綁定自定義依賴屬性ListView寬度不更新

Question

我有一個IValueConverter名爲CategoryToGridViewConverter它有一個名爲ListViewWidthProperty DependencyProperty。我還從DependencyObject繼承了我的轉換器，以便它可以與DependencyProperties一起使用。這裏是我的轉換器是如何定義的：

internal class CategoryToGridViewConverter : DependencyObject, IValueConverter 
    { 
     public static readonly DependencyProperty ListViewWidthProperty = DependencyProperty.Register("ListViewWidth", typeof (double), 
                             typeof (CategoryToGridViewConverter), new PropertyMetadata(0d, PropertyChangedCallback)); 

     private static void PropertyChangedCallback(DependencyObject dependencyObject, DependencyPropertyChangedEventArgs dependencyPropertyChangedEventArgs) 
     { 
      Debug.WriteLine("ListViewWidth: " + dependencyPropertyChangedEventArgs.NewValue); 
     } 

     public double ListViewWidth { 
      get { return (double)GetValue(ListViewWidthProperty); } 
      set { SetValue(ListViewWidthProperty, value); } 
     } 

     public object Convert(object value, Type targetType, object parameter, CultureInfo culture) 
     { 
      //Not relevant 
     } 

     public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture) 
     { 
      //Not relevant 
     } 
    } 
} 

很簡單。然後，我創建XAML中該轉換器（在ListView的參考資料）是這樣的：

<ListView Grid.Row="0" BorderThickness="0" 
      ItemsSource="{Binding SelectedCategory.Entries}" 
      x:Name="listView" 
      SizeChanged="ListView_OnSizeChanged"> 
    <ListView.Resources> 
     <local:CategoryToGridViewConverter x:Key="CategoryToGridViewConverter" ListViewWidth="{Binding listView, Path=Width, Mode=OneWay}"/> 
    </ListView.Resources> 
    <ListView.View> 
     <Binding Path="SelectedCategory" Converter="{StaticResource CategoryToGridViewConverter}"/> 
    </ListView.View> 
</ListView> 

但問題是，ListViewWidth從未更新。它始終保持在0.但是ListView有問題顯然不是0寬度。

我在做什麼錯？

編輯：這也給輸出屏幕上綁定錯誤：

System.Windows.Data Error: 2 : Cannot find governing FrameworkElement or FrameworkContentElement for target element. BindingExpression:Path=Width; DataItem=null; target element is 'CategoryToGridViewConverter' (HashCode=33594544); target property is 'ListViewWidth' (type 'Double')

是否DependencyProperties只爲FrameworkElements工作？如果是這樣，我的轉換器怎麼會知道ListView的寬度？

Answer 1

我想你可以只使用一個多值轉換器。

<local:CategoryToGridViewMultiConverter x:Key="CategoryToGridViewConverter" /> 

轉換器：

public class CategoryToGridViewMultiConverter: IMultiValueConverter 
{ 
    public object Convert(object[] values, Type targetType, object parameter, CultureInfo culture) 
    { 
     var category = (Category)values[0]; // Assumption: you're using a class named Category 
     var listViewWidth = (double)values[1]; 

     // same logic you had before 
    } 

    public object[] ConvertBack(object value, Type[] targetTypes, object parameter, CultureInfo culture) 
    { 
     throw new NotImplementedException(); 
    } 
} 

用法：

<ListView.View> 
    <MultiBinding Converter="{StaticResource CategoryToGridViewConverter}"> 
     <Binding Path="SelectedCategory" /> 
     <Binding ElementName="listView" Path="Width" Mode="OneWay" /> 
    </MultiBinding> 
</ListView.View>