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;

interface

uses
  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;

interface

uses
  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;

implementation

uses 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.