      case Key.Delete: 
       { 
        TreeViewItem item = sender as TreeViewItem; 

        if (item != null) 
        { 
         Container container = item.Header as Container; 

         if (container != null) 
         { 
          Container parent = container.Parent; 

          // Find the currently focused element in the TreeView's focus scope 
          DependencyObject focused = 
           FocusManager.GetFocusedElement(
           FocusManager.GetFocusScope(m_tree)) as DependencyObject; 

          // Scan up the VisualTree to find the TreeViewItem for the parent 
          var parentContainer = (
           from element in GetVisualAncestorsOfType<FrameworkElement>(focused) 
           where (element is TreeViewItem && element.DataContext == parent) 
            || element is TreeView 
           select element 
          ).FirstOrDefault(); 

          parent.Remove(container); 

          if (parentContainer != null) 
          { 
           parent.Children[0].Selected = true; 
           parentContainer.Focus(); 
          } 
         } 
        } 

        e.Handled = true; 
       } 
       break; 
     } 
    } 
} 

最後Container.cs

public class Container : INotifyPropertyChanged 
{ 
    private bool m_selected; 
    private string m_name; 
    private ObservableCollection<Container> m_children; 
    private Container m_parent; 

    public Container(string name) 
    { 
     m_name = name; 
     m_children = new ObservableCollection<Container>(); 
     m_parent = null; 
     m_selected = false; 
    } 

    public event PropertyChangedEventHandler PropertyChanged; 

    public string Name 
    { 
     get 
     { 
      return m_name; 
     } 

     set 
     { 
      m_name = value; 

      OnPropertyChanged("Name"); 
     } 
    } 

    public Container Parent 
    { 
     get 
     { 
      return m_parent; 
     } 

     set 
     { 
      m_parent = value; 
     } 
    } 

    public bool Selected 
    { 
     get 
     { 
      return m_selected; 
     } 

     set 
     { 
      m_selected = value; 

      OnPropertyChanged("Selected"); 
     } 
    } 

    public ObservableCollection<Container> Children 
    { 
     get 
     { 
      return m_children; 
     } 
    } 

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

    public void Add(Container child) 
    { 
     m_children.Add(child); 

     child.Parent = this; 
    } 

    public void Remove(Container child) 
    { 
     m_children.Remove(child); 

     child.Parent = null; 
    } 
} 

Answer 1

我想在這裏提供的解決方案："TreeView selected item when removing nodes"和一個簡單的應用程序它精美的作品。不用說，在我正在處理的應用程序不 ...

看看這篇文章是在說什麼，似乎我需要TreeViewItem是我的項目的容器。所以我嘗試過：

m_tree.ItemContainerGenerator.ContainerFromItem 

除了這總是返回null。然後我讀到以下內容：TreeView.ItemContainerGenerator.ContainerFromItem returns null，此時我的大腦幾乎吹了一根導火線！

它似乎得到TreeViewItem我想要被選中，我必須從我的層次結構的頂部開始，並沿着樹工作，直到我到達我想要的位置。所以，我的容器數據具有Parent屬性，所以我建對象堆棧：

Stack<Containerl> stack = new Stack<Container>(); 

Container toBeSelected = ... my object to be selected after deletion ... 

while (toBeSelected != null) 
{ 
    stack.Push(toBeSelected); 

    toBeSelected = toBeSelected.Parent; 
} 

然後我從層次結構中刪除所有的項目，然後執行以下操作：

TreeViewItem item = m_tree.ItemContainerGenerator.ContainerFromItem(stack.Pop()) as TreeViewItem; 

while(item != null && (stack.Count > 0)) 
{ 
    item = item.ItemContainerGenerator.ContainerFromItem(stack.Pop()) as TreeViewItem; 
} 

// Force this item to be selected, and set focus 
item.IsSelected = true; 
item.Focus(); 

它的工作原理！ ！

Answer 2

我沒有這個檢查自己，但我認爲你可以通過使用ObservableCollections的CollectionChanged事件來做到這一點。在這裏，您可以將一個事件附加到您的子集合中，以便當其中一個被刪除時，您可以將Collection的第一個孩子的Selected屬性設置爲true。像下面的代碼：

附加事件：

Children.CollectionChanged += new System.Collections.Specialized.NotifyCollectionChangedEventHandler(Children_CollectionChanged); 

事件實現：

void Children_CollectionChanged(object sender, System.Collections.Specialized.NotifyCollectionChangedEventArgs e) 
{ 
    if (e.Action == System.Collections.Specialized.NotifyCollectionChangedAction.Remove) 
    { 
     Children.First().Selected = true; 
    } 
}