c# - 延迟取消选择 ListBoxItem

Question

我想实现一种效果，其中 ListBoxItem 被选中(突出显示)几秒钟，然后被取消选中。尝试使用淡入淡出效果实现简单的控件突出显示，但为了使事情正常进行，我需要相应地更改一个属性。

我有一个 IsSelected 属性绑定(bind)到我的 View 模型属性:

<Style TargetType="{x:Type ListBoxItem}">
    <Setter Property="IsSelected" Value="{Binding IsSelected, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}" />
</Style>

我的属性(property)看起来是这样的:

public bool IsSelected
{
    get => _isSelected;
    set
    {
        // Update value
        _isSelected = value;

        // Raise property changed
        OnPropertyChanged(nameof(IsSelected));
    }
}

我试过使用延迟绑定(bind):

<ControlTemplate TargetType="{x:Type ListBoxItem}">
    <ControlTemplate.Triggers>
        <!--  Deselect after 5 seconds  -->
        <DataTrigger Binding="{Binding IsSelected, Delay=5000}" Value="True">
            <Setter Property="IsSelected" Value="False" />
        </DataTrigger>
    </ControlTemplate.Triggers>
</ControlTemplate>

我也尝试过使用 Storyboard:

<ControlTemplate TargetType="{x:Type ListBoxItem}">
    <ControlTemplate.Triggers>
        <!--  Deselect after 5 seconds  -->
        <DataTrigger Binding="{Binding IsSelected}" Value="True">
            <DataTrigger.EnterActions>
                <BeginStoryboard>
                    <Storyboard>
                        <BooleanAnimationUsingKeyFrames Storyboard.TargetProperty="IsSelected">
                            <DiscreteBooleanKeyFrame KeyTime="00:00:05" Value="False" />
                        </BooleanAnimationUsingKeyFrames>
                    </Storyboard>
                </BeginStoryboard>
            </DataTrigger.EnterActions>
        </DataTrigger>
    </ControlTemplate.Triggers>
</ControlTemplate>

不幸的是，上述方法似乎都没有更新我的 IsSelected 属性并且 ListBoxItem 保持选中状态并突出显示。

我希望在 XAML(或扩展)、MVVM 风格、无代码隐藏和无浪费的计时器中完成此操作 - 这可能吗？ 如果是这样，我如何正确取消选择延迟的 ListBoxItem？

Answer 1

这是一个附加行为的例子，它或多或少应该做你想做的事:

public class DeselectBehavior
{
    public static bool GetIsEnabled(ListBox listBox)
    {
        return (bool)listBox.GetValue(IsEnabledProperty);
    }

    public static void SetIsEnabled(ListBox listBox, bool value)
    {
        listBox.SetValue(IsEnabledProperty, value);
    }

    public static readonly DependencyProperty IsEnabledProperty =
        DependencyProperty.RegisterAttached(
        "IsEnabled",
        typeof(bool),
        typeof(DeselectBehavior),
        new UIPropertyMetadata(false, OnChanged));

    private static void OnChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
    {
        ListBox listBox = d as ListBox;
        if((bool)e.NewValue)
        {
            listBox.AddHandler(ListBoxItem.SelectedEvent, (RoutedEventHandler)OnListBoxItemSelected, true);
        }
        else
        {
            listBox.RemoveHandler(ListBoxItem.SelectedEvent, (RoutedEventHandler)OnListBoxItemSelected);
        }
    }

    private static async void OnListBoxItemSelected(object sender, RoutedEventArgs e)
    {
        await Task.Delay(2000);
        ListBoxItem listBoxItem = e.OriginalSource as ListBoxItem;
        if (listBoxItem != null)
            listBoxItem.IsSelected = false;
    }
}

XAML:

    <ListBox ... local:DeselectBehavior.IsEnabled="True">
    ...