我可能会遇到星期一的愚蠢，但是在我将它们添加到后面的代码中后，我找不到扩展所有树视图节点的好方法（类似于treeView.ExpandAll（））。
任何快速帮助？
答案 0 :(得分：29)
在xaml中你可以这样做：
<TreeView.ItemContainerStyle>
<Style TargetType="TreeViewItem">
<Setter Property="TreeViewItem.IsExpanded" Value="True"/>
</Style>
</TreeView.ItemContainerStyle>
答案 1 :(得分：4)
在使用完全展开和折叠树视图的所有各种方法之后，到目前为止最快的方法如下。这种方法似乎适用于非常大的树木。
确保您的树是虚拟化的，如果它没有被虚拟化，那么只要树达到任何类型的大小，无论您做什么，它都会变得非常缓慢。
VirtualizingStackPanel.IsVirtualizing="True"
VirtualizingStackPanel.VirtualizationMode="Recycling"
假设您有一个支持树的视图模型，该视图模型上与HierarchicalDataTemplate对应的每个节点都需要一个IsExpanded属性（它不需要实现属性更改） 。假设这些视图模型实现了这样的接口：
interface IExpandableItem : IEnumerable
{
bool IsExpanded { get; set; }
}
需要按如下方式设置TreeViewItem样式，以便将视图模型中的IsExpanded属性绑定到视图：
<Style
TargetType="{x:Type TreeViewItem}">
<Setter
Property="IsExpanded"
Value="{Binding
IsExpanded,
Mode=TwoWay}" />
</Style>
我们将使用此属性来设置扩展状态，但是，因为树是虚拟化的，所以此属性对于维持正确的视图状态是必要的，因为单个TreeViewItem被回收。如果没有这个绑定节点，当用户浏览树时，节点将会退出视图。
在大树上获得可接受速度的唯一方法是在视图层中使用代码。该计划基本如下：
TreeView.ItemsSource。TreeView.ItemsSource。由于我们启用了虚拟化，因此即使使用大型视图模型，在TreeView.ItemsSource上执行绑定也会非常快。同样，当未绑定更新节点的扩展状态时应该非常快。这导致令人惊讶的快速更新。
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);
}
}
答案 2 :(得分：2)
WPF没有ExpandAll方法。您需要循环并在每个节点上设置属性。
答案 3 :(得分：0)
如果您的树设置为虚拟化（回收项目），我已经完成了一个ExpandAll。
这是我的代码。也许您应该考虑将层次结构包装到层次模型模型视图中？
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();
}
// ******************************************************************
}
}
和
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();
}
}
}
}
}
答案 4 :(得分：0)
您必须在项目中包括以下方法：
private void ExpandAllNodes(TreeViewItem treeItem)
{
treeItem.IsExpanded = true;
foreach (var childItem in treeItem.Items.OfType<TreeViewItem>())
{
ExpandAllNodes(childItem);
}
}
然后，您只需要这样称呼它即可：
treeView.Items.OfType<TreeViewItem>().ToList().ForEach(ExpandAllNodes);