如何知道节点在Virtual TreeView中是根? [英] How to know a node is root in Virtual TreeView?

问题描述

我正在使用虚拟树状视图.有可靠的方法来知道节点是否为根节点吗?

I am using Virtual Tree View. Is there a reliable way to know if a node is root or not?

我尝试使用

if not Assigned(Node.Parent) then
  Output('This is root')
else
  Output('This is not root')

但是不起作用.

我尝试使用

if Node = tvItems.RootNode then
  Output('This is root')
else
  Output('This is not root')

但也不起作用.

推荐答案

VTV (或 VST )中的最终根节点是一个特殊的不可见节点，它充当所有用户创建的根节点(使用 parent = nil 创建的节点)的父级.通过设计，此特殊的不可见节点的 NextSibling 和 PrevSibling 属性设置为指向自身.

The ultimate root node in VTV (or VST) is a special invisible node, which acts as parent for all user created root nodes (nodes created with parent = nil). This special invisible node has by design its NextSibling and PrevSibling properties set to point to itself.

要检测某个节点是否为根节点(从用户创建的根的角度来看)，您可以例如做:

To detect whether a node is root node (in the sense of user created root) you can e.g. do:

procedure TForm16.tvItemsNodeClick(Sender: TBaseVirtualTree;
  const HitInfo: THitInfo);
begin
  if HitInfo.HitNode.Parent.NextSibling = HitInfo.HitNode.Parent then
    Caption := 'Root node'
  else
    Caption := 'Not root node';
end;

或者，如OP所述，并且不使用内部实现细节:

Alternatively, as OP commented, and without using internal implementation details:

procedure TForm16.tvItemsNodeClick(Sender: TBaseVirtualTree;
  const HitInfo: THitInfo);
begin
  if HitInfo.HitNode.Parent = Sender.RootNode then
    Caption := 'Root node'
  else
    Caption := 'Not root node';
end;

引用:TBaseVirtualTree.RootNode属性(在帮助中)

Ref: TBaseVirtualTree.RootNode Property (in Help)

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