如何检索在WPF-treeview中选择的项?我想在XAML中这样做，因为我想绑定它。
您可能认为它是SelectedItem，但显然它不存在是只读的，因此不可用。
这就是我想做的:
<TreeView ItemsSource="{Binding Path=Model.Clusters}"
ItemTemplate="{StaticResource ClusterTemplate}"
SelectedItem="{Binding Path=Model.SelectedCluster}" />
我想将SelectedItem绑定到我的Model上的一个属性。
但这给了我一个错误:
“SelectedItem”属性是只读的，不能从标记中设置。
编辑:
这就是我解决这个问题的方法:
<TreeView
ItemsSource="{Binding Path=Model.Clusters}"
ItemTemplate="{StaticResource HoofdCLusterTemplate}"
SelectedItemChanged="TreeView_OnSelectedItemChanged" />
在我的xaml的代码背后文件:
private void TreeView_OnSelectedItemChanged(object sender, RoutedPropertyChangedEventArgs<object> e)
{
Model.SelectedCluster = (Cluster)e.NewValue;
}
还有一种方法可以在不使用Interaction.Behaviors的情况下创建XAML可绑定SelectedItem属性。
public static class BindableSelectedItemHelper
{
#region Properties
public static readonly DependencyProperty SelectedItemProperty = DependencyProperty.RegisterAttached("SelectedItem", typeof(object), typeof(BindableSelectedItemHelper),
new FrameworkPropertyMetadata(null, OnSelectedItemPropertyChanged));
public static readonly DependencyProperty AttachProperty = DependencyProperty.RegisterAttached("Attach", typeof(bool), typeof(BindableSelectedItemHelper), new PropertyMetadata(false, Attach));
private static readonly DependencyProperty IsUpdatingProperty = DependencyProperty.RegisterAttached("IsUpdating", typeof(bool), typeof(BindableSelectedItemHelper));
#endregion
#region Implementation
public static void SetAttach(DependencyObject dp, bool value)
{
dp.SetValue(AttachProperty, value);
}
public static bool GetAttach(DependencyObject dp)
{
return (bool)dp.GetValue(AttachProperty);
}
public static string GetSelectedItem(DependencyObject dp)
{
return (string)dp.GetValue(SelectedItemProperty);
}
public static void SetSelectedItem(DependencyObject dp, object value)
{
dp.SetValue(SelectedItemProperty, value);
}
private static bool GetIsUpdating(DependencyObject dp)
{
return (bool)dp.GetValue(IsUpdatingProperty);
}
private static void SetIsUpdating(DependencyObject dp, bool value)
{
dp.SetValue(IsUpdatingProperty, value);
}
private static void Attach(DependencyObject sender, DependencyPropertyChangedEventArgs e)
{
TreeListView treeListView = sender as TreeListView;
if (treeListView != null)
{
if ((bool)e.OldValue)
treeListView.SelectedItemChanged -= SelectedItemChanged;
if ((bool)e.NewValue)
treeListView.SelectedItemChanged += SelectedItemChanged;
}
}
private static void OnSelectedItemPropertyChanged(DependencyObject sender, DependencyPropertyChangedEventArgs e)
{
TreeListView treeListView = sender as TreeListView;
if (treeListView != null)
{
treeListView.SelectedItemChanged -= SelectedItemChanged;
if (!(bool)GetIsUpdating(treeListView))
{
foreach (TreeViewItem item in treeListView.Items)
{
if (item == e.NewValue)
{
item.IsSelected = true;
break;
}
else
item.IsSelected = false;
}
}
treeListView.SelectedItemChanged += SelectedItemChanged;
}
}
private static void SelectedItemChanged(object sender, RoutedEventArgs e)
{
TreeListView treeListView = sender as TreeListView;
if (treeListView != null)
{
SetIsUpdating(treeListView, true);
SetSelectedItem(treeListView, treeListView.SelectedItem);
SetIsUpdating(treeListView, false);
}
}
#endregion
}
然后你可以在你的XAML中使用它:
<TreeView helper:BindableSelectedItemHelper.Attach="True"
helper:BindableSelectedItemHelper.SelectedItem="{Binding SelectedItem, Mode=TwoWay}">
我的需求是基于PRISM-MVVM的解决方案，其中需要TreeView，绑定对象类型为Collection<>，因此需要HierarchicalDataTemplate。默认的BindableSelectedItemBehavior不能识别子TreeViewItem。让它在这种情况下起作用。
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)
{
var behavior = sender as BindableSelectedItemBehavior;
if (behavior == null) return;
var tree = behavior.AssociatedObject;
if (tree == null) return;
if (e.NewValue == null)
foreach (var item in tree.Items.OfType<TreeViewItem>())
item.SetValue(TreeViewItem.IsSelectedProperty, false);
var treeViewItem = e.NewValue as TreeViewItem;
if (treeViewItem != null)
treeViewItem.SetValue(TreeViewItem.IsSelectedProperty, true);
else
{
var itemsHostProperty = tree.GetType().GetProperty("ItemsHost", System.Reflection.BindingFlags.NonPublic | System.Reflection.BindingFlags.Instance);
if (itemsHostProperty == null) return;
var itemsHost = itemsHostProperty.GetValue(tree, null) as Panel;
if (itemsHost == null) return;
foreach (var item in itemsHost.Children.OfType<TreeViewItem>())
{
if (WalkTreeViewItem(item, e.NewValue))
break;
}
}
}
public static bool WalkTreeViewItem(TreeViewItem treeViewItem, object selectedValue)
{
if (treeViewItem.DataContext == selectedValue)
{
treeViewItem.SetValue(TreeViewItem.IsSelectedProperty, true);
treeViewItem.Focus();
return true;
}
var itemsHostProperty = treeViewItem.GetType().GetProperty("ItemsHost", System.Reflection.BindingFlags.NonPublic | System.Reflection.BindingFlags.Instance);
if (itemsHostProperty == null) return false;
var itemsHost = itemsHostProperty.GetValue(treeViewItem, null) as Panel;
if (itemsHost == null) return false;
foreach (var item in itemsHost.Children.OfType<TreeViewItem>())
{
if (WalkTreeViewItem(item, selectedValue))
break;
}
return false;
}
#endregion
protected override void OnAttached()
{
base.OnAttached();
this.AssociatedObject.SelectedItemChanged += OnTreeViewSelectedItemChanged;
}
protected override void OnDetaching()
{
base.OnDetaching();
if (this.AssociatedObject != null)
{
this.AssociatedObject.SelectedItemChanged -= OnTreeViewSelectedItemChanged;
}
}
private void OnTreeViewSelectedItemChanged(object sender, RoutedPropertyChangedEventArgs<object> e)
{
this.SelectedItem = e.NewValue;
}
}
这样就可以遍历所有元素，而不考虑级别。
这可以以一种“更好”的方式完成，只使用绑定和GalaSoft MVVM Light库的EventToCommand。在您的VM中添加一个命令，当所选项目发生变化时将调用该命令，并初始化该命令以执行任何必要的操作。在这个例子中，我使用了一个RelayCommand，只设置SelectedCluster属性。
public class ViewModel
{
public ViewModel()
{
SelectedClusterChanged = new RelayCommand<Cluster>( c => SelectedCluster = c );
}
public RelayCommand<Cluster> SelectedClusterChanged { get; private set; }
public Cluster SelectedCluster { get; private set; }
}
然后在xaml中添加EventToCommand行为。使用混合非常简单。
<TreeView
x:Name="lstClusters"
ItemsSource="{Binding Path=Model.Clusters}"
ItemTemplate="{StaticResource HoofdCLusterTemplate}">
<i:Interaction.Triggers>
<i:EventTrigger EventName="SelectedItemChanged">
<GalaSoft_MvvmLight_Command:EventToCommand Command="{Binding SelectedClusterChanged}" CommandParameter="{Binding ElementName=lstClusters,Path=SelectedValue}"/>
</i:EventTrigger>
</i:Interaction.Triggers>
</TreeView>
我给你带来了我的解决方案，它具有以下特点:
支持2种绑定方式
自动更新TreeViewItemIsSelected属性(根据SelectedItem)
没有TreeView子类
绑定到ViewModel的项可以是任何类型(甚至是null)
1/在你的CS中粘贴以下代码:
public class BindableSelectedItem
{
public static readonly DependencyProperty SelectedItemProperty = DependencyProperty.RegisterAttached(
"SelectedItem", typeof(object), typeof(BindableSelectedItem), new PropertyMetadata(default(object), OnSelectedItemPropertyChangedCallback));
private static void OnSelectedItemPropertyChangedCallback(DependencyObject d, DependencyPropertyChangedEventArgs e)
{
var treeView = d as TreeView;
if (treeView != null)
{
BrowseTreeViewItems(treeView, tvi =>
{
tvi.IsSelected = tvi.DataContext == e.NewValue;
});
}
else
{
throw new Exception("Attached property supports only TreeView");
}
}
public static void SetSelectedItem(DependencyObject element, object value)
{
element.SetValue(SelectedItemProperty, value);
}
public static object GetSelectedItem(DependencyObject element)
{
return element.GetValue(SelectedItemProperty);
}
public static void BrowseTreeViewItems(TreeView treeView, Action<TreeViewItem> onBrowsedTreeViewItem)
{
var collectionsToVisit = new System.Collections.Generic.List<Tuple<ItemContainerGenerator, ItemCollection>> { new Tuple<ItemContainerGenerator, ItemCollection>(treeView.ItemContainerGenerator, treeView.Items) };
var collectionIndex = 0;
while (collectionIndex < collectionsToVisit.Count)
{
var itemContainerGenerator = collectionsToVisit[collectionIndex].Item1;
var itemCollection = collectionsToVisit[collectionIndex].Item2;
for (var i = 0; i < itemCollection.Count; i++)
{
var tvi = itemContainerGenerator.ContainerFromIndex(i) as TreeViewItem;
if (tvi == null)
{
continue;
}
if (tvi.ItemContainerGenerator.Status == System.Windows.Controls.Primitives.GeneratorStatus.ContainersGenerated)
{
collectionsToVisit.Add(new Tuple<ItemContainerGenerator, ItemCollection>(tvi.ItemContainerGenerator, tvi.Items));
}
onBrowsedTreeViewItem(tvi);
}
collectionIndex++;
}
}
}
2/在XAML文件中使用的例子
<TreeView myNS:BindableSelectedItem.SelectedItem="{Binding Path=SelectedItem, Mode=TwoWay}" />
(让我们都同意，TreeView在这个问题上显然是行不通的。绑定到SelectedItem是显而易见的。叹息)
我需要解决方案来正确地与TreeViewItem的IsSelected属性交互，所以这是我是如何做到的:
// the Type CustomThing needs to implement IsSelected with notification
// for this to work.
public class CustomTreeView : TreeView
{
public CustomThing SelectedCustomThing
{
get
{
return (CustomThing)GetValue(SelectedNode_Property);
}
set
{
SetValue(SelectedNode_Property, value);
if(value != null) value.IsSelected = true;
}
}
public static DependencyProperty SelectedNode_Property =
DependencyProperty.Register(
"SelectedCustomThing",
typeof(CustomThing),
typeof(CustomTreeView),
new FrameworkPropertyMetadata(
null,
FrameworkPropertyMetadataOptions.None,
SelectedNodeChanged));
public CustomTreeView(): base()
{
this.SelectedItemChanged += new RoutedPropertyChangedEventHandler<object>(SelectedItemChanged_CustomHandler);
}
void SelectedItemChanged_CustomHandler(object sender, RoutedPropertyChangedEventArgs<object> e)
{
SetValue(SelectedNode_Property, SelectedItem);
}
private static void SelectedNodeChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
{
var treeView = d as CustomTreeView;
var newNode = e.NewValue as CustomThing;
treeView.SelectedCustomThing = (CustomThing)e.NewValue;
}
}
用这个XAML:
<local:CustonTreeView ItemsSource="{Binding TreeRoot}"
SelectedCustomThing="{Binding SelectedNode,Mode=TwoWay}">
<TreeView.ItemContainerStyle>
<Style TargetType="TreeViewItem">
<Setter Property="IsSelected" Value="{Binding IsSelected, Mode=TwoWay}" />
</Style>
</TreeView.ItemContainerStyle>
</local:CustonTreeView>
还有一种方法可以在不使用Interaction.Behaviors的情况下创建XAML可绑定SelectedItem属性。
public static class BindableSelectedItemHelper
{
#region Properties
public static readonly DependencyProperty SelectedItemProperty = DependencyProperty.RegisterAttached("SelectedItem", typeof(object), typeof(BindableSelectedItemHelper),
new FrameworkPropertyMetadata(null, OnSelectedItemPropertyChanged));
public static readonly DependencyProperty AttachProperty = DependencyProperty.RegisterAttached("Attach", typeof(bool), typeof(BindableSelectedItemHelper), new PropertyMetadata(false, Attach));
private static readonly DependencyProperty IsUpdatingProperty = DependencyProperty.RegisterAttached("IsUpdating", typeof(bool), typeof(BindableSelectedItemHelper));
#endregion
#region Implementation
public static void SetAttach(DependencyObject dp, bool value)
{
dp.SetValue(AttachProperty, value);
}
public static bool GetAttach(DependencyObject dp)
{
return (bool)dp.GetValue(AttachProperty);
}
public static string GetSelectedItem(DependencyObject dp)
{
return (string)dp.GetValue(SelectedItemProperty);
}
public static void SetSelectedItem(DependencyObject dp, object value)
{
dp.SetValue(SelectedItemProperty, value);
}
private static bool GetIsUpdating(DependencyObject dp)
{
return (bool)dp.GetValue(IsUpdatingProperty);
}
private static void SetIsUpdating(DependencyObject dp, bool value)
{
dp.SetValue(IsUpdatingProperty, value);
}
private static void Attach(DependencyObject sender, DependencyPropertyChangedEventArgs e)
{
TreeListView treeListView = sender as TreeListView;
if (treeListView != null)
{
if ((bool)e.OldValue)
treeListView.SelectedItemChanged -= SelectedItemChanged;
if ((bool)e.NewValue)
treeListView.SelectedItemChanged += SelectedItemChanged;
}
}
private static void OnSelectedItemPropertyChanged(DependencyObject sender, DependencyPropertyChangedEventArgs e)
{
TreeListView treeListView = sender as TreeListView;
if (treeListView != null)
{
treeListView.SelectedItemChanged -= SelectedItemChanged;
if (!(bool)GetIsUpdating(treeListView))
{
foreach (TreeViewItem item in treeListView.Items)
{
if (item == e.NewValue)
{
item.IsSelected = true;
break;
}
else
item.IsSelected = false;
}
}
treeListView.SelectedItemChanged += SelectedItemChanged;
}
}
private static void SelectedItemChanged(object sender, RoutedEventArgs e)
{
TreeListView treeListView = sender as TreeListView;
if (treeListView != null)
{
SetIsUpdating(treeListView, true);
SetSelectedItem(treeListView, treeListView.SelectedItem);
SetIsUpdating(treeListView, false);
}
}
#endregion
}
然后你可以在你的XAML中使用它:
<TreeView helper:BindableSelectedItemHelper.Attach="True"
helper:BindableSelectedItemHelper.SelectedItem="{Binding SelectedItem, Mode=TwoWay}">
