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interface

uses
  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
  Dialogs, StdCtrls, Buttons;

type
  TForm1 = class(TForm)
    UsedThread: TBitBtn;
    NoUsedThread: TBitBtn;
    procedure UsedThreadClick(Sender: TObject);
    procedure NoUsedThreadClick(Sender: TObject);
  private
    { Private declarations }
  public
    { Public declarations }
  end;

var
  Form1: TForm1;

implementation

{$R *.dfm}

function MyThreadFunc(P:pointer):Longint;stdcall;
var
  i:longint;
  DC:HDC;
  S:string;
begin
  DC:=GetDC(Form1.Handle);
  for i:=0 to 500000 do begin
    S:=Inttostr(i);
    Textout(DC,10,10,Pchar(S),length(S));
  end;
  ReleaseDC(Form1.Handle,DC);
end;

procedure TForm1.UsedThreadClick(Sender: TObject);
var
  hThread:Thandle;//定义一个句柄
  ThreadID:DWord;
begin
//创建线程，同时线程函数被调用
  hthread:=CreateThread(nil,0,@MyThreadfunc,nil,0,ThreadID);
  if hThread=0 then
  messagebox(Handle,'Didn’tCreateaThread',nil,MB_OK);
end;

procedure TForm1.NoUsedThreadClick(Sender: TObject);
begin
  MyThreadfunc(nil);
  //没有创建线程时，直接调用线程函数
end;
end.