说明:

SendMessage

//*************************   窗体文件  *******************************

unit Main;

interface

uses
  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
  Dialogs,MyThread, StdCtrls;
const
  WM_MYQUIT=WM_USER+101;
type
  TForm1 = class(TForm)
    Label1: TLabel;
    Button1: TButton;
    procedure FormCreate(Sender: TObject);
    procedure Button1Click(Sender: TObject);
  private
    { Private declarations }
    FThread:TMyThread;
  public
    { Public declarations }

procedure MyQuit(var Msg:TMessage);message WM_MYQUIT;
  end;

var
  Form1: TForm1;

implementation

{$R *.dfm}

{ TForm1 }

procedure TForm1.Button1Click(Sender: TObject);
begin
  if Assigned(FThread) then
    showmessage('存在')
  else
    showmessage('不存在');
end;

procedure TForm1.FormCreate(Sender: TObject);
begin
  FThread:=TMyThread.Create(False);
end;

procedure TForm1.MyQuit(var Msg: TMessage);
var
  BeginTime:DWORD;
begin
  BeginTime:=GetTickCount;
  if Assigned(FThread) then
  begin
    FThread.Terminate;
    if FThread.Suspended then
      FThread.Resume;

//  如果线程使用SendMessage发送消息后
    //  则 FThread.WaitFor;  线程将一直等待下去，
    //  原因是:SendMessage一直在等待窗口程序处理完消息再返回 ,程序将出现一直等待，直到主线程退出
    FThread.WaitFor;  //  程序一直等待 直到线程退出
    FThread.Free;
    FThread:=nil;
  end;
  Label1.Caption:='运行时间: '+intTostr(GetTickCount-BeginTime);
end;

end.

//  *****************************   下面是简单的线程类，主要用于给主窗体发送消息，通知结束线程  ************

unit MyThread;

interface

uses
  Classes,windows,Messages;

type
  TMyThread = class(TThread)
  private
    { Private declarations }
  protected
    procedure Execute; override;
  end;

implementation

uses Main;

{ Important: Methods and properties of objects in visual components can only be
  used in a method called using Synchronize, for example,

Synchronize(UpdateCaption);

and UpdateCaption could look like,

procedure MyThread.UpdateCaption;
    begin
      Form1.Caption := 'Updated in a thread';
    end; }

{ TMyThread }

procedure TMyThread.Execute;
begin
  // 发送消息给主窗口，通知结束该线程
  // SendMessage(Form1.Handle,WM_MYQUIT,0,0);

PostMessage(Form1.Handle,WM_MYQUIT,0,0);

end;

end.