Question

扩展了ListBox以给我一个水平的List Box，即在XAML中：

<ListBox x:Class="Renishaw.Inspire.InTheatreCompanion.View.HorizontalListBox"
         xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
         xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
         Style="{x:Null}">

    <ListBox.ItemsPanel>
        <ItemsPanelTemplate>
            <VirtualizingStackPanel Name="ItemContainer" 
                                    Orientation="Horizontal"/>
        </ItemsPanelTemplate>
    </ListBox.ItemsPanel>


</ListBox>

并在

背后的代码中

public partial class HorizontalListBox : ListBox
   {
      public static readonly DependencyProperty IndentItemsProperty = DependencyProperty.Register(
         "IndentItems", typeof(double), typeof(HorizontalListBox), new PropertyMetadata(0.0, new PropertyChangedCallback(OnIndentItemsChanged)));

      public HorizontalListBox()
      {
         InitializeComponent();
      }

      public double IndentItems
      {
         get { return (double)GetValue(IndentItemsProperty); }
         set { SetValue(IndentItemsProperty, value); }
      }

      private static void OnIndentItemsChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
      {
         var horizontalListBox = (HorizontalListBox)d;
         var thickness = new Thickness((double)e.NewValue, 0, 0, 0);
         horizontalListBox.ItemContainer.Margin = thickness;
      }

      public static void SetIndentItems(DependencyObject obj, double thickness)
      {
         obj.SetValue(IndentItemsProperty, thickness);
      }

      public static double GetIndentItems(DependencyObject obj)
      {
         return (double)obj.GetValue(IndentItemsProperty);
      }

   }

其中依赖项属性IndentItems允许我通过设置用于包含项目的VirtualizingStackPanel的边距来将项目缩进设定的金额。但是，尝试构建它会抛出一个错误，告诉我＆＃34; HorizonatlListBox不包含＆＃39; ItemContainer＆＃39;＆＃34;即使已经在xaml中给出了该名称。我可能会出错的任何想法？

Answer 1

在模板中设置元素的名称不会在声明模板的类中生成成员，即您的HorizontalListBox类中没有ItemContainer成员。

除此之外，您的IndentItems属性似乎是多余的，因为ListBox已经有Padding属性：

<local:HorizontalListBox Padding="50,0,0,0" .../>

现在可能不再需要派生的HorizontalListBox，因为你可以这样写：

<ListBox Padding="50,0,0,0" ...>
    <ListBox.ItemsPanel>
        <ItemsPanelTemplate>
            <VirtualizingStackPanel Orientation="Horizontal"/>
        </ItemsPanelTemplate>
    </ListBox.ItemsPanel>
<ListBox/>

Answer 2

您可以比创建新控件更简单地满足您的要求：

<App.Resources>
    <ItemsPanelTemplate x:Key="HorizontalStackPanelTemplate">
        <VirtualizingStackPanel Orientation="Horizontal" />
    <ItemsPanelTemplate>
</App.Resources>

<ListBox ItemsSource="{Binding source}" Padding ="50,0,0,0"
         ItemsPanel="{StaticResource HorizontalStackPanelTemplate}" />

Answer 3

如何使用转换器？

<Window x:Class="ListBoxMargins.MainWindow"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:local="clr-namespace:ListBoxMargins"
    Title="MainWindow" Height="350" Width="525">
<Grid>
    <Grid.Resources>
        <local:StackConverter x:Key="StackConverter"/>
    </Grid.Resources>
    <ListBox ItemsSource="{Binding source}">
        <ListBox.ItemsPanel>
            <ItemsPanelTemplate>
                <VirtualizingStackPanel Name="ItemContainer" 
                                Orientation="Horizontal" 
                                Margin="{Binding RelativeSource={RelativeSource Self}, Path=IsKeyboardFocusWithin, Converter={StaticResource StackConverter}}"/>
            </ItemsPanelTemplate>
        </ListBox.ItemsPanel>
    </ListBox>
</Grid>

public partial class MainWindow : Window
{
    public ObservableCollection<string> source { get; set; }
    public MainWindow()
    {
        InitializeComponent();
        source = new ObservableCollection<string>();
        source.Add("Test element1");
        source.Add("Test element2");
        source.Add("Test element3");
        this.DataContext = this;
    }
}

我没有在这里进行所有检查，但在我的测试中，面板是缩进的。

public class StackConverter : IValueConverter
{
    public object Convert(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
    {
        bool focused = (bool)value;

        if (focused)
        {
            return new Thickness(50);
        }
        else
        {
            return new Thickness(0);
        }
    }

    public object ConvertBack(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
    {
        throw new NotImplementedException();
    }
}

WPF扩展列表框没有找到定义

3 个答案: