我正在尝试使用条件模板在XAML中设置我的TreeView项的IsExpanded属性：
<DataTrigger Binding="{Binding MyStatus}" Value="Opened">
<Setter TargetName="MyTextBlock" Property="Foreground" Value="Green"/>
<Setter Property="TreeViewItem.IsExpanded" Value="True" />
</DataTrigger>
当我从C#代码设置MyStatus属性时,颜色会更改(因此DataTrigger工作),但节点不会展开.
_myItems[0].MyStatus = MyStatus.Opened;
如何从DataTrigger设置TreeViewItem.IsExpanded属性？
当我启动应用程序时,颜色已正确设置,但绿色节点未展开：
在更改_myItems [0] .MyStatus和_myItems [1] .MyStatus的值后,颜色会相应更改,但绿色节点仍未展开.
完整代码(XAML)
完整的代码有点长,但它是90％的样板.
<Window x:Class="WpfApplication6.MainWindow"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
Title="MainWindow" Height="150" Width="250">
<DockPanel>
<DockPanel.Resources>
<HierarchicalDataTemplate ItemsSource="{Binding SubItems}" x:Key="MyTemplate">
<StackPanel Orientation="Horizontal">
<!-- ... -->
<TextBlock x:Name="MyTextBlock" Foreground="Green" Text="{Binding Name}" />
</StackPanel>
<HierarchicalDataTemplate.Triggers>
<DataTrigger Binding="{Binding MyStatus}" Value="Closed">
<Setter TargetName="MyTextBlock" Property="Foreground" Value="Red"/>
<Setter Property="TreeViewItem.IsExpanded" Value="False" />
</DataTrigger>
<DataTrigger Binding="{Binding MyStatus}" Value="Opened">
<Setter TargetName="MyTextBlock" Property="Foreground" Value="Green"/>
<Setter Property="TreeViewItem.IsExpanded" Value="True" />
</DataTrigger>
</HierarchicalDataTemplate.Triggers>
</HierarchicalDataTemplate>
</DockPanel.Resources>
<Button Name="button1" Click="button1_Click" DockPanel.Dock="Top" Content="Button1"/>
<TreeView Name="treeView1" ItemsSource="{Binding MyItems}" ItemTemplate="{StaticResource MyTemplate}"/>
</DockPanel>
</Window>
完整代码(C#)
using System;
using System.Collections.ObjectModel;
using System.ComponentModel;
using System.Windows;
namespace WpfApplication6
{
public partial class MainWindow : Window
{
private ObservableCollection<MyItemCollection> _myItems;
public MainWindow() {
InitializeComponent();
_myItems = new ObservableCollection<MyItemCollection> {
new MyItemCollection { Name = "Parent1",MyStatus = MyStatus.Closed,SubItems = { new MyItemCollection { Name = "Child1" } } },new MyItemCollection { Name = "Parent2",MyStatus = MyStatus.Opened,SubItems = { new MyItemCollection { Name = "Child2" } } }
};
DataContext = new {
MyItems = _myItems
};
}
private void button1_Click(object sender,RoutedEventArgs e) {
_myItems[0].MyStatus = MyStatus.Opened;
_myItems[1].MyStatus = MyStatus.Closed;
}
}
public enum MyStatus
{
Closed,Opened
}
public class MyItemCollection : INotifyPropertyChanged
{
public MyItemCollection() {
SubItems = new ObservableCollection<MyItemCollection>();
_myStatus = MyStatus.Closed;
}
public string Name { get; set; }
public ObservableCollection<MyItemCollection> SubItems { get; set; }
private MyStatus _myStatus;
public MyStatus MyStatus {
get { return _myStatus; }
set { _myStatus = value; NotifyPropertyChanged("MyStatus"); }
}
public event PropertyChangedEventHandler PropertyChanged;
private void NotifyPropertyChanged(String propertyName) {
PropertyChangedEventHandler handler = PropertyChanged;
if (handler != null) {
handler(this,new PropertyChangedEventArgs(propertyName));
}
}
}
}
解决方法
这里有一些问题.第一个是您在HierarchicalDataTemplate上设置属性TreeViewItem.IsSelected.这不行.相反,您需要在TreeView上设置ItemContainerStyle：
<TreeView>
<TreeView.ItemContainerStyle>
<Style TargetType="{x:Type TreeViewItem}">
<!-- put logic for handling expansion here -->
</Style>
</TreeView.ItemContainerStyle>
</TreeView>
但是,你不能把Trigger放在这里.由于DependencyProperty value precedence,如果您的用户单击节点以展开或折叠它们,您的触发器将不会是优先级列表上的#1(即本地值).因此,您最好的选择是创建一个新的IValueConverter,以便从MyStatus转换为bool.然后在样式的Setter中设置TwoWay绑定：
<Style TargetType="{x:Type TreeViewItem}">
<Setter Property="IsExpanded"
Value="{Binding MyStatus,Converter={StaticResource statusToBool}}" />
</Style>
而你的转换器：
public object Convert(object value,Type targetType,object parameter,CultureInfo culture)
{
return ((MyStatus)value) == MyStatus.Opened;
}
public object ConvertBack(object value,CultureInfo culture)
{
return ((bool)value) ? MyStatus.Opened : MyStatus.Closed;
}
