Enlazar SelectedItem en una WPF TreeView aplicada a HierarchicalDataTemplate

data-binding treeviewitem

Question

Tengo un TreeView enlazado a datos y quiero enlazar SelectedItem . Este comportamiento adjunto funciona perfectamente sin HierarchicalDataTemplate pero con él, el comportamiento adjunto solo funciona de una manera (UI a datos) y no del otro porque ahora e.NewValue es MyViewModel no TreeViewItem .

Este es un fragmento de código del comportamiento adjunto:

private static void OnSelectedItemChanged(DependencyObject sender, DependencyPropertyChangedEventArgs e)
{
    var item = e.NewValue as TreeViewItem;
    if (item != null)
    {
        item.SetValue(TreeViewItem.IsSelectedProperty, true);
    }
}

Esta es mi definición TreeView :

<Window xmlns:interactivity="clr-namespace:System.Windows.Interactivity;assembly=System.Windows.Interactivity">
    <TreeView ItemsSource="{Binding MyItems}" VirtualizingStackPanel.IsVirtualizing="True">
        <interactivity:Interaction.Behaviors>
            <behaviors:TreeViewSelectedItemBindingBehavior SelectedItem="{Binding SelectedItem, Mode=TwoWay}" />
        </interactivity:Interaction.Behaviors>
        <TreeView.Resources>
            <HierarchicalDataTemplate DataType="{x:Type local:MyViewModel}" ItemsSource="{Binding Children}">
                <TextBlock Text="{Binding Name}"/>
            </HierarchicalDataTemplate>
        </TreeView.Resources>
    </TreeView>
</Window>

Si puedo obtener una referencia al TreeView en el método de comportamiento adjunto OnSelectedItemChanged , tal vez pueda usar las respuestas en esta pregunta para obtener TreeViewItem pero no sé cómo llegar allí. ¿Alguien sabe cómo y es la forma correcta de ir?

Answer 1

Sé que esta es una vieja pregunta, pero tal vez será útil para otros. Combiné un código de Link

Y parece ahora:

using System.Windows;
using System.Windows.Controls;
using System.Windows.Interactivity;
using System.Windows.Media;

namespace Behaviors
{
    public class BindableSelectedItemBehavior : Behavior<TreeView>
    {
        #region SelectedItem Property

        public object SelectedItem
        {
            get { return (object)GetValue(SelectedItemProperty); }
            set { SetValue(SelectedItemProperty, value); }
        }

        public static readonly DependencyProperty SelectedItemProperty =
            DependencyProperty.Register("SelectedItem", typeof(object), typeof(BindableSelectedItemBehavior), new UIPropertyMetadata(null, OnSelectedItemChanged));

        private static void OnSelectedItemChanged(DependencyObject sender, DependencyPropertyChangedEventArgs e)
        {
            // if binded to vm collection than this way is not working
            //var item = e.NewValue as TreeViewItem;
            //if (item != null)
            //{
            //    item.SetValue(TreeViewItem.IsSelectedProperty, true);
            //}

            var tvi = e.NewValue as TreeViewItem;
            if (tvi == null)
            {
                var tree = ((BindableSelectedItemBehavior)sender).AssociatedObject;
                tvi = GetTreeViewItem(tree, e.NewValue);
            }
            if (tvi != null)
            {
                tvi.IsSelected = true;
                tvi.Focus();
            }
        }

        #endregion

        #region Private

        private void OnTreeViewSelectedItemChanged(object sender, RoutedPropertyChangedEventArgs<object> e)
        {
            SelectedItem = e.NewValue;
        }

        private static TreeViewItem GetTreeViewItem(ItemsControl container, object item)
        {
            if (container != null)
            {
                if (container.DataContext == item)
                {
                    return container as TreeViewItem;
                }

                // Expand the current container
                if (container is TreeViewItem && !((TreeViewItem)container).IsExpanded)
                {
                    container.SetValue(TreeViewItem.IsExpandedProperty, true);
                }

                // Try to generate the ItemsPresenter and the ItemsPanel.
                // by calling ApplyTemplate.  Note that in the 
                // virtualizing case even if the item is marked 
                // expanded we still need to do this step in order to 
                // regenerate the visuals because they may have been virtualized away.

                container.ApplyTemplate();
                var itemsPresenter =
                    (ItemsPresenter)container.Template.FindName("ItemsHost", container);
                if (itemsPresenter != null)
                {
                    itemsPresenter.ApplyTemplate();
                }
                else
                {
                    // The Tree template has not named the ItemsPresenter, 
                    // so walk the descendents and find the child.
                    itemsPresenter = FindVisualChild<ItemsPresenter>(container);
                    if (itemsPresenter == null)
                    {
                        container.UpdateLayout();
                        itemsPresenter = FindVisualChild<ItemsPresenter>(container);
                    }
                }

                var itemsHostPanel = (Panel)VisualTreeHelper.GetChild(itemsPresenter, 0);

                // Ensure that the generator for this panel has been created.
#pragma warning disable 168
                var children = itemsHostPanel.Children;
#pragma warning restore 168

                for (int i = 0, count = container.Items.Count; i < count; i++)
                {
                    var subContainer = (TreeViewItem)container.ItemContainerGenerator.
                                                          ContainerFromIndex(i);
                    if (subContainer == null)
                    {
                        continue;
                    }

                    subContainer.BringIntoView();

                    // Search the next level for the object.
                    var resultContainer = GetTreeViewItem(subContainer, item);
                    if (resultContainer != null)
                    {
                        return resultContainer;
                    }
                    else
                    {
                        // The object is not under this TreeViewItem
                        // so collapse it.
                        //subContainer.IsExpanded = false;
                    }
                }
            }

            return null;
        }

        /// <summary>
        /// Search for an element of a certain type in the visual tree.
        /// </summary>
        /// <typeparam name="T">The type of element to find.</typeparam>
        /// <param name="visual">The parent element.</param>
        /// <returns></returns>
        private static T FindVisualChild<T>(Visual visual) where T : Visual
        {
            for (int i = 0; i < VisualTreeHelper.GetChildrenCount(visual); i++)
            {
                Visual child = (Visual)VisualTreeHelper.GetChild(visual, i);
                if (child != null)
                {
                    T correctlyTyped = child as T;
                    if (correctlyTyped != null)
                    {
                        return correctlyTyped;
                    }

                    T descendent = FindVisualChild<T>(child);
                    if (descendent != null)
                    {
                        return descendent;
                    }
                }
            }

            return null;
        }

        #endregion

        #region Protected

        protected override void OnAttached()
        {
            base.OnAttached();

            AssociatedObject.SelectedItemChanged += OnTreeViewSelectedItemChanged;
        }

        protected override void OnDetaching()
        {
            base.OnDetaching();

            if (AssociatedObject != null)
            {
                AssociatedObject.SelectedItemChanged -= OnTreeViewSelectedItemChanged;
            }
        }

        #endregion
    }
}

Answer 2

Aquí hay una versión mejorada del comportamiento adjunto mencionado anteriormente. Admite completamente el enlace twoway y también funciona con HeriarchicalDataTemplate y TreeView s donde sus elementos están virtualizados. Sin embargo, tenga en cuenta que para encontrar el ''TreeViewItem'' que debe seleccionarse, se realizará (es decir, creará) TreeViewItem s virtualizado hasta que encuentre el correcto. Esto podría ser un problema de rendimiento con grandes árboles virtualizados.

/// <summary>
///     Behavior that makes the <see cref="System.Windows.Controls.TreeView.SelectedItem" /> bindable.
/// </summary>
public class BindableSelectedItemBehavior : Behavior<TreeView>
{
    /// <summary>
    ///     Identifies the <see cref="SelectedItem" /> dependency property.
    /// </summary>
    public static readonly DependencyProperty SelectedItemProperty =
        DependencyProperty.Register(
            "SelectedItem",
            typeof(object),
            typeof(BindableSelectedItemBehavior),
            new UIPropertyMetadata(null, OnSelectedItemChanged));

    /// <summary>
    ///     Gets or sets the selected item of the <see cref="TreeView" /> that this behavior is attached
    ///     to.
    /// </summary>
    public object SelectedItem
    {
        get
        {
            return this.GetValue(SelectedItemProperty);
        }

        set
        {
            this.SetValue(SelectedItemProperty, value);
        }
    }

    /// <summary>
    ///     Called after the behavior is attached to an AssociatedObject.
    /// </summary>
    /// <remarks>
    ///     Override this to hook up functionality to the AssociatedObject.
    /// </remarks>
    protected override void OnAttached()
    {
        base.OnAttached();
        this.AssociatedObject.SelectedItemChanged += this.OnTreeViewSelectedItemChanged;
    }

    /// <summary>
    ///     Called when the behavior is being detached from its AssociatedObject, but before it has
    ///     actually occurred.
    /// </summary>
    /// <remarks>
    ///     Override this to unhook functionality from the AssociatedObject.
    /// </remarks>
    protected override void OnDetaching()
    {
        base.OnDetaching();
        if (this.AssociatedObject != null)
        {
            this.AssociatedObject.SelectedItemChanged -= this.OnTreeViewSelectedItemChanged;
        }
    }

    private static Action<int> GetBringIndexIntoView(Panel itemsHostPanel)
    {
        var virtualizingPanel = itemsHostPanel as VirtualizingStackPanel;
        if (virtualizingPanel == null)
        {
            return null;
        }

        var method = virtualizingPanel.GetType().GetMethod(
            "BringIndexIntoView",
            BindingFlags.Instance | BindingFlags.NonPublic,
            Type.DefaultBinder,
            new[] { typeof(int) },
            null);
        if (method == null)
        {
            return null;
        }

        return i => method.Invoke(virtualizingPanel, new object[] { i });
    }

    /// <summary>
    /// Recursively search for an item in this subtree.
    /// </summary>
    /// <param name="container">
    /// The parent ItemsControl. This can be a TreeView or a TreeViewItem.
    /// </param>
    /// <param name="item">
    /// The item to search for.
    /// </param>
    /// <returns>
    /// The TreeViewItem that contains the specified item.
    /// </returns>
    private static TreeViewItem GetTreeViewItem(ItemsControl container, object item)
    {
        if (container != null)
        {
            if (container.DataContext == item)
            {
                return container as TreeViewItem;
            }

            // Expand the current container
            if (container is TreeViewItem && !((TreeViewItem)container).IsExpanded)
            {
                container.SetValue(TreeViewItem.IsExpandedProperty, true);
            }

            // Try to generate the ItemsPresenter and the ItemsPanel.
            // by calling ApplyTemplate.  Note that in the 
            // virtualizing case even if the item is marked 
            // expanded we still need to do this step in order to 
            // regenerate the visuals because they may have been virtualized away.
            container.ApplyTemplate();
            var itemsPresenter =
                (ItemsPresenter)container.Template.FindName("ItemsHost", container);
            if (itemsPresenter != null)
            {
                itemsPresenter.ApplyTemplate();
            }
            else
            {
                // The Tree template has not named the ItemsPresenter, 
                // so walk the descendents and find the child.
                itemsPresenter = container.GetVisualDescendant<ItemsPresenter>();
                if (itemsPresenter == null)
                {
                    container.UpdateLayout();
                    itemsPresenter = container.GetVisualDescendant<ItemsPresenter>();
                }
            }

            var itemsHostPanel = (Panel)VisualTreeHelper.GetChild(itemsPresenter, 0);

            // Ensure that the generator for this panel has been created.
#pragma warning disable 168
            var children = itemsHostPanel.Children;
#pragma warning restore 168

            var bringIndexIntoView = GetBringIndexIntoView(itemsHostPanel);
            for (int i = 0, count = container.Items.Count; i < count; i++)
            {
                TreeViewItem subContainer;
                if (bringIndexIntoView != null)
                {
                    // Bring the item into view so 
                    // that the container will be generated.
                    bringIndexIntoView(i);
                    subContainer =
                        (TreeViewItem)container.ItemContainerGenerator.
                                                ContainerFromIndex(i);
                }
                else
                {
                    subContainer =
                        (TreeViewItem)container.ItemContainerGenerator.
                                                ContainerFromIndex(i);

                    // Bring the item into view to maintain the 
                    // same behavior as with a virtualizing panel.
                    subContainer.BringIntoView();
                }

                if (subContainer == null)
                {
                    continue;
                }

                // Search the next level for the object.
                var resultContainer = GetTreeViewItem(subContainer, item);
                if (resultContainer != null)
                {
                    return resultContainer;
                }

                // The object is not under this TreeViewItem
                // so collapse it.
                subContainer.IsExpanded = false;
            }
        }

        return null;
    }

    private static void OnSelectedItemChanged(DependencyObject sender, DependencyPropertyChangedEventArgs e)
    {
        var item = e.NewValue as TreeViewItem;
        if (item != null)
        {
            item.SetValue(TreeViewItem.IsSelectedProperty, true);
            return;
        }

        var behavior = (BindableSelectedItemBehavior)sender;
        var treeView = behavior.AssociatedObject;
        if (treeView == null)
        {
            // at designtime the AssociatedObject sometimes seems to be null
            return;
        }

        item = GetTreeViewItem(treeView, e.NewValue);
        if (item != null)
        {
            item.IsSelected = true;
        }
    }

    private void OnTreeViewSelectedItemChanged(object sender, RoutedPropertyChangedEventArgs<object> e)
    {
        this.SelectedItem = e.NewValue;
    }
}

Y en aras de la integridad, aquí está la implementación de GetVisualDescentants :

/// <summary>
///     Extension methods for the <see cref="DependencyObject" /> type.
/// </summary>
public static class DependencyObjectExtensions
{
    /// <summary>
    ///     Gets the first child of the specified visual that is of tyoe <typeparamref name="T" />
    ///     in the visual tree recursively.
    /// </summary>
    /// <param name="visual">The visual to get the visual children for.</param>
    /// <returns>
    ///     The first child of the specified visual that is of tyoe <typeparamref name="T" /> of the
    ///     specified visual in the visual tree recursively or <c>null</c> if none was found.
    /// </returns>
    public static T GetVisualDescendant<T>(this DependencyObject visual) where T : DependencyObject
    {
        return (T)visual.GetVisualDescendants().FirstOrDefault(d => d is T);
    }

    /// <summary>
    ///     Gets all children of the specified visual in the visual tree recursively.
    /// </summary>
    /// <param name="visual">The visual to get the visual children for.</param>
    /// <returns>All children of the specified visual in the visual tree recursively.</returns>
    public static IEnumerable<DependencyObject> GetVisualDescendants(this DependencyObject visual)
    {
        if (visual == null)
        {
            yield break;
        }

        for (var i = 0; i < VisualTreeHelper.GetChildrenCount(visual); i++)
        {
            var child = VisualTreeHelper.GetChild(visual, i);
            yield return child;
            foreach (var subChild in GetVisualDescendants(child))
            {
                yield return subChild;
            }
        }
    }
}

Answer 3

Si encuentra, como yo lo hice, que esta respuesta a veces falla porque itemPresenter es nulo, entonces esta modificación a esa solución podría funcionar para usted.

Cambie OnSelectedItemChanged a esto (si el Árbol aún no está cargado, espera hasta que se cargue el Árbol y lo intenta de nuevo):

private static void OnSelectedItemChanged(DependencyObject sender, DependencyPropertyChangedEventArgs e)
{
    Action<TreeViewItem> selectTreeViewItem = tvi2 =>
    {
        if (tvi2 != null)
        {
            tvi2.IsSelected = true;
            tvi2.Focus();
        }
    };

    var tvi = e.NewValue as TreeViewItem;

    if (tvi == null)
    {
        var tree = ((BindableTreeViewSelectedItemBehavior) sender).AssociatedObject;
        if (!tree.IsLoaded)
        {
            RoutedEventHandler handler = null;
            handler = (sender2, e2) =>
            {
                tvi = GetTreeViewItem(tree, e.NewValue);
                selectTreeViewItem(tvi);
                tree.Loaded -= handler;
            };
            tree.Loaded += handler;

            return;
        }
        tvi = GetTreeViewItem(tree, e.NewValue);
    }

    selectTreeViewItem(tvi);
}