Specific examples of the tree structure to achieve Delphi

unit Unit1;
interface
uses
  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
  Dialogs, StdCtrls, ComCtrls, DB, ADODB;
type
  PNodeInfoEx = ^TNodeInfoEx;
  TNodeInfoEx = Packed Record
      NodeID    : Integer;
      ParentID  : Integer;
      NodeType  : Integer;
      ChnNodeTitle : String;
      ImageIndex: SmallInt;
      SelectedIndex: SmallInt;
   end;
  TForm1 = class(TForm)
    tv1: TTreeView;
    btn1: TButton;
    qry1: TADOQuery;
    procedure btn1Click(Sender: TObject);
    procedure FormDestroy(Sender: TObject);
  private
    { Private declarations }
    function StaticBuildTree(TreeView:TTreeView ):Boolean;
    function AddTreeItem(TreeView:TTreeView; AddNodeInfo:PNodeInfoEx):TTreeNode;
    function FindTreeItem(TreeView:TTreeView; CurNodeID:integer): TTreeNode;
  public
    { Public declarations }
  end;
var
  Form1: TForm1;
implementation
{$R *.dfm}

function TForm1.StaticBuildTree(TreeView:TTreeView ):Boolean;
var
  AddNodeInfo: PNodeInfoEx; 
the begin 
  the Result: = False; 
  qry1.LoadFromFile ( ' c: /AdminixTree.xml ' ); // here to XML file as a data source 
  Treeview.Items.BeginUpdate; // Remember: Before adding bulk data to use BeginUpdate, to temporarily close certain events triggered by the addition of data (such as OnChange events, etc.) 
  Treeview.Items.Clear; // Clear Treeview 
  the try 
    the try 
      IF qry1.RecordCount> 0  the then 
        the begin 
          qry1.First; 
          the while Not qry1 .EOF do 
          the begin 
            New (AddNodeInfo); // generating structure 
            AddNodeInfo ^ .NodeID: = qry1.FieldByName ('NODE_ID').AsInteger;
            AddNodeInfo^.ParentID := qry1.FieldByName('PARENT_ID').AsInteger;
            AddNodeInfo^.NodeType := qry1.FieldByName('NodeType').AsInteger;
            AddNodeInfo^.ChnNodeTitle := qry1.FieldByName('ChnNodeTitle').AsString;
            AddNodeInfo^.ImageIndex := qry1.FieldByName('ImageIndex').AsInteger;
            AddNodeInfo^.SelectedIndex := qry1.FieldByName('SelectedIndex') .AsInteger; 
            AddTreeItem (Treeview, AddNodeInfo); // pointer to structure stored in Treeview 
            qry1.Next;
           End ;
         End ;
     the except 
      Application.MessageBox ( ' spanning tree node failure ' , MB_ICONSTOP + MB_OK);
       The raise ; / / abnormality superior throwing 
    End ; 
    qry1.Close; 
    the Result: = True;
   the finally 
    Treeview.Items.EndUpdate; 
  End ;
 End ;
 // when joining node, should be added is determined parent node or a child node, it is determined ParentID is based on the presence or absence of the node in the tree nodes existing in 
function TForm1.AddTreeItem(TreeView:TTreeView; AddNodeInfo:PNodeInfoEx):TTreeNode;
var
    ParentNode: TTreeNode;
begin
    ParentNode := FindTreeItem(Treeview,AddNodeInfo^.ParentID);
    If ParentNode <> nil then
        Result := Treeview.Items.AddChildObject(ParentNode, Trim(AddNodeInfo.ChnNodeTitle), Pointer(AddNodeInfo))
    else
        Result := Treeview.Items.AddObject(ParentNode, Trim(AddNodeInfo.ChnNodeTitle), Pointer(AddNodeInfo));
    if Result<>nil then
    begin
        Result.ImageIndex    := AddNodeInfo.ImageIndex;
        Result.SelectedIndex: = AddNodeInfo.SelectedIndex;
     End ;
 End ;
 // this is determined whether there is a parent node 
function TForm1.FindTreeItem (the TreeView: TTreeView; CURNODEID: Integer): TTreeNode;
 var 
    I: Integer; 
the begin 
  the Result: = nil ;
   for I: = 0  to Treeview.Items.Count- . 1  do 
  the begin 
      IF CURNODEID = PNodeInfoEx (Treeview.Items [I] .Data) ^ NodeID. the then 
      the begin 
          the Result: = Treeview.Items [I]; 
          the Exit; 
      End ;
  End ;
 End ;
 // tree structure 
Procedure TForm1.btn1Click (Sender: TObject);
 the begin 
   StaticBuildTree (TV1) 
End ;
 // when the form releasing structure pointers to nodes in the tree must take to relieve, for the Why should Dispose casts after release, before a special explanation, this is not tired 
Procedure TForm1.FormDestroy (Sender: TObject);
 var 
    I: Integer; 
the begin 
  for I: = 0  to tv1.Items.Count- . 1  do 
  the begin 
       the Dispose (PNodeInfoEx (tv1.Items [i] .Data)) 
  End ;
 End ;
 End . 





// how to access the tree node? 
procedure TForm1.tv1MouseDown(Sender: TObject; Button: TMouseButton;
  Shift: TShiftState; X, Y: Integer);
var
  pNode:TTreeNode;
begin
  pNode:=tv1.GetNodeAt(x,y);
  if (pNode<>nil) and  (Button=mbleft) then
   ShowMessage(PNodeInfoEx(pNode.Data)^.ChnNodeTitle);
end;