我可能正在经历周一的迟钝，但我找不到一种不错的方法，在我在代码后台添加了所有treeview节点之后，展开它们（类似于treeView.ExpandAll()）。
有什么快速的帮助吗？
5个回答
32
XAML 中可以这样做：
<TreeView.ItemContainerStyle>
<Style TargetType="TreeViewItem">
<Setter Property="TreeViewItem.IsExpanded" Value="True"/>
</Style>
</TreeView.ItemContainerStyle>
- OrPaz
7
在尝试了所有完全展开和折叠树形视图的各种方法后，迄今为止最快的方法是以下方法。这种方法似乎适用于非常大的树。
确保您的树是虚拟化的，如果它没有被虚拟化，那么一旦树达到任何规模，无论您做什么，它都会变得非常缓慢。
VirtualizingStackPanel.IsVirtualizing="True"
VirtualizingStackPanel.VirtualizationMode="Recycling"
假设您有一个视图模型来支持树形结构，每个对应于
HierarchicalDataTemplate 的视图模型节点都需要一个 IsExpanded 属性（它不需要实现属性更改）。假设这些视图模型实现了以下接口：interface IExpandableItem : IEnumerable
{
bool IsExpanded { get; set; }
}
为了将视图模型中的IsExpanded属性绑定到视图，需要将TreeViewItem样式设置如下：
<Style
TargetType="{x:Type TreeViewItem}">
<Setter
Property="IsExpanded"
Value="{Binding
IsExpanded,
Mode=TwoWay}" />
</Style>
我们将使用这个属性来设置展开状态，而且，由于树是虚拟化的，这个属性对于在节点被回收时保持正确的视图状态是必要的。如果没有绑定这个属性，在用户浏览树时，节点会因为超出视图范围而被折叠。
实现大型树的可接受速度的唯一方法是在视图层中使用后台代码。计划基本上如下：
1. 获取当前绑定到 TreeView.ItemsSource 的绑定。 2. 清除该绑定。 3. 等待绑定实际清除。 4. 在（现在未绑定的）视图模型中设置展开状态。 5. 使用我们在第1步中缓存的绑定重新绑定 TreeView.ItemsSource。
因为我们启用了虚拟化，在 TreeView.ItemsSource 上执行绑定实际上非常快，即使有一个大的视图模型。同样，在解除绑定时更新节点的展开状态应该非常快。这导致更新非常快。
以下是一些代码：
void SetExpandedStateInView(bool isExpanded)
{
var model = this.DataContext as TreeViewModel;
if (model == null)
{
// View model is not bound so do nothing.
return;
}
// Grab hold of the current ItemsSource binding.
var bindingExpression = this.TreeView.GetBindingExpression(
ItemsControl.ItemsSourceProperty);
if (bindingExpression == null)
{
return;
}
// Clear that binding.
var itemsSourceBinding = bindingExpression.ParentBinding;
BindingOperations.ClearBinding(
this.TreeView, ItemsControl.ItemsSourceProperty);
// Wait for the binding to clear and then set the expanded state of the view model.
this.Dispatcher.BeginInvoke(
DispatcherPriority.DataBind,
new Action(() => SetExpandedStateInModel(model.Items, isExpanded)));
// Now rebind the ItemsSource.
this.Dispatcher.BeginInvoke(
DispatcherPriority.DataBind,
new Action(
() => this.TreeView.SetBinding(
ItemsControl.ItemsSourceProperty, itemsSourceBinding)));
}
void SetExpandedStateInModel(IEnumerable modelItems, bool isExpanded)
{
if (modelItems == null)
{
return;
}
foreach (var modelItem in modelItems)
{
var expandable = modelItem as IExpandableItem;
if (expandable == null)
{
continue;
}
expandable.IsExpanded = isExpanded;
SetExpandedStateInModel(expandable, isExpanded);
}
}
- satnhak
1
1真正的生活救星！ - edtheprogrammerguy
0
我已经完成了一个ExpandAll，它也适用于树设置为虚拟化（回收项）的情况。
这是我的代码。也许你应该考虑将你的层次结构包装成分层模型视图？
using System;
using System.Collections;
using System.Collections.Generic;
using System.Diagnostics;
using System.Windows.Controls;
using System.Windows.Controls.Primitives;
using System.Windows.Threading;
using HQ.Util.General;
namespace HQ.Util.Wpf.WpfUtil
{
public static class TreeViewExtensions
{
// ******************************************************************
public delegate void OnTreeViewVisible(TreeViewItem tvi);
public delegate void OnItemExpanded(TreeViewItem tvi, object item);
public delegate void OnAllItemExpanded();
// ******************************************************************
private static void SetItemHierarchyVisible(ItemContainerGenerator icg, IList listOfRootToNodeItemPath, OnTreeViewVisible onTreeViewVisible = null)
{
Debug.Assert(icg != null);
if (icg != null)
{
if (listOfRootToNodeItemPath.Count == 0) // nothing to do
return;
TreeViewItem tvi = icg.ContainerFromItem(listOfRootToNodeItemPath[0]) as TreeViewItem;
if (tvi != null) // Due to threading, always better to verify
{
listOfRootToNodeItemPath.RemoveAt(0);
if (listOfRootToNodeItemPath.Count == 0)
{
if (onTreeViewVisible != null)
onTreeViewVisible(tvi);
}
else
{
if (!tvi.IsExpanded)
tvi.IsExpanded = true;
SetItemHierarchyVisible(tvi.ItemContainerGenerator, listOfRootToNodeItemPath, onTreeViewVisible);
}
}
else
{
ActionHolder actionHolder = new ActionHolder();
EventHandler itemCreated = delegate(object sender, EventArgs eventArgs)
{
var icgSender = sender as ItemContainerGenerator;
tvi = icgSender.ContainerFromItem(listOfRootToNodeItemPath[0]) as TreeViewItem;
if (tvi != null) // Due to threading, it is always better to verify
{
SetItemHierarchyVisible(icg, listOfRootToNodeItemPath, onTreeViewVisible);
actionHolder.Execute();
}
};
actionHolder.Action = new Action(() => icg.StatusChanged -= itemCreated);
icg.StatusChanged += itemCreated;
return;
}
}
}
// ******************************************************************
/// <summary>
/// You cannot rely on this method to be synchronous. If you have any action that depend on the TreeViewItem
/// (last item of collectionOfRootToNodePath) to be visible, you should set it in the 'onTreeViewItemVisible' method.
/// This method should work for Virtualized and non virtualized tree.
/// The difference with ExpandItem is that this one open up the tree up to the target but will not expand the target itself,
/// while ExpandItem expand the target itself.
/// </summary>
/// <param name="treeView">TreeView where an item has to be set visible</param>
/// <param name="listOfRootToNodePath">Any collectionic List. The collection should have every objet of the path to the targeted item from the root
/// to the target. For example for an apple tree: AppleTree (index 0), Branch4, SubBranch3, Leaf2 (index 3)</param>
/// <param name="onTreeViewVisible">Optionnal</param>
public static void SetItemHierarchyVisible(this TreeView treeView, IEnumerable<object> listOfRootToNodePath, OnTreeViewVisible onTreeViewVisible = null)
{
ItemContainerGenerator icg = treeView.ItemContainerGenerator;
if (icg == null)
return; // Is tree loaded and initialized ???
SetItemHierarchyVisible(icg, new List<object>(listOfRootToNodePath), onTreeViewVisible);
}
// ******************************************************************
private static void ExpandItem(ItemContainerGenerator icg, IList listOfRootToNodePath, OnTreeViewVisible onTreeViewVisible = null)
{
Debug.Assert(icg != null);
if (icg != null)
{
if (listOfRootToNodePath.Count == 0) // nothing to do
return;
TreeViewItem tvi = icg.ContainerFromItem(listOfRootToNodePath[0]) as TreeViewItem;
if (tvi != null) // Due to threading, always better to verify
{
listOfRootToNodePath.RemoveAt(0);
if (!tvi.IsExpanded)
tvi.IsExpanded = true;
if (listOfRootToNodePath.Count == 0)
{
if (onTreeViewVisible != null)
onTreeViewVisible(tvi);
}
else
{
SetItemHierarchyVisible(tvi.ItemContainerGenerator, listOfRootToNodePath, onTreeViewVisible);
}
}
else
{
ActionHolder actionHolder = new ActionHolder();
EventHandler itemCreated = delegate(object sender, EventArgs eventArgs)
{
var icgSender = sender as ItemContainerGenerator;
tvi = icgSender.ContainerFromItem(listOfRootToNodePath[0]) as TreeViewItem;
if (tvi != null) // Due to threading, it is always better to verify
{
SetItemHierarchyVisible(icg, listOfRootToNodePath, onTreeViewVisible);
actionHolder.Execute();
}
};
actionHolder.Action = new Action(() => icg.StatusChanged -= itemCreated);
icg.StatusChanged += itemCreated;
return;
}
}
}
// ******************************************************************
/// <summary>
/// You cannot rely on this method to be synchronous. If you have any action that depend on the TreeViewItem
/// (last item of collectionOfRootToNodePath) to be visible, you should set it in the 'onTreeViewItemVisible' method.
/// This method should work for Virtualized and non virtualized tree.
/// The difference with SetItemHierarchyVisible is that this one open the target while SetItemHierarchyVisible does not try to expand the target.
/// (SetItemHierarchyVisible just ensure the target will be visible)
/// </summary>
/// <param name="treeView">TreeView where an item has to be set visible</param>
/// <param name="listOfRootToNodePath">The collection should have every objet of the path, from the root to the targeted item.
/// For example for an apple tree: AppleTree (index 0), Branch4, SubBranch3, Leaf2</param>
/// <param name="onTreeViewVisible">Optionnal</param>
public static void ExpandItem(this TreeView treeView, IEnumerable<object> listOfRootToNodePath, OnTreeViewVisible onTreeViewVisible = null)
{
ItemContainerGenerator icg = treeView.ItemContainerGenerator;
if (icg == null)
return; // Is tree loaded and initialized ???
ExpandItem(icg, new List<object>(listOfRootToNodePath), onTreeViewVisible);
}
// ******************************************************************
private static void ExpandSubWithContainersGenerated(ItemsControl ic, Action<TreeViewItem, object> actionItemExpanded, ReferenceCounterTracker referenceCounterTracker)
{
ItemContainerGenerator icg = ic.ItemContainerGenerator;
foreach (object item in ic.Items)
{
var tvi = icg.ContainerFromItem(item) as TreeViewItem;
actionItemExpanded(tvi, item);
tvi.IsExpanded = true;
ExpandSubContainers(tvi, actionItemExpanded, referenceCounterTracker);
}
}
// ******************************************************************
/// <summary>
/// Expand any ItemsControl (TreeView, TreeViewItem, ListBox, ComboBox, ...) and their childs if any (TreeView)
/// </summary>
/// <param name="ic"></param>
/// <param name="actionItemExpanded"></param>
/// <param name="referenceCounterTracker"></param>
public static void ExpandSubContainers(ItemsControl ic, Action<TreeViewItem, object> actionItemExpanded, ReferenceCounterTracker referenceCounterTracker)
{
ItemContainerGenerator icg = ic.ItemContainerGenerator;
{
if (icg.Status == GeneratorStatus.ContainersGenerated)
{
ExpandSubWithContainersGenerated(ic, actionItemExpanded, referenceCounterTracker);
}
else if (icg.Status == GeneratorStatus.NotStarted)
{
ActionHolder actionHolder = new ActionHolder();
EventHandler itemCreated = delegate(object sender, EventArgs eventArgs)
{
var icgSender = sender as ItemContainerGenerator;
if (icgSender.Status == GeneratorStatus.ContainersGenerated)
{
ExpandSubWithContainersGenerated(ic, actionItemExpanded, referenceCounterTracker);
// Never use the following method in BeginInvoke due to ICG recycling. The same icg could be
// used and will keep more than one subscribers which is far from being intended
// ic.Dispatcher.BeginInvoke(actionHolder.Action, DispatcherPriority.Background);
// Very important to unsubscribe as soon we've done due to ICG recycling.
actionHolder.Execute();
referenceCounterTracker.ReleaseRef();
}
};
referenceCounterTracker.AddRef();
actionHolder.Action = new Action(() => icg.StatusChanged -= itemCreated);
icg.StatusChanged += itemCreated;
// Next block is only intended to protect against any race condition (I don't know if it is possible ? How Microsoft implemented it)
// I mean the status changed before I subscribe to StatusChanged but after I made the check about its state.
if (icg.Status == GeneratorStatus.ContainersGenerated)
{
ExpandSubWithContainersGenerated(ic, actionItemExpanded, referenceCounterTracker);
}
}
}
}
// ******************************************************************
/// <summary>
/// This method is asynchronous.
/// Expand all items and subs recursively if any. Does support virtualization (item recycling).
/// But honestly, make you a favor, make your life easier en create a model view around your hierarchy with
/// a IsExpanded property for each node level and bind it to each TreeView node level.
/// </summary>
/// <param name="treeView"></param>
/// <param name="actionItemExpanded"></param>
/// <param name="actionAllItemExpanded"></param>
public static void ExpandAll(this TreeView treeView, Action<TreeViewItem, object> actionItemExpanded = null, Action actionAllItemExpanded = null)
{
var referenceCounterTracker = new ReferenceCounterTracker(actionAllItemExpanded);
referenceCounterTracker.AddRef();
treeView.Dispatcher.BeginInvoke(new Action(() => ExpandSubContainers(treeView, actionItemExpanded, referenceCounterTracker)), DispatcherPriority.Background);
referenceCounterTracker.ReleaseRef();
}
// ******************************************************************
}
}
而且
using System;
using System.Threading;
namespace HQ.Util.General
{
public class ReferenceCounterTracker
{
private Action _actionOnCountReachZero = null;
private int _count = 0;
public ReferenceCounterTracker(Action actionOnCountReachZero)
{
_actionOnCountReachZero = actionOnCountReachZero;
}
public void AddRef()
{
Interlocked.Increment(ref _count);
}
public void ReleaseRef()
{
int count = Interlocked.Decrement(ref _count);
if (count == 0)
{
if (_actionOnCountReachZero != null)
{
_actionOnCountReachZero();
}
}
}
}
}
- Eric Ouellet
0
您需要在您的项目中包含以下方法：
private void ExpandAllNodes(TreeViewItem treeItem)
{
treeItem.IsExpanded = true;
foreach (var childItem in treeItem.Items.OfType<TreeViewItem>())
{
ExpandAllNodes(childItem);
}
}
那么，您只需要像这样调用它：
treeView.Items.OfType<TreeViewItem>().ToList().ForEach(ExpandAllNodes);
- Ricardo Almeida
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