Delphi自定义TTreeNode

我正在尝试创建我的自定义TTreeNode类

比如说

TCustomTreeNode = class(TTreeNode)
  private
  public
    Comment:string;
  end;

我在树状视图中创建并添加节点，如下所示：

var
  NewCustomTreeNode:TCustomTreeNode;
begin
  NewCustomTreeNode:= TCustomTreeNode.Create(TreeView.Items);
  NewCustomTreeNode.Comment:='blqblq';
  TreeView.Items.AddChild(NewCustomTreeNode,'NodeText');

TCustomTreeNode(TreeNode).Comment:='asdadssadas';

当我尝试访问自定义创建的树节点时，会弹出错误。例如，我确实喜欢这样：

var
  NewCustomTreeNode:TCustomTreeNode;
begin
  NewCustomTreeNode:= TCustomTreeNode.Create(TreeView.Items);
  NewCustomTreeNode.Comment:='blqblq';
  TreeView.Items.AddChild(NewCustomTreeNode,'NodeText');

TCustomTreeNode(TreeNode).Comment:='asdadssadas';

---

plase help

代码的问题是调用

AddChild

会导致树视图创建新节点。由于您没有告诉树视图创建子类的节点，因此它创建了一个普通的

treenode

。然后，当你试图将它转换为一个

TCustomTreeNode

，世界就结束了

您需要使用

OnCreateNodeClass

方法来确保树视图能够创建新节点。像这样：

type
  TCustomTreeNode = class(TTreeNode)
  protected
    procedure Assign(Source: TPersistent); override;
  public
    Comment: string;
  end;

procedure TCustomTreeNode.Assign(Source: TPersistent);
begin
  if Source is TCustomTreeNode then
    Comment := TCustomTreeNode(Source).Comment;
  inherited;
end;


procedure TForm1.FormCreate(Sender: TObject);
var
  NewNode: TCustomTreeNode;
begin
  NewNode := TreeView1.Items.Add(nil, 'Node1') as TCustomTreeNode;
  NewNode.Comment := 'A comment';
  NewNode := TreeView1.Items.Add(nil, 'Node2') as TCustomTreeNode;
  NewNode.Comment := 'Another comment';
end;

procedure TForm1.TreeView1Click(Sender: TObject);
var
  Node: TCustomTreeNode;
begin
  Node := TreeView1.Selected as TCustomTreeNode;
  if Assigned(Node) then
    ShowMessage(Node.Comment);
end;

procedure TForm1.TreeView1CreateNodeClass(Sender: TCustomTreeView; var NodeClass: TTreeNodeClass);
begin
  NodeClass := TCustomTreeNode;
end;

我不能说自己是世界上最伟大的Delphi树视图专家，但以我的经验，你从来没有自己创建过树节点。您应该始终调用

t预览.Items

上的

AddXXX

方法之一来创建新节点