线程怎么终止不了呢？大家帮我看看代码！谢谢！！

Question

unit Unit1;interfaceuses
  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
  Dialogs, StdCtrls,unit2, ComCtrls;type
  TForm1 = class(TForm)
    Button1: TButton;
    Button2: TButton;
    pb2: TProgressBar;
    pb1: TProgressBar;
    Button3: TButton;    procedure Button1Click(Sender: TObject);
    procedure Button2Click(Sender: TObject);
    procedure Button3Click(Sender: TObject);
  private
    pb1Thread:TMyThread;
    pb2Thread:TMyThread;
    { Private declarations }
  public
    { Public declarations }
  end;var
  Form1: TForm1;implementation{$R *.dfm}procedure TForm1.Button1Click(Sender: TObject);
begin
  pb1Thread:=TMyThread.Create(true);
  pb1Thread.FreeOnTerminate:=true;
  pb1Thread.pbID:=1;
  pb1Thread.Resume;
end;procedure TForm1.Button2Click(Sender: TObject);
begin
  pb1Thread:=TMyThread.Create(true);
  pb1Thread.FreeOnTerminate:=true;
  pb1Thread.pbID:=2;
  pb1Thread.Resume;
end;procedure TForm1.Button3Click(Sender: TObject);
begin
  pb1Thread.Terminate;
end;end.
/////////////////////////////////////////////////////////////
线程单元：
unit Unit2;interfaceuses
  Classes;type
  TMyThread = class(TThread)
  private
    { Private declarations }
  protected
    procedure Execute; override;
    procedure StepProgress;
  public
    pbID:1..2;
  end;implementation
uses Unit1;
{ Important: Methods and properties of objects in VCL or CLX can only be used
  in a method called using Synchronize, for example,      Synchronize(UpdateCaption);  and UpdateCaption could look like,    procedure TMyThread.UpdateCaption;
    begin
      Form1.Caption := 'Updated in a thread';
    end; }{ TMyThread }procedure TMyThread.Execute;
var
  i:cardinal;
begin
  i:=1;
  while (i<100000) do
  begin
    synchronize(stepprogress);
    Inc(i);
  end;
end;procedure TMyThread.StepProgress;
begin
  if pbID=1 then Form1.pb1.StepIt
  else Form1.pb2.StepIt;
end;end运行的时候，我先点击button1，启动pb1Thread线程，然后点击button3，企图终止pb1Thread，但是程序似乎没有理我，滚动条依然闪个不停，怎么回事？
希望能得到你的帮助！
谢谢！

Answer 1

procedure TMyThread.Execute;
var
  i:cardinal;
begin
  i:=1;
  while (i<100000) do
  begin
    synchronize(stepprogress);
    Inc(i);
    if Terminated then Exit; //<<--
  end;
end;

Answer 2

procedure TMyThread.Execute;
var
  i:cardinal;
begin
  i:=1;
  while (i<100000) do
  begin
    if self.Terminated then
      Break;
    synchronize(stepprogress);
    Inc(i);
  end;
end;

Answer 3

同楼上2位意见，循环里要加个Terminated判断

Answer 4

还有你的button2里的代码自己要看着改改数字！呵呵！