Question

我实际上有一个类似于TreeView的自定义UserControl。它唯一缺少的是来自TreeView的CollapseAll()方法，因此我要求a）找到CollapseAll方法的源代码，以便我可以复制它，或者b）手动（并递归地）遍历所选节点的所有子节点并折叠它们。

这是我当前的崩溃方法：

private void OnNodeCollapsed(TreeNode node) {
    foreach(FileSystemNode n in node.Nodes) {
        if(n.NodeType != FileSystemNodeType.Computer && n.NodeType != FileSystemNodeType.Drive) {
            if(n.Nodes.Count > 0) {
                n.Nodes.Clear();
            }
        }
    }

    foreach(TreeNode child in node.Nodes) {
        // and this is where I lose it
    }
}

我只想折叠子节点，而不是整个树。有没有办法做到这一点？

这是一个很好的解决方案：Recursion with yield return elements order in tree。

Answer 1

您可以为自定义控件添加这样的扩展名，并使用以下展开/折叠方法

public static class TreeViewExt
{
     public static void ExpandRecursively(this ItemsControl itemsControl, bool expand, int levelDepth)
    {
        int depth = levelDepth == int.MaxValue ? levelDepth : levelDepth - 1;
       TreeViewItem treeViewItem = itemsControl as TreeViewItem;
        if (treeViewItem != null)
            treeViewItem.IsExpanded = expand || levelDepth >= 0; // expand, or keep expanded when levelDepth >= 0
         if (levelDepth > 0 || !expand)
        {
            // get container generator of itemsControl
            ItemContainerGenerator itemContainerGenerator = itemsControl.ItemContainerGenerator;
             // if containers have already been generated, the subItems can be expanded/collapsed
            if (itemContainerGenerator.Status == GeneratorStatus.ContainersGenerated)
            {
                for (int i = itemsControl.Items.Count - 1; i >= 0; --i)
                {
                    ItemsControl childControl = itemContainerGenerator.ContainerFromIndex(i) as ItemsControl;
                    if (childControl != null)
                        childControl.ExpandRecursively(expand, depth);
                }
            } 
            else
            {
                EventHandler handler = null; // store in variable, so the handler can be detached
                handler = new EventHandler((s, e) =>
                {
                    if (itemContainerGenerator.Status == GeneratorStatus.ContainersGenerated)
                    {
                        for (int i = itemsControl.Items.Count - 1; i >= 0; --i)
                        {
                            ItemsControl childControl = itemContainerGenerator.ContainerFromIndex(i) as ItemsControl;
                            if (childControl != null)
                                childControl.ExpandRecursively(expand, depth);
                            itemContainerGenerator.StatusChanged -= handler; // detach
                        }
                    }
                });
                itemContainerGenerator.StatusChanged += handler; // attach
            }
        }
    }
}

完整代码：Treeview Recursive Expand/Collapse

修改

由于OP想要为WinForm UserControl执行此操作，您可以使用这样的方法遍历子控件，

private IEnumerable<Node> getAllNodesRecursively(Node subnode) { // Return the parent before its children yield return subnode; foreach (Node node in subnode.Nodes) { foreach(Node n in getAllNodesRecursively(node)) { yield return n; } } }

Recursion with yield return elements order in tree

递归地折叠自定义UserControl中父节点的所有子节点

1 个答案: