当子项是相同的对象时，在treeview中获取父注释

Question

我有一个树视图，在xaml createt树视图项中有相同的树视图。其中一个音符有一个ObservableCollection作为ItemSource。这很有魅力。但现在我希望列表中的每一项都有相同的注释（以便更好地组织）。所以我这样做：

这是列表的HierarchycalDataTemplate

<HierarchicalDataTemplate DataType="{x:Type classes:Connection}" ItemsSource="{Binding Source={StaticResource ConnectionChilds}}" >
    <TextBlock Text="{Binding DisplayName}" />
</HierarchicalDataTemplate>

和ItemsSource：

<collections:ArrayList x:Key="ConnectionChilds">
    <classes:TreeItemObject ItemsSourcePath="Child1" />
    <classes:TreeItemObject ItemsSourcePath="Child2" />
    <classes:TreeItemObject ItemsSourcePath="Child3" />
</collections:ArrayList>

TreeItemObject是一个简单的类：

public class TreeItemObject
{
    public string ItemsSourcePath { get; set; }
}

最后但并非最不重要的是TreeItemObject的HierarchycalDataTemplate：

<DataTemplate DataType="{x:Type classes:TreeItemObject}">
    <TextBlock Margin="5,0" Text="{Binding Path=ItemsSourcePath}"/>
</DataTemplate>

像这样

Connection 1
    Child1
    Child2
    Child3
Connection 2
    Child1
    Child2
    Child3
Connection 3
    Child1
    Child2
    Child3

工作顺利。但是现在如果我选择连接2\Child3，我得到了相同的对象，如连接1\Child3或连接3\Child3。好的有意义，因为基于相同的对象。在这种情况下，我没有机会在OnSseltedItemChanged上找到父注释。

因为如果我用这个扩展类搜索。我只收到第一张扩展的连接说明。

http://social.msdn.microsoft.com/Forums/silverlight/en-US/84cd3a27-6b17-48e6-8f8a-e5737601fdac/treeviewitemcontainergeneratorcontainerfromitem-returns-null?forum=silverlightnet

有没有办法在树视图中找到真正的父母？

Answer 1

很难从treeView项中获取父级，因此我所做的是，我拥有父级类型的父级的成员属性，该属性保存对父级的引用，如下所示

public class FileSystem :NotifyChange, IEnumerable
{
#region Private members
private ObservableCollection<FileSystem> subDirectoriesField;
#endregion

#region Public properties
/// <summary>
/// Gets and sets all the Files in the current folder
/// </summary>
public ObservableCollection<FileSystem> SubDirectories
{
    get
    {
        return subDirectoriesField;
    }
    set
    {
        if (subDirectoriesField != value)
        {
            subDirectoriesField = value;
            RaisePropertyChanged("SubDirectories");
        }
    }
}
/// <summary>
/// Gets or sets name of the file system 
/// </summary>
public string Name
{
    get;
    set;
}
/// <summary>
/// Gets or sets full path of the file system
/// </summary>
public string FullPath
{
    get;
    set;
}
/// <summary>
/// object of parent, null if the current node is root
/// </summary>
public FileSystem Parent
{
    get;
    set;
}
public FileSystem(string fullPath, FileSystem parent)
{
    Name = fullPath != null ? fullPath.Split(new char[] { System.IO.Path.DirectorySeparatorChar },
        StringSplitOptions.RemoveEmptyEntries).Last()
    FullPath = fullPath;
    Parent = parent;
    AddSubDirectories(fullPath);
}

public IEnumerator GetEnumerator()
{
    return SubDirectories.GetEnumerator();
}

private void AddSubDirectories(string fullPath)
{
    string[] subDirectories = Directory.GetDirectories(fullPath);
    SubDirectories = new ObservableCollection<FileSystem>();
    foreach (string directory in subDirectories)
    {
        SubDirectories.Add(new FileSystem(directory, this));
    }
}
}

我的viewModel如下所示

public class ViewModel:NotifyChange
{
  private ObservableCollection<FileSystem> directories;
  public ObservableCollection<FileSystem> Directories
  {
    get
    {
        return directoriesField;
    }
    set
    {
        directoriesField = value;
        RaisePropertyChanged("Directories");
    }
  }
  public ViewModel()
  {
   //The below code has to be moved to thread for better user expericen since when UI is loaded it might not respond for some time since it is looping through all the drives and it;s directories
   Directories=new  ObservableCollection<FileSystem>();
   Directories.Add(new FileSystem("C:\\", null);
   Directories.Add(new FileSystem("D:\\", null);
   Directories.Add(new FileSystem("E:\\", null);
  }
}

因为每个孩子都知道；现在您可以往回遍历，根节点父节点将为空

Xmal将具有以下特性

 <TreeView Grid.Row="1" Background="Transparent" ItemsSource="{Binding Directories}" Margin="0,10,0,0" Name="FolderListTreeView"
            Height="Auto" HorizontalAlignment="Stretch" Width="300"  >
            <TreeView.Resources>
                <HierarchicalDataTemplate DataType="{x:Type local:FileSystem}" ItemsSource="{Binding SubDirectories}">
                    <Label Content="{Binding Path= Name}" Name="NodeLabel" />
                </HierarchicalDataTemplate>
            </TreeView.Resources>
        </TreeView>

希望这对你有帮助

Answer 2

我认为您唯一的选择是在将子节点添加到TreeView之前克隆它们，至少允许子节点之间存在二进制差异。

如果执行此操作，则无需处理OnSseltedItemChanged事件并遍历对象图，而是向其子级中的每个子级添加父级的Weak参考。这将允许您立即引用来自孩子的父，也允许。net来正确清理对象图。

从SelectedItemChanged事件处理程序使用WeakReference属性的示例如下

private void TreeView_OnSelectedItemChanged(object sender, RoutedPropertyChangedEventArgs<object> e)
{
    var treeView = sender as TreeView;
    var item = treeView.SelectedItem as TreeItemObject;
    if (item.Parent.IsAlive)
    {
        var parent = item.Parent.Target;
    }
}

为了简洁起见，我删除了异常管理和空检查。

我希望这有帮助。

Answer 3

我个人不喜欢在转换器中创建克隆的想法，但我不知道你问题的全部范围。因此，使用您在这里展示的内容，我们可以通过多值转换器实现对每个TreeItemObject的父对象的分配。

WPF有一个很棒的特性，叫做多重绑定。它将一个或多个源值处理为单个目标。为此，它需要一个多值转换器。

因此，将TreeItemObject更改为

public class TreeItemObject
{
    public string ItemsSourcePath { get; set; }
    public WeakReference Parent { get; set; }
}

连接类型的HierarchycalDataTemplate将变为

<HierarchicalDataTemplate DataType="{x:Type classes:Connection}">
    <HierarchicalDataTemplate.ItemsSource>
        <MultiBinding Converter="{StaticResource items2Clones}">
            <Binding Source="{StaticResource ConnectionChilds}" />
            <Binding />
        </MultiBinding>
    </HierarchicalDataTemplate.ItemsSource>
    <TextBlock Text="{Binding DisplayName}" />
</HierarchicalDataTemplate>

基于上述绑定，要在转换器中设置父级，Convert中的Convert方法将如下所示

public object Convert(object[] values, Type targetType, object parameter, System.Globalization.CultureInfo culture)
{
    var destinationItems = new Collection<TreeItemObject>();

    var items = values[0] as Collection<TreeItemObject>;
    var parent = values[1] as Connection;

    // null checks are required here for items and parent

    foreach (var item in items)
    {
        var destinationItem = item.Clone(); // Assumed extension method
        destinationItem.Parent = new WeakReference(parent);
        destinationItems.Add(destinationItem);
    }

    return destinationItems;
}

最后，SseltedItemChanged事件处理程序类似于

private void TreeView_OnSelectedItemChanged(object sender, RoutedPropertyChangedEventArgs<object> e)
{
    var item = (TreeItemObject)e.NewValue;
    if ((item != null) && (item.Parent != null) && (item.Parent.IsAlive))
    {
        // do stuff - Console.WriteLine(((Connection)item.Parent.Target).DisplayName);
    }
}

为了简洁起见，我删除了异常管理和一些空检查。

我希望这有帮助