c# - 无法在 DropDownButton 中组织数据

Question

总结

我有一个 DropDownButton包含特定国家的所有联赛。所以本质上用户选择了 Nation来自ComboBox和 Leagues所选 Nation将添加到DropDownButton里面.直到这里没问题。

我需要做的是:整理Leagues在DropDownButton里面对于 Nation .所以想象一下 DropDownButton 里面我有这个组织:

Italy 
     Item1
     Item2
     Item3
England
     Item1
     Item2
Spain 
     Item1
     Item2
... etc ...

项目类型

如何查看项目是按国家/地区组织的。在解释我为实现此结果所做的工作之前，我不得不说我使用的是 CheckedListItem类，它本质上是一个绑定(bind) CheckBox 的类到 DropDownButton 的项目.这个类非常简单:

public class CheckedListItem<T> : INotifyPropertyChanged
{
    public event PropertyChangedEventHandler PropertyChanged;

    private bool isChecked;
    private T item;

    public CheckedListItem() { }

    public CheckedListItem(T item, bool isChecked = false)
    {
        this.item = item;
        this.isChecked = isChecked;
    }

    public T Item
    {
        get { return item; }
        set
        {
            item = value;
            PropertyChanged?.Invoke(this, new PropertyChangedEventArgs("Item"));
        }
    }

    public bool IsChecked
    {
        get { return isChecked; }
        set
        {
            isChecked = value;
            PropertyChanged?.Invoke(this, new PropertyChangedEventArgs("IsChecked"));
        }
    }
}

基本上使 Item<T> 可用如果被选中。为了使它在 XAML 中工作我在 Window.Resources 中写了这段代码:

<DataTemplate x:Key="NormalItemTemplate">
    <CheckBox IsChecked="{Binding IsChecked}" Content="{Binding Item.Name}" 
              x:Name="Leagues" Checked="Leagues_Checked" Unchecked="Leagues_Unchecked" />
</DataTemplate>

<DataTemplate x:Key="SelectionBoxTemplate" >
    <TextBlock Text="{DynamicResource displayedNation}"/>
</DataTemplate>

<DataTemplate x:Key="CombinedTemplate">
    <ContentPresenter x:Name="Presenter" Content="{Binding}" ContentTemplate="{StaticResource NormalItemTemplate}" />
    <DataTemplate.Triggers>
        <DataTrigger Binding="{Binding RelativeSource={RelativeSource FindAncestor, Controls:DropDownButton, 1}}"
                     Value="{x:Null}">
            <Setter TargetName="Presenter" Property="ContentTemplate"
                    Value="{StaticResource SelectionBoxTemplate}" />
        </DataTrigger>
    </DataTemplate.Triggers>
</DataTemplate>

<!--This is for the group item !-->

<Style TargetType="{x:Type GroupItem}" x:Key="containerStyle">
    <Setter Property="Template">
        <Setter.Value>
            <ControlTemplate TargetType="{x:Type GroupItem}">
                <!--Here, we tell that each group of item will be placed under Expander control,
                    and this expander control will by default will have style we defined in above code.-->
                <Expander IsExpanded="False" x:Name="ComboExpander" Header="{TemplateBinding Content}"
                          HeaderTemplate="{TemplateBinding ContentTemplate}">
                    <ItemsPresenter />
                </Expander>
            </ControlTemplate>
        </Setter.Value>
    </Setter>
</Style>

解释问题

现在实现DropDownButton中的分组我首先创建了一个 CollectionViewSource在Window.Resource像这样:

<CollectionViewSource Source="{Binding Leagues}" x:Key="GroupedData">
    <CollectionViewSource.GroupDescriptions>
        <PropertyGroupDescription PropertyName="Item.Country" />
    </CollectionViewSource.GroupDescriptions>
</CollectionViewSource>

<DataTemplate x:Key="GroupHeader">
    <TextBlock Text="{Binding Name}" Margin="10,0,0,0" Foreground="#989791"/>
</DataTemplate>

在DropDownButton我设置了这个结构:

<Controls:DropDownButton Content="Leagues" x:Name="LeagueMenu"
                          ItemsSource="{Binding Source={StaticResource GroupedData}}"
                          ItemTemplate="{StaticResource CombinedTemplate}" >
    <Controls:DropDownButton.GroupStyle>
        <GroupStyle ContainerStyle="{StaticResource containerStyle}"
                    HeaderTemplate="{StaticResource GroupHeader}">
        </GroupStyle>
    </Controls:DropDownButton.GroupStyle>
</Controls:DropDownButton>

(请注意，我正在使用 MahApp)

基本上我为 CheckedListItem 添加了一个模板和 ItemSource GroupedData你如何从上面的代码中看到绑定(bind) ObservableCollection的 Leagues .

数据填充

当 Nation被选中的列表Leagues可供选择 Nations将添加到 DropDownButton ，实现这个的代码:

private ObservableCollection<CheckedListItem<League>> _leagues = new ObservableCollection<CheckedListItem<League>>();
public ObservableCollection<CheckedListItem<League>> Leagues
{
    get
    {
        return _leagues;
    }
    set
    {
        _leagues = value;
        OnPropertyChanged();
    }
}

为添加 League 调用的方法所选 Nation这是:

public void GetLeagues(string link, string nation)
{
    Task.Run(() =>
    {
        var leagues = //get some collection

        foreach (var league in leagues)
        {
            var championship = new CheckedListItem<League>();
            championship.Item = new League { Name = league.Name, Link = league.Link, Country = nation };
            _leagues.Add(championship);
        }
    });
}

基本上我创建了一个 CheckedListItem的 League作为模型包含此属性:

public class League
{
    public string Name { get; set; }
    public string Link { get; set; }
    public string Country { get; set; }
}

应该出现的结果是这样的:

采取 from this tutorial .

但我却得到了这个结果:

如您所见，我没有使用 Nation 分组的 header 姓名。我在 XAML 或代码中也没有发现任何错误，所以我不知道为什么标题没有出现。

我知道这个问题可能有点复杂，所以如果有任何问题或更多细节，请问我，我会尽力回答。

演示解决方案:

https://mega.nz/#!g4YlTL4A!G4WXy1t64Q4yImYNvzgwGbieX1mhKnXO2OiuAO3FDg0

Answer 1

我不会尝试让第三方控件工作，而是更改工作 ComboBox 以满足您的需要:

MainWindow.xaml

<Controls:MetroWindow x:Class="WpfApplication1.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
        xmlns:Controls="http://metro.mahapps.com/winfx/xaml/controls"
        xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
        xmlns:local="clr-namespace:WpfApplication1"
        mc:Ignorable="d"
        Title="MainWindow" Height="700" Width="525">
    <Window.Resources>
        <ResourceDictionary>

            <CollectionViewSource Source="{Binding Leagues}" x:Key="GroupedData">
                <CollectionViewSource.GroupDescriptions>
                    <PropertyGroupDescription PropertyName="Item.Country" />
                </CollectionViewSource.GroupDescriptions>
            </CollectionViewSource>

            <DataTemplate x:Key="GroupHeader">
                <TextBlock Text="{Binding Name}" Margin="10,0,0,0" Foreground="#989791"/>
            </DataTemplate>

            <Style TargetType="{x:Type GroupItem}" x:Key="containerStyle">
                <Setter Property="Template">
                    <Setter.Value>
                        <ControlTemplate TargetType="{x:Type GroupItem}">
                            <Expander   IsExpanded="False" x:Name="ComboExpander" Header="{TemplateBinding Content}"
                                        HeaderTemplate="{StaticResource GroupHeader}">
                                <ItemsPresenter />
                            </Expander>
                        </ControlTemplate>
                    </Setter.Value>
                </Setter>
            </Style>

            <DataTemplate x:Key="NormalItemTemplate">
                <CheckBox IsChecked="{Binding IsChecked}" Content="{Binding Item.Name}" x:Name="Leagues" />
            </DataTemplate>
            <DataTemplate x:Key="HeaderTemplate">
                <TextBlock Text="Campionati"/>
            </DataTemplate>
            <DataTemplate x:Key="CombinedTemplate">
                <ContentPresenter x:Name="Presenter" 
                   Content="{Binding}"
                   ContentTemplate="{StaticResource NormalItemTemplate}" />
                <DataTemplate.Triggers>
                    <DataTrigger
                        Binding="{Binding RelativeSource={RelativeSource FindAncestor, ComboBoxItem, 1}}"
                        Value="{x:Null}">
                        <Setter TargetName="Presenter" Property="ContentTemplate"
                            Value="{StaticResource HeaderTemplate}" />
                    </DataTrigger>
                </DataTemplate.Triggers>
            </DataTemplate>
        </ResourceDictionary>

    </Window.Resources>    
    <Grid>
        <Grid.RowDefinitions>
            <RowDefinition/>
            <RowDefinition/>
            <RowDefinition/>
            <RowDefinition/>
        </Grid.RowDefinitions>
        <ComboBox x:Name="LeagueMenuComboBox" 
                  ItemsSource="{Binding Source={StaticResource GroupedData}}"
                  ItemTemplate="{StaticResource CombinedTemplate}"
                  HorizontalContentAlignment="Center">
            <ComboBox.GroupStyle>
                <GroupStyle ContainerStyle="{StaticResource containerStyle}"
                            HeaderTemplate="{StaticResource GroupHeader}">
                </GroupStyle>
            </ComboBox.GroupStyle>
        </ComboBox>
    </Grid>
</Controls:MetroWindow>