Question

我有一个典型的MVVM场景：我有一个绑定到StepsViewModel列表的ListBox。我定义了一个DataTemplate，以便StepViewModel呈现为StepViews。 StepView UserControl有一组标签和TextBoxs。

我想要做的是选择在关注textBox时包装StepView的ListBoxItem。我尝试使用以下触发器为我的TextBox创建一个样式：

<Trigger Property="IsFocused" Value="true">
    <Setter TargetName="{Binding RelativeSource={RelativeSource Mode=FindAncestor, AncestorType={x:Type ListBoxItem}}}" Property="IsSelected" Value="True"/>
</Trigger>

但是我收到一个错误，告诉我TextBox没有IsSelected属性。我现在，但Target是一个ListBoxItem。我怎样才能使它发挥作用？

Answer 1

如果有任何子节点聚焦，则只有一个只读属性IsKeyboardFocusWithin将设置为true。您可以使用它在Trigger：

中设置ListBoxItem.IsSelected

<ListBox ItemsSource="{Binding SomeCollection}" HorizontalAlignment="Left">
    <ListBox.ItemContainerStyle>
        <Style TargetType="{x:Type ListBoxItem}">
            <Style.Triggers>
                <Trigger Property="IsKeyboardFocusWithin" Value="True">
                    <Setter Property="IsSelected" Value="True" />
                </Trigger>
            </Style.Triggers>
        </Style>
    </ListBox.ItemContainerStyle>
    <ListBox.ItemTemplate>
        <DataTemplate>
            <TextBox Width="100" Margin="5" Text="{Binding Name}"/>
        </DataTemplate>
    </ListBox.ItemTemplate>
</ListBox>

Answer 2

正如Jordan0Day正确指出的那样，使用IsKeyboardFocusWithin解决方案确实存在很大的问题。在我的情况下，工具栏中关于ListBox的按钮也不再起作用。焦点同样的问题。单击按钮时，ListBoxItem会松开Focus并且Button会更新其CanExecute方法，这会导致在执行按钮单击命令之前暂停按钮。

对我来说，更好的解决方案是使用ItemContainerStyle EventSetter，如本文所述：ListboxItem selection when the controls inside are used

XAML：

<Style x:Key="MyItemContainer.Style" TargetType="{x:Type ListBoxItem}">
    <Setter Property="Background" Value="LightGray"/>
    <EventSetter Event="GotKeyboardFocus" Handler="OnListBoxItemContainerFocused" />
    <Setter Property="Template">
        <Setter.Value>
            <ControlTemplate TargetType="{x:Type ListBoxItem}">
                <Border x:Name="backgroundBorder" Background="White">
                    <ContentPresenter Content="{TemplateBinding Content}"/>
                </Border>
            <ControlTemplate.Triggers>
                 <Trigger Property="IsSelected" Value="True">
                     <Setter TargetName="backgroundBorder" Property="Background" Value="#FFD7E6FC"/>
                 </Trigger>
             </ControlTemplate.Triggers>
         </ControlTemplate>
     </Setter.Value>
 </Setter>
</Style>

视图背后代码中的EventHandler：

private void OnListBoxItemContainerFocused(object sender, RoutedEventArgs e)
{
    (sender as ListBoxItem).IsSelected = true;
}

Answer 3

实现这一目标的一种方法是使用附加属性实现自定义行为。基本上，附加属性将使用样式应用于ListBoxItem，并将连接到他们的GotFocus事件。如果控件的任何后代获得焦点，甚至会触发，因此适合此任务。在事件处理程序中，IsSelected设置为true。

我为你写了一个小例子：

行为类：

public class MyBehavior
{
    public static bool GetSelectOnDescendantFocus(DependencyObject obj)
    {
        return (bool)obj.GetValue(SelectOnDescendantFocusProperty);
    }

    public static void SetSelectOnDescendantFocus(
        DependencyObject obj, bool value)
    {
        obj.SetValue(SelectOnDescendantFocusProperty, value);
    }

    public static readonly DependencyProperty SelectOnDescendantFocusProperty =
        DependencyProperty.RegisterAttached(
            "SelectOnDescendantFocus",
            typeof(bool),
            typeof(MyBehavior),
            new UIPropertyMetadata(false, OnSelectOnDescendantFocusChanged));

    static void OnSelectOnDescendantFocusChanged(
        DependencyObject d, DependencyPropertyChangedEventArgs e)
    {
        ListBoxItem lbi = d as ListBoxItem;
        if (lbi == null) return;
        bool ov = (bool)e.OldValue;
        bool nv = (bool)e.NewValue;
        if (ov == nv) return;
        if (nv)
        {
            lbi.GotFocus += lbi_GotFocus;
        }
        else
        {
            lbi.GotFocus -= lbi_GotFocus;
        }
    }

    static void lbi_GotFocus(object sender, RoutedEventArgs e)
    {
        ListBoxItem lbi = sender as ListBoxItem;
        lbi.IsSelected = true;
    }
}

Window XAML：

<Window x:Class="q2960098.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:sys="clr-namespace:System;assembly=mscorlib"
        Title="MainWindow" Height="350" Width="525" xmlns:my="clr-namespace:q2960098">
    <Window.Resources>
        <DataTemplate x:Key="UserControlItemTemplate">
            <Border BorderBrush="Black" BorderThickness="5" Margin="10">
                <my:UserControl1/>
            </Border>
        </DataTemplate>
        <XmlDataProvider x:Key="data">
            <x:XData>
                <test xmlns="">
                    <item a1="1" a2="2" a3="3" a4="4">a</item>
                    <item a1="a" a2="b" a3="c" a4="d">b</item>
                    <item a1="A" a2="B" a3="C" a4="D">c</item>
                </test>
            </x:XData>
        </XmlDataProvider>
        <Style x:Key="MyBehaviorStyle" TargetType="ListBoxItem">
            <Setter Property="my:MyBehavior.SelectOnDescendantFocus" Value="True"/>
        </Style>
    </Window.Resources>
    <Grid>
        <ListBox ItemTemplate="{StaticResource UserControlItemTemplate}"
                 ItemsSource="{Binding Source={StaticResource data}, XPath=//item}"
                 HorizontalContentAlignment="Stretch"
                 ItemContainerStyle="{StaticResource MyBehaviorStyle}">

        </ListBox>
    </Grid>
</Window>

用户控件XAML：

<UserControl x:Class="q2960098.UserControl1"
             xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
             xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
             xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006" 
             xmlns:d="http://schemas.microsoft.com/expression/blend/2008" 
             mc:Ignorable="d" 
             d:DesignHeight="300" d:DesignWidth="300">
    <UniformGrid>
        <TextBox Margin="10" Text="{Binding XPath=@a1}"/>
        <TextBox Margin="10" Text="{Binding XPath=@a2}"/>
        <TextBox Margin="10" Text="{Binding XPath=@a3}"/>
        <TextBox Margin="10" Text="{Binding XPath=@a4}"/>
    </UniformGrid>
</UserControl>

Answer 4

如果您创建一个用户控件，然后将其用作DataTemplate它似乎更干净。然后，您不必使用100％无法正常工作的脏样式触发器。

Answer 5

编辑：其他人在其他问题上已经有了相同的答案：https://stackoverflow.com/a/7555852/2484737

继续Maexs的回答，使用EventTrigger而不是EventSetter消除了代码隐藏的需要：

<Style.Triggers>
    <EventTrigger RoutedEvent="GotKeyboardFocus">
        <BeginStoryboard>
            <Storyboard >
                <BooleanAnimationUsingKeyFrames Storyboard.TargetProperty="IsSelected" >
                    <DiscreteBooleanKeyFrame Value="True" KeyTime="0:0:0"/>
                </BooleanAnimationUsingKeyFrames>
            </Storyboard>
        </BeginStoryboard>
    </EventTrigger>
</Style.Triggers>

当子TextBox为Focused时设置ListBoxItem.IsSelected

5 个答案: