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如何访问WPF GroupItem模板中的元素

expander controltemplate wpf c#

-1

polfosol à° _à° · 技术社区 · 6 年前

我有一个 ListView 里面装满了一些东西。这些项目有两个属性, ItemName 和 ItemGroup

<Grid>
    <Grid.Resources>
        <Style x:Key="groupStyle" TargetType="{x:Type GroupItem}">
            <Setter Property="Template">
                <Setter.Value>
                    <ControlTemplate>
                        <Expander IsExpanded="False" Header="{Binding Name}">
                            <ItemsPresenter />
                        </Expander>
                    </ControlTemplate>
                </Setter.Value>
            </Setter>
        </Style>
    </Grid.Resources>
    <ListView x:Name="lv">
        <ListView.View>
            <GridView>
                <GridViewColumn>
                    <GridViewColumn.CellTemplate>
                        <DataTemplate>
                            <TextBlock Text="{Binding ItemName}"/>
                        </DataTemplate>
                    </GridViewColumn.CellTemplate>
                </GridViewColumn>
            </GridView>
        </ListView.View>
        <ListView.GroupStyle>
            <GroupStyle ContainerStyle="{StaticResource groupStyle}"/>
        </ListView.GroupStyle>
    </ListView>
</Grid>

在后面的代码里

// here, list is the collection of items with mentioned properties.
lv.ItemsSource = list;
var view = (CollectionView) CollectionViewSource.GetDefaultView(lv.ItemsSource);
if (view.GroupDescriptions != null)
{
    view.GroupDescriptions.Clear();
    view.GroupDescriptions.Add(new PropertyGroupDescription("ItemGroup"));
}

现在一切顺利。但问题是,有时我想把 Expander IsExpanded 属性设置为true。我该怎么做?

编辑 :下面是我用来查找扩展器的方法,例如。 FindChildren<Expander>(lv) 但它总是返回一个空集合

public static IEnumerable<T> FindChildren<T>(DependencyObject obj) where T : DependencyObject
{
    if (obj == null)
    {
        yield break;
    }
    int vt_count = obj is Visual ? VisualTreeHelper.GetChildrenCount(obj) : 0;
    var children = vt_count > 0
        ? Enumerable.Range(0, vt_count).Select(n => VisualTreeHelper.GetChild(obj, n))
        : LogicalTreeHelper.GetChildren(obj).OfType<DependencyObject>();

    foreach (var child in children)
    {
        if (child is T)
        {
            yield return (T) child;
            continue;
        }
        foreach (T descendant in FindChildren<T>(child))
            yield return descendant;
    }
}

2 回复 | 直到 5 年前

mm8 6 年前

Expander 使用递归方法和 VisualTreeHelper 班级:

private void ExpandButton_Click(object sender, RoutedEventArgs e)
{
    foreach (Expander gi in FindVisualChildren<Expander>(lv))
    {
        gi.IsExpanded = true;
    }
}

private static IEnumerable<T> FindVisualChildren<T>(DependencyObject depObj) where T : DependencyObject
{
    if (depObj != null)
    {
        for (int i = 0; i < VisualTreeHelper.GetChildrenCount(depObj); i++)
        {
            DependencyObject child = VisualTreeHelper.GetChild(depObj, i);
            if (child != null && child is T)
            {
                yield return (T)child;
            }

            foreach (T childOfChild in FindVisualChildren<T>(child))
            {
                yield return childOfChild;
            }
        }
    }
}

编辑: 如果你想在设置好 ItemsSource ListView ,您需要等待容器创建完毕。处理 Loaded

public MainWindow()
{
    InitializeComponent();

    // here, list is the collection of items with mentioned properties.
    lv.ItemsSource = list;
    var view = (CollectionView)CollectionViewSource.GetDefaultView(lv.ItemsSource);
    if (view.GroupDescriptions != null)
    {
        view.GroupDescriptions.Clear();
        view.GroupDescriptions.Add(new PropertyGroupDescription("ItemGroup"));
    }

    Loaded += (s, e) =>
    {
        foreach (Expander gi in FindVisualChildren<Expander>(lv))
        {
            gi.IsExpanded = true;
        }
    };
}

polfosol à° _à° 6 年前

奇怪地 ,由@mm8发布的答案不起作用,我也不知道为什么。但不管怎样,我还是设法解决了这个问题。关键是绑定 IsExpanded 扩展程序的属性转换为 ListView ,例如其标签:

<ControlTemplate>
    <Expander Header="{Binding Name}">
        <Expander.IsExpanded>
            <Binding RelativeSource="{RelativeSource FindAncestor, AncestorType=ListView}" Path="Tag" />
        </Expander.IsExpanded>
        <ItemsPresenter />
    </Expander>
</ControlTemplate>

然后你就可以控制 I扩展 lv.Tag = true; 或 lv.Tag = false; 在密码里。