[英]Setting IsExpanded on a WPF TreeViewItem from a DataTrigger
我正在尝试使用条件模板在XAML
设置我的TreeView
项目的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,颜色会发生变化(因此 DataTrigger 可以工作),但不会展开节点。
_myItems[0].MyStatus = MyStatus.Opened;
如何从DataTrigger
设置TreeViewItem.IsExpanded
属性?
当我启动应用程序时,颜色设置正确,但绿色节点没有展开:
并且更改_myItems[0].MyStatus
和_myItems[1].MyStatus
,颜色也相应更改,但绿色节点仍未展开。
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>
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));
}
}
}
}
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
值优先 ,如果用户单击节点以展开或折叠它们,则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Style
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, Type targetType, object parameter, CultureInfo culture)
{
return ((bool)value) ? MyStatus.Opened : MyStatus.Closed;
}
我不得不做类似的事情,我这样解决了:
<TreeView ItemsSource="{Binding source}"
SnapsToDevicePixels="{Binding Path=myStatusToBool}"
>
<TreeView.ItemContainerStyle>
<Style>
<Setter Property="TreeViewItem.IsExpanded"
Value="False"
/>
<Style.Triggers>
<DataTrigger Binding="{Binding Path=SnapsToDevicePixels,RelativeSource={RelativeSource AncestorType=TreeView}}"
Value="True">
<Setter Property="TreeViewItem.IsExpanded"
Value="True"
/>
</DataTrigger>
</Style.Triggers>
</Style>
</TreeView.ItemContainerStyle>
<TreeView.Resources>
.....
.....
</TreeView.Resources>
</TreeView>
我遇到了同样的问题,但在没有值转换器的情况下解决了它:
<TreeView.ItemContainerStyle>
<Style TargetType="{x:Type TreeViewItem}" BasedOn="{StaticResource {x:Type TreeViewItem}}">
<Style.Triggers>
<DataTrigger Binding="{Binding IsVisible}" Value="False">
<Setter Property="Visibility" Value="Collapsed" />
</DataTrigger>
<DataTrigger Binding="{Binding IsExpanded}" Value="True">
<Setter Property="IsExpanded" Value="True" />
</DataTrigger>
</Style.Triggers>
</Style>
</TreeView.ItemContainerStyle>
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