लिंक Estifanos किडेन दिया टूट गया है निर्धारित किया है। वह शायद the "Changing selection in a virtualized TreeView" MSDN sample था। हालांकि, यह नमूना दिखाता है कि एक पेड़ में नोड का चयन कैसे करें, लेकिन कोड-बैक का उपयोग करके और एमवीवीएम और बाध्यकारी नहीं, इसलिए यह लापता SelectedItemChanged event को बाध्य नहीं करता है जब बाएं चयनित इटैम बदल जाता है।
एकमात्र समाधान जो मैं सोच सकता हूं वह एमवीवीएम पैटर्न को तोड़ना है, और जब व्यूमोडेल प्रॉपर्टी जो चयनित इटैम संपत्ति परिवर्तन से जुड़ी हुई है, तो देखें और कोड-बैक विधि (एमएसडीएन नमूना के समान) को कॉल करें सुनिश्चित करें कि पेड़ में वास्तव में नया मूल्य चुना गया है।
यहाँ कोड मैं इसे संभाल करने के लिए लिखा है। मान लीजिए कि आपके डेटा आइटम प्रकार Node जो एक Parent संपत्ति है के होते हैं:
public class Node
{
public Node Parent { get; set; }
}
मैं निम्नलिखित व्यवहार वर्ग ने लिखा है:
using System;
using System.Collections.Generic;
using System.Diagnostics;
using System.Reflection;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Interactivity;
public class NodeTreeSelectionBehavior : Behavior<TreeView>
{
public Node SelectedItem
{
get { return (Node)GetValue(SelectedItemProperty); }
set { SetValue(SelectedItemProperty, value); }
}
public static readonly DependencyProperty SelectedItemProperty =
DependencyProperty.Register("SelectedItem", typeof(Node), typeof(NodeTreeSelectionBehavior),
new FrameworkPropertyMetadata(null, FrameworkPropertyMetadataOptions.BindsTwoWayByDefault, OnSelectedItemChanged));
private static void OnSelectedItemChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
{
var newNode = e.NewValue as Node;
if (newNode == null) return;
var behavior = (NodeTreeSelectionBehavior)d;
var tree = behavior.AssociatedObject;
var nodeDynasty = new List<Node> { newNode };
var parent = newNode.Parent;
while (parent != null)
{
nodeDynasty.Insert(0, parent);
parent = parent.Parent;
}
var currentParent = tree as ItemsControl;
foreach (var node in nodeDynasty)
{
// first try the easy way
var newParent = currentParent.ItemContainerGenerator.ContainerFromItem(node) as TreeViewItem;
if (newParent == null)
{
// if this failed, it's probably because of virtualization, and we will have to do it the hard way.
// this code is influenced by TreeViewItem.ExpandRecursive decompiled code, and the MSDN sample at http://code.msdn.microsoft.com/Changing-selection-in-a-6a6242c8/sourcecode?fileId=18862&pathId=753647475
// see also the question at http://stackoverflow.com/q/183636/46635
currentParent.ApplyTemplate();
var itemsPresenter = (ItemsPresenter)currentParent.Template.FindName("ItemsHost", currentParent);
if (itemsPresenter != null)
{
itemsPresenter.ApplyTemplate();
}
else
{
currentParent.UpdateLayout();
}
var virtualizingPanel = GetItemsHost(currentParent) as VirtualizingPanel;
CallEnsureGenerator(virtualizingPanel);
var index = currentParent.Items.IndexOf(node);
if (index < 0)
{
throw new InvalidOperationException("Node '" + node + "' cannot be fount in container");
}
CallBringIndexIntoView(virtualizingPanel, index);
newParent = currentParent.ItemContainerGenerator.ContainerFromIndex(index) as TreeViewItem;
}
if (newParent == null)
{
throw new InvalidOperationException("Tree view item cannot be found or created for node '" + node + "'");
}
if (node == newNode)
{
newParent.IsSelected = true;
newParent.BringIntoView();
break;
}
newParent.IsExpanded = true;
currentParent = newParent;
}
}
protected override void OnAttached()
{
base.OnAttached();
AssociatedObject.SelectedItemChanged += OnTreeViewSelectedItemChanged;
}
protected override void OnDetaching()
{
base.OnDetaching();
AssociatedObject.SelectedItemChanged -= OnTreeViewSelectedItemChanged;
}
private void OnTreeViewSelectedItemChanged(object sender, RoutedPropertyChangedEventArgs<object> e)
{
SelectedItem = e.NewValue as Node;
}
#region Functions to get internal members using reflection
// Some functionality we need is hidden in internal members, so we use reflection to get them
#region ItemsControl.ItemsHost
static readonly PropertyInfo ItemsHostPropertyInfo = typeof(ItemsControl).GetProperty("ItemsHost", BindingFlags.Instance | BindingFlags.NonPublic);
private static Panel GetItemsHost(ItemsControl itemsControl)
{
Debug.Assert(itemsControl != null);
return ItemsHostPropertyInfo.GetValue(itemsControl, null) as Panel;
}
#endregion ItemsControl.ItemsHost
#region Panel.EnsureGenerator
private static readonly MethodInfo EnsureGeneratorMethodInfo = typeof(Panel).GetMethod("EnsureGenerator", BindingFlags.Instance | BindingFlags.NonPublic);
private static void CallEnsureGenerator(Panel panel)
{
Debug.Assert(panel != null);
EnsureGeneratorMethodInfo.Invoke(panel, null);
}
#endregion Panel.EnsureGenerator
#region VirtualizingPanel.BringIndexIntoView
private static readonly MethodInfo BringIndexIntoViewMethodInfo = typeof(VirtualizingPanel).GetMethod("BringIndexIntoView", BindingFlags.Instance | BindingFlags.NonPublic);
private static void CallBringIndexIntoView(VirtualizingPanel virtualizingPanel, int index)
{
Debug.Assert(virtualizingPanel != null);
BringIndexIntoViewMethodInfo.Invoke(virtualizingPanel, new object[] { index });
}
#endregion VirtualizingPanel.BringIndexIntoView
#endregion Functions to get internal members using reflection
}
इस वर्ग के साथ, आप निम्नलिखित की तरह XAML लिख सकते हैं:
<UserControl xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:i="clr-namespace:System.Windows.Interactivity;assembly=System.Windows.Interactivity"
xmlns:local="clr-namespace:MyProject">
<Grid>
<TreeView ItemsSource="{Binding MyItems}"
ScrollViewer.CanContentScroll="True"
VirtualizingStackPanel.IsVirtualizing="True"
VirtualizingStackPanel.VirtualizationMode="Recycling">
<i:Interaction.Behaviors>
<local:NodeTreeSelectionBehavior SelectedItem="{Binding MySelectedItem}" />
</i:Interaction.Behaviors>
</TreeView>
<Grid>
<UserControl>
हाय, मैं भी एक ही मुद्दे के साथ अटक कर रहा हूँ। आपको इस समस्या का कोई समाधान मिला है? – akjoshi