MVVM处理TreeView的SelectedItem的绑定的两种方式
TreeView的SelectedItem不支持MVVM绑定：
因为它是只读的。
有时候我们就需要对它进行绑定
1.使用自定义Behavior
需要引用System.Windows.Interactivity.dll
自定义Behavior如下：
public class TreeViewBehavior : Behavior<TreeView>
{
public object SelectedItem
{
get {
return (object)GetValue(SelectedItemProperty); }
set {
SetValue(SelectedItemProperty, value); }
}
// Using a DependencyProperty as the backing store for SelectedItem. This enables animation, styling, binding, etc...
public static readonly DependencyProperty SelectedItemProperty =
DependencyProperty.Register("SelectedItem", typeof(object), typeof(TreeViewBehavior), new PropertyMetadata(null, OnSelectedItemChanged));
private static void OnSelectedItemChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
{
var treeViewHelper = d as TreeViewBehavior;
SetItemSelected(treeViewHelper.AssociatedObject, e.NewValue);
}
private static void SetItemSelected(TreeView tree, object context)
{
for (int i = 0; i < tree.Items.Count; i++)
{
var treeItem = tree.ItemContainerGenerator.ContainerFromIndex(i) as TreeViewItem;
if (SetItemSelected(treeItem,context))
{
return;
}
}
}
private static bool SetItemSelected(TreeViewItem treeViewItem,object datacontext)
{
if (treeViewItem.DataContext == datacontext)
{
treeViewItem.IsSelected = true;
return true;
}
for (int i = 0; i < treeViewItem.Items.Count; i++)
{
var subTreeViewItem = treeViewItem.ItemContainerGenerator.ContainerFromIndex(i) as TreeViewItem;
if (subTreeViewItem != null && subTreeViewItem.DataContext == datacontext)
{
subTreeViewItem.IsSelected = true;
return true;
}
}
return false;
}
protected override void OnAttached()
{
base.OnAttached();
this.AssociatedObject.SelectedItemChanged += AssociatedObject_Selected;
}
private void AssociatedObject_Selected(object sender, System.Windows.RoutedEventArgs e)
{
var treeView = sender as TreeView;
this.SelectedItem = treeView?.SelectedItem;
}
protected override void OnDetaching()
{
base.OnDetaching();
this.AssociatedObject.SelectedItemChanged -= AssociatedObject_Selected;
}
}
前台使用：
<Grid>
<Grid.ColumnDefinitions>
<ColumnDefinition></ColumnDefinition>
<ColumnDefinition></ColumnDefinition>
</Grid.ColumnDefinitions>
<TreeView ItemsSource="{Binding Nodes}">
<TreeView.ItemTemplate>
<HierarchicalDataTemplate ItemsSource="{Binding Children}">
<Grid>
<TextBlock Text="{Binding Name}"></TextBlock>
</Grid>
</HierarchicalDataTemplate>
</TreeView.ItemTemplate>
<i:Interaction.Behaviors>
<local:TreeViewBehavior SelectedItem="{Binding SelectedItem,Mode=TwoWay}"></local:TreeViewBehavior>
</i:Interaction.Behaviors>
</TreeView>
<Label Grid.Column="1" Content="{Binding SelectedItem.Name}"></Label>
<Button Grid.Column="1" Margin="100" Click="Button_Click"></Button>
</Grid>
2.使用附加属性和注册类的路由事件
附加属性及类的路由事件处理逻辑如下：
class TreeViewHelper
{
static TreeViewHelper()
{
EventManager.RegisterClassHandler(typeof(TreeView), TreeView.SelectedItemChangedEvent, new RoutedEventHandler(OnSeletedItemChanged));
}
public static object GetSelectedItem(DependencyObject obj)
{
return (object)obj.GetValue(SelectedItemProperty);
}
public static void SetSelectedItem(DependencyObject obj, object value)
{
obj.SetValue(SelectedItemProperty, value);
}
// Using a DependencyProperty as the backing store for SelectedItem. This enables animation, styling, binding, etc...
public static readonly DependencyProperty SelectedItemProperty =
DependencyProperty.RegisterAttached("SelectedItem", typeof(object), typeof(TreeViewHelper), new PropertyMetadata(null,OnSelectedItemChanged));
private static void OnSelectedItemChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
{
SetItemSelected(d as TreeView, e.NewValue);
}
private static void SetItemSelected(TreeView tree, object context)
{
for (int i = 0; i < tree.Items.Count; i++)
{
var treeItem = tree.ItemContainerGenerator.ContainerFromIndex(i) as TreeViewItem;
if (SetItemSelected(treeItem, context))
{
return;
}
}
}
private static bool SetItemSelected(TreeViewItem treeViewItem, object datacontext)
{
if (treeViewItem.DataContext == datacontext)
{
treeViewItem.IsSelected = true;
return true;
}
for (int i = 0; i < treeViewItem.Items.Count; i++)
{
var subTreeViewItem = treeViewItem.ItemContainerGenerator.ContainerFromIndex(i) as TreeViewItem;
if (subTreeViewItem != null && subTreeViewItem.DataContext == datacontext)
{
subTreeViewItem.IsSelected = true;
return true;
}
}
return false;
}
private static void OnSeletedItemChanged(object sender, RoutedEventArgs e)
{
var treeView = sender as TreeView;
SetSelectedItem(treeView,treeView.SelectedItem);
}
}
前台代码：
<Window x:Class="WPF_TreeViewTest.MainWindow"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
xmlns:local="clr-namespace:WPF_TreeViewTest"
mc:Ignorable="d"
Title="MainWindow" Height="450" Width="800">
<Grid>
<Grid.ColumnDefinitions>
<ColumnDefinition></ColumnDefinition>
<ColumnDefinition></ColumnDefinition>
</Grid.ColumnDefinitions>
<TreeView ItemsSource="{Binding Nodes}" local:TreeViewHelper.SelectedItem="{Binding SelectedItem,Mode=TwoWay,UpdateSourceTrigger=PropertyChanged}">
<TreeView.ItemTemplate>
<HierarchicalDataTemplate ItemsSource="{Binding Children}">
<Grid>
<TextBlock Text="{Binding Name}"></TextBlock>
</Grid>
</HierarchicalDataTemplate>
</TreeView.ItemTemplate>
</TreeView>
<Label Grid.Column="1" Content="{Binding SelectedItem.Name}"></Label>
<Button Grid.Column="1" Margin="100" Click="Button_Click"></Button>
</Grid>
</Window>