线程！线程！！线程！！！(Delphi版)

以下内容仅供初学者参考

看到有的同学对Delphi的线程认识不够深，特开一贴给同学们讲讲。

主要给出两种常用的线程形式。

1、长等待型线程示例，等待命令，执行不定长的工作，但每个工作的时间不会太长。
2、长工作型线程示例，执行一个很长时间的工作，但可以很快响应取消操作。

注：对于在线程中取消存储过程的执行仍然无解

以下程序所用的知识为:消息机制以及常用的API函数


主程序Unit1

Delphi(Pascal) code

unit Unit1;interfaceuses  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,  Dialogs, StdCtrls,LongWaitTrd;type  TForm1 = class(TForm)    btnSetTask: TButton;    btnExitThd: TButton;    btnCreateTrd: TButton;    procedure btnSetTaskClick(Sender: TObject);    procedure btnCreateTrdClick(Sender: TObject);    procedure btnExitThdClick(Sender: TObject);  private     LongWaitThread:TLongWaitTrd;     procedure OnThreadMessage(var Message: TMessage); message WM_USER+2000;  public    { Public declarations }  end;var  Form1: TForm1;implementation{$R *.dfm}procedure TForm1.btnSetTaskClick(Sender: TObject);begin   if (LongWaitThread<>nil) then   PostThreadMessage(LongWaitThread.ThreadID,WM_USER+1000,0,0);end;procedure TForm1.btnCreateTrdClick(Sender: TObject);begin  LongWaitThread:=TLongWaitTrd.Create(true);  LongWaitThread.MainWin:=Handle;  LongWaitThread.Resume;end;procedure TForm1.OnThreadMessage(var Message: TMessage);begin  if Message.Msg= WM_USER+2000 then  begin    Showmessage(String(message.LParam));  end;end;procedure TForm1.btnExitThdClick(Sender: TObject);begin    if (LongWaitThread<>nil) then    begin      if (not LongWaitThread.ExitLongWaitTrd()) then      ShowMessage('The thread exited time out');    end;end;end.

线程类：

Delphi(Pascal) code

unit LongWaitTrd;interfaceuses  Classes,Windows,Messages,SyncObjs;type  TLongWaitTrd = class(TThread)  private    FMainWin:THandle;    QuitEvent: TEvent;    procedure  SendFeedBackToMainWin();    procedure  DoTheHardWork();      protected    procedure Execute; override;  public    constructor  Create(CreateSuspended: Boolean);    destructor   Destroy; override;    function  ExitLongWaitTrd():Boolean;  published    property MainWin:THandle read FMainWin write FMainWin;  end;implementationuses Unit1;constructor TLongWaitTrd.Create(CreateSuspended: Boolean);begin  inherited Create(CreateSuspended);end;destructor TLongWaitTrd.Destroy;begin  inherited;end;procedure TLongWaitTrd.DoTheHardWork();begin    //to do end;procedure TLongWaitTrd.Execute;var    Msg: TMsg;begin  FreeOnTerminate:=True;//1.长等待型线程示例//  while GetMessage(Msg, 0, 0, 0) do  //  begin//     if (Msg.message=WM_USER+1000) then //任务来了//     begin//        DoTheHardWork();//        SendFeedBackToMainWin;//     end;//     if (Msg.message=WM_QUIT) then//     begin//        QuitEvent.SetEvent;//        Break;//     end;//  end;//2.长工作型线程示例//   while(true) do//   begin//     if  PeekMessage(Msg, 0, 0, 0, PM_REMOVE) then//     begin//        if (Msg.message=WM_QUIT) then//        begin//          QuitEvent.SetEvent;//          Break;//        end;//     end;//     DoTheHardWork();//   end;   end;function TLongWaitTrd.ExitLongWaitTrd;begin  Result:=true;  QuitEvent:=TEvent.Create(nil,True,False,'QuitEvent');  PostThreadMessage(ThreadID,WM_QUIT,0,0);  if  (QuitEvent.WaitFor(2000)=wrTimeOut) then       Result:=false;  QuitEvent.Free ;   end;procedure TLongWaitTrd.SendFeedBackToMainWin();var  Status:String;begin   if (MainWin<>0) then   begin     Status:='The data has been processed by thread.';     PostMessage(MainWin,WM_USER+2000,0,Integer(Status))   end;   end;end.