从 DataTrigger 在 WPF TreeViewItem 上设置 IsExpanded [英] Setting IsExpanded on a WPF TreeViewItem from a DataTrigger
问题描述
我正在尝试使用条件模板在 XAML 中设置我的 TreeView 项目的 IsExpanded 属性:
I'm trying to set the IsExpanded property of my TreeView items using a conditional template, in the XAML:
<DataTrigger Binding="{Binding MyStatus}" Value="Opened">
<Setter TargetName="MyTextBlock" Property="Foreground" Value="Green"/>
<Setter Property="TreeViewItem.IsExpanded" Value="True" />
</DataTrigger>
当我从 C# 代码中设置 MyStatus 属性时，颜色会发生变化(因此 DataTrigger 可以工作)，但节点没有展开.
When I set the MyStatus property from the C# code, the colors are changed (so the DataTrigger works), but the nodes aren't expanded.
_myItems[0].MyStatus = MyStatus.Opened;
如何从 DataTrigger 设置 TreeViewItem.IsExpanded 属性?
How can I set the TreeViewItem.IsExpanded property from a DataTrigger?
当我启动应用程序时，颜色设置正确，但绿色节点没有展开:
When I start the application, the colors are correctly set, but the green node isn't expanded:
并且改变_myItems[0].MyStatus和_myItems[1].MyStatus的值后，颜色也相应改变了，但绿色节点仍然不是't 展开.
And after changing the value of _myItems[0].MyStatus and _myItems[1].MyStatus, the colors are changed accordingly, but the green node still isn't expanded.
完整的代码有点长，但它是 90% 的样板.
The full code is a bit long, but it's 90% boilerplate.
<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));
}
}
}
}
推荐答案
这里有一些错误.第一个是您在 HierarchicalDataTemplate 上设置属性 TreeViewItem.IsSelected.这行不通.相反，您需要在 TreeView 上设置一个 ItemContainerStyle:
There are a few things wrong here. The first is that you are setting the property TreeViewItem.IsSelected on a HierarchicalDataTemplate. This won't work. Instead, you're going to need to set an ItemContainerStyle on the TreeView:
<TreeView>
<TreeView.ItemContainerStyle>
<Style TargetType="{x:Type TreeViewItem}">
<!-- put logic for handling expansion here -->
</Style>
</TreeView.ItemContainerStyle>
</TreeView>
但是，您不能将 Trigger 放在此处.由于DependencyProperty 值优先，如果您的用户单击节点要展开或折叠它们，您的触发器将不会在优先级列表中排名第一(即本地值).因此，最好的办法是创建一个新的 IValueConverter 以将 MyStatus 转换为 bool.然后在 Style 的 Setter 中设置一个 TwoWay 绑定:
You can't just put the Trigger in here, however. Because of DependencyProperty value precedence, if your user clicks on the nodes to expand or collapse them, your triggers won't be #1 on the precedence list (that is a local value). Therefore, your'e best bet is to create a new IValueConverter to convert from MyStatus to a bool. And then setup a TwoWay binding in a Setter in the Style:
<Style TargetType="{x:Type TreeViewItem}">
<Setter Property="IsExpanded"
Value="{Binding MyStatus, Converter={StaticResource statusToBool}}" />
</Style>
还有你的转换器:
public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
{
return ((MyStatus)value) == MyStatus.Opened;
}
public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
{
return ((bool)value) ? MyStatus.Opened : MyStatus.Closed;
}
这篇关于从 DataTrigger 在 WPF TreeViewItem 上设置 IsExpanded的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！
