ListView 扩展器在过滤器搜索时重置

问题描述

我已经设置了一个绑定到视图模型的简单 WPF ListView，ListView 使用 CollectionViewSource 根据各种属性对项目进行排序以动态创建 ListView 层次结构 - 这很好用。

我还添加了一个过滤器以允许例如搜索 ListView - 这也很有效。

我遇到的问题是，当用户在搜索框中键入一些文本时，搜索工作，但它关闭了所有扩展器。

每次在搜索框中输入一个字母时，所有扩展器都会再次关闭。

这对用户来说很烦人，有什么办法可以在搜索过程中和搜索后保持扩展器状态不变？

WPF 例程将狗分成不同的组。

狗类：

    public partial class Dogs : viewmodelBase
{

    //Group one nesting level
    private string _l1grouping;
    public string L1grouping
    {
        get
        {
            return _l1grouping;
        }
        set
        {
            _l1grouping = value;
            OnPropertyChanged(nameof(L1grouping));
        }
    }

    //Group two nesting level
    private string _l2grouping;
    public string L2grouping
    {
        get
        {
            return _l2grouping;
        }
        set
        {
            _l2grouping = value;
            OnPropertyChanged(nameof(L2grouping));
        }
    }

    //Group three nesting level
    private string _l3grouping;
    public string L3grouping
    {
        get
        {
            return _l3grouping;
        }
        set
        {
            _l3grouping = value;
            OnPropertyChanged(nameof(L3grouping));
        }
    }

    //Name
    private string _name;
    public string Name
    {
        get => _name;
        set
        {
            if (_name != value)
            {
                _name = value;
                OnPropertyChanged(nameof(Name));
            }
        }
    }
}

查看模型类：

    class MainWindowviewmodel : viewmodelBase
{
    public ICollectionView DogsCollectionView { get; }

    private ObservableCollection<Dogs> _dogs = new ObservableCollection<Dogs>();

    public ObservableCollection<Dogs> Dogs
    {
        get => _dogs;
        set
        {
            if (value != _dogs)
            {
                _dogs = value;
                OnPropertyChanged(nameof(Dogs));
            }
        }
    }

    private string _dogFilter = string.Empty;
    public string DogFilter
    {
        get
        {
            return _dogFilter;
        }
        set
        {
            _dogFilter = value;
            OnPropertyChanged(nameof(DogFilter));
            DogsCollectionView.Refresh();
        }
    }

    public MainWindowviewmodel()
    //Constructor
    {
        DogsCollectionView = CollectionViewSource.Getdefaultview(_dogs);

        //Set up filter
        DogsCollectionView.Filter = FilterbrowserItems;

        //Set up grouping
        DogsCollectionView.GroupDescriptions.Add(new PropertyGroupDescription(nameof(SaveExpanderState.Dogs.L1grouping)));
        DogsCollectionView.GroupDescriptions.Add(new PropertyGroupDescription(nameof(SaveExpanderState.Dogs.L2grouping)));
        DogsCollectionView.GroupDescriptions.Add(new PropertyGroupDescription(nameof(SaveExpanderState.Dogs.L3grouping)));
    }

    private bool FilterbrowserItems(object obj)
    {
        if (obj is Dogs check)
        {
            string nametocheck = check.Name.ToLower();
            return nametocheck.Contains(DogFilter.ToLower());
        }

        return false;
    }
}

创建模型的代码：

    public partial class MainWindow : Window
{
    MainWindowviewmodel Dogviewmodel
    {
        get;
        set;
    }

    public MainWindow()
    {
        InitializeComponent();

        Dogviewmodel = new MainWindowviewmodel();

        Dogviewmodel.Dogs.Add(new Dogs() { Name = "Max",L1grouping = "Large",L2grouping = "brown",L3grouping = "Fast" }); ;
        Dogviewmodel.Dogs.Add(new Dogs() { Name = "Bob",L1grouping = "Small",L3grouping = "Slow" });
        Dogviewmodel.Dogs.Add(new Dogs() { Name = "Fido",L3grouping = "Fast" });
        Dogviewmodel.Dogs.Add(new Dogs() { Name = "Brian",L3grouping = "Fast" });
        Dogviewmodel.Dogs.Add(new Dogs() { Name = "Steve",L2grouping = "Black",L3grouping = "Fast" });
        Dogviewmodel.Dogs.Add(new Dogs() { Name = "emma",L3grouping = "Slow" });
        Dogviewmodel.Dogs.Add(new Dogs() { Name = "Shep",L3grouping = "Fast" });
        Dogviewmodel.Dogs.Add(new Dogs() { Name = "Lassy",L2grouping = "White",L3grouping = "Fast" });
        Dogviewmodel.Dogs.Add(new Dogs() { Name = "Burt",L3grouping = "Fast" });
        Dogviewmodel.Dogs.Add(new Dogs() { Name = "Siggy",L3grouping = "Fast" });
        Dogviewmodel.Dogs.Add(new Dogs() { Name = "Heidi",L2grouping = "Black and White",L3grouping = "Fast" });
        Dogviewmodel.Dogs.Add(new Dogs() { Name = "Loki",L2grouping = "Yellow",L3grouping = "Fast" });

        ListViewDogs.DataContext = Dogviewmodel;

        FilterBoxText.DataContext = Dogviewmodel;
    }
}

和用于窗口的 XAML：

<Grid>
    <StackPanel Orientation="Vertical">
        <StackPanel Orientation="Vertical">
            <StackPanel Orientation="Horizontal"
                        Margin="10">
                <TextBlock Text="Filter: " />
                <TextBox x:Name="FilterBoxText"
                         Width="330"
                         Text="{Binding DogFilter,UpdateSourceTrigger=PropertyChanged}" />
            </StackPanel>

        </StackPanel>
        <ListView Name="ListViewDogs"
                  Margin="10,10,10"
                  Height="370"
                  ItemsSource="{Binding DogsCollectionView}"
                  IsTextSearchEnabled="False"
                  IsSynchronizedWithCurrentItem="True">

            <ListView.ItemTemplate>
                <DataTemplate>
                    <WrapPanel>
                        <TextBlock Text="{Binding Name}" />
                    </WrapPanel>
                </DataTemplate>
            </ListView.ItemTemplate>

            <ListView.GroupStyle>
                <GroupStyle>
                    <GroupStyle.ContainerStyle>
                        <Style targettype="{x:Type GroupItem}">
                            <Setter Property="Template">
                                <Setter.Value>
                                    <ControlTemplate>
                                        <Expander>
                                            <Expander.Header>
                                                <TextBlock Text="{Binding Name}"/>
                                            </Expander.Header>
                                            <ItemsPresenter />
                                        </Expander>
                                    </ControlTemplate>
                                </Setter.Value>
                            </Setter>
                        </Style>
                    </GroupStyle.ContainerStyle>
                </GroupStyle>
            </ListView.GroupStyle>
            
        </ListView>
    </StackPanel>
</Grid>

谢谢，我希望得到一些建议。

解决方法

暂无找到可以解决该程序问题的有效方法，小编努力寻找整理中！

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