如何保存IsExpanded狀態在ListView

Question

的組頭我有一個相當棘手的問題：

我使用的是ListView控件用的ItemsSource設置爲CollectionViewSource包括PropertyGroupDescription到組ListView的元素。該CollectionViewSource看起來是這樣的：

<CollectionViewSource x:Key="ListViewObjects"> 
    <CollectionViewSource.Source> 
     <Binding Path="CurrentListViewData"/> 
    </CollectionViewSource.Source> 
    <CollectionViewSource.GroupDescriptions> 
     <PropertyGroupDescription PropertyName="ObjectType" /> 
    </CollectionViewSource.GroupDescriptions> 
</CollectionViewSource> 

在我使用自定義組頭這樣的ListView控件：

<ListView.GroupStyle> 
    <GroupStyle> 
     <GroupStyle.ContainerStyle> 
     <Style TargetType="{x:Type GroupItem}"> 
      <Setter Property="Margin" Value="5"/> 
      <Setter Property="Template"> 
       <Setter.Value> 
        <ControlTemplate TargetType="{x:Type GroupItem}"> 
        <Expander IsExpanded="True"> 
         <Expander.Header> 
          <DockPanel> 
           <TextBlock Text="{Binding Path=Items[0].ObjectType /> 
          </DockPanel> 
         </Expander.Header> 
         <Expander.Content> 
          <ItemsPresenter /> 
         </Expander.Content> 
        </Expander> 
        </ControlTemplate> 
       </Setter.Value> 
      </Setter> 
     </Style> 
     </GroupStyle.ContainerStyle> 
    </GroupStyle> 
</ListView.GroupStyle> 

正如你可以看到擴展的IsExpanded屬性設置爲true。這意味着每當ListView刷新時，所有Expander控件都被展開。

但是我確實想保存每個擴展器的最後一個狀態。我一直無法找到一種方法來保存每個ObjectType的擴展器狀態列表。我正在試驗一個綁定的HashTable和一個Converter，但是我沒有提供ObjectType作爲ConverterParameter，因爲它總是作爲一個字符串傳遞的。但這可能不是解決方案。

有人可以給我一個提示或解決方案的想法嗎？ :)

Answer 1

您可以創建一個新的類字典（比如，對象類型列爲重點bool的值），並給它一個索引：

Dictionary<ObjectType, bool> expandStates = new Dictionary<ObjectType, bool>(); 

    public bool this[ObjectType key] 
    { 
     get 
     { 
      if (!expandStates.ContainsKey(key)) return false; 
      return expandStates[key]; 
     } 
     set 
     { 
      expandStates[key] = value; 
     } 
    } 

然後，在某個地方ResourceDictionary中，並結合實例化它在IsExpanded它是這樣的：

<Expander IsExpanded="{Binding Source={StaticResource myExpMgr}, Path=[Items[0].ObjectType]}"> 

這很可能做到這一點：讓WPF打電話給你的代碼，並通過只是當你需要它的參數的一個很好的方式。 （WPF讓你把索引器中的子表達式放在一個綁定路徑中對我來說是新聞 - 雖然不是好事！）

Answer 2

接受的答案是錯誤的，正如評論中所解釋的那樣。我寫了下面的行爲，達到了預期的功能：

public class PersistGroupExpandedStateBehavior : Behavior<Expander> 
{ 
    #region Static Fields 

    public static readonly DependencyProperty GroupNameProperty = DependencyProperty.Register(
     "GroupName", 
     typeof(object), 
     typeof(PersistGroupExpandedStateBehavior), 
     new PropertyMetadata(default(object))); 

    private static readonly DependencyProperty ExpandedStateStoreProperty = 
     DependencyProperty.RegisterAttached(
      "ExpandedStateStore", 
      typeof(IDictionary<object, bool>), 
      typeof(PersistGroupExpandedStateBehavior), 
      new PropertyMetadata(default(IDictionary<object, bool>))); 

    #endregion 

    #region Public Properties 

    public object GroupName 
    { 
     get 
     { 
      return (object)this.GetValue(GroupNameProperty); 
     } 

     set 
     { 
      this.SetValue(GroupNameProperty, value); 
     } 
    } 

    #endregion 

    #region Methods 

    protected override void OnAttached() 
    { 
     base.OnAttached(); 

     bool? expanded = this.GetExpandedState(); 

     if (expanded != null) 
     { 
      this.AssociatedObject.IsExpanded = expanded.Value; 
     } 

     this.AssociatedObject.Expanded += this.OnExpanded; 
     this.AssociatedObject.Collapsed += this.OnCollapsed; 
    } 

    protected override void OnDetaching() 
    { 
     this.AssociatedObject.Expanded -= this.OnExpanded; 
     this.AssociatedObject.Collapsed -= this.OnCollapsed; 

     base.OnDetaching(); 
    } 

    private ItemsControl FindItemsControl() 
    { 
     DependencyObject current = this.AssociatedObject; 

     while (current != null && !(current is ItemsControl)) 
     { 
      current = VisualTreeHelper.GetParent(current); 
     } 

     if (current == null) 
     { 
      return null; 
     } 

     return current as ItemsControl; 
    } 

    private bool? GetExpandedState() 
    { 
     var dict = this.GetExpandedStateStore(); 

     if (!dict.ContainsKey(this.GroupName)) 
     { 
      return null; 
     } 

     return dict[this.GroupName]; 
    } 

    private IDictionary<object, bool> GetExpandedStateStore() 
    { 
     ItemsControl itemsControl = this.FindItemsControl(); 

     if (itemsControl == null) 
     { 
      throw new Exception(
       "Behavior needs to be attached to an Expander that is contained inside an ItemsControl"); 
     } 

     var dict = (IDictionary<object, bool>)itemsControl.GetValue(ExpandedStateStoreProperty); 

     if (dict == null) 
     { 
      dict = new Dictionary<object, bool>(); 
      itemsControl.SetValue(ExpandedStateStoreProperty, dict); 
     } 

     return dict; 
    } 

    private void OnCollapsed(object sender, RoutedEventArgs e) 
    { 
     this.SetExpanded(false); 
    } 

    private void OnExpanded(object sender, RoutedEventArgs e) 
    { 
     this.SetExpanded(true); 
    } 

    private void SetExpanded(bool expanded) 
    { 
     var dict = this.GetExpandedStateStore(); 

     dict[this.GroupName] = expanded; 
    } 

    #endregion 
} 

它附加一個字典含有ItemsControl節省展開狀態爲每個組項目。即使控件中的項目發生更改，這也會持續。

用法：

<Expander> 
    <i:Interaction.Behaviors> 
     <behaviors:PersistGroupExpandedStateBehavior GroupName="{Binding Name}" /> 
    </i:Interaction.Behaviors> 
    ... 
</Expander> 

Answer 3

的顯着回答沒有在.NET 4.5的工作。

這樣做的一個簡單的解決方案是將

private bool _isExpanded = true; 
    public bool IsExpanded 
    { 
     get { return _isExpanded; } 
     set { _isExpanded = value; } 
    } 

屬性添加到您的視圖模型（在這種情況下，無論對象CurrentListViewData持有）

然後執行：

<Expander IsExpanded="{Binding Items[0].IsExpanded}"> 

您模板。

簡單而有效就像WPF應該是