Question

我尝试了这里讨论的解决方案：WPF treeview itemselected moves incorrectly when deleting an item

但是，在删除项目时，我仍然看到选择跳转到该父项。我做错了什么？

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;
        }
    }
}

最后是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

我自己没有检查过，但我认为你可以通过使用ObservableCollections的CollectionChanged事件来实现这一点。在这里，您可以将一个事件附加到您的子集合中，以便在删除其中一个集合时，您可以将Selected的属性（例如集合的第一个子集）设置为true。类似下面的代码：

附上活动：

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

事件实施：

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

Answer 2

我尝试了这里提供的解决方案："TreeView selected item when removing nodes"并且在一个简单的应用程序中它可以很好地工作。毋庸置疑，在我正在开发的应用程序中不 ......

看看文章的内容，似乎我需要TreeViewItem作为我项目的容器。所以我试过了：

m_tree.ItemContainerGenerator.ContainerFromItem

除此之外总是返回null。然后我读了以下内容：TreeView.ItemContainerGenerator.ContainerFromItem returns null，此时我的大脑几乎吹了一根导火索！

似乎想要选择TreeViewItem，我必须从我的层次结构的顶部开始，然后在树上工作，直到我到达我想要的地方。所以，我的容器数据有一个Parent属性，所以我构建了一堆对象：

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

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

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

    toBeSelected = toBeSelected.Parent;
}

然后我删除了我的层次结构中的所有项目，然后执行以下操作：

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();

它有效!!!

在WPF中删除TreeView会跳转到父级

2 个答案: