我們經(jīng)常遇到在Form下操作界面，例如由線程控制的進(jìn)度條等,，讓線程的執(zhí)行可以和Form界面融合,，不必傳進(jìn)窗體句柄,，這個(gè)時(shí)候可以用回調(diào)函數(shù)的方法來定義線程的成員函數(shù)。

      注意：原則上Delphi的多線程環(huán)境下,，對(duì)界面的輸出不能在其它線程中隨意進(jìn)行,，否則會(huì)導(dǎo)致與界面（主）線程本身的刷新操作形成沖突，導(dǎo)致一些看似無規(guī)律的問題。比較保險(xiǎn)的方式就是將要刷新的內(nèi)容通過消息或其它通信機(jī)制傳給界面線程,，由界面線程去完成實(shí)際的刷新操作,。

     所以，在我們使用回調(diào)函數(shù)把線程的可執(zhí)行代碼轉(zhuǎn)移到Tform或其他類下時(shí),，只要不是直接操作VCL控件,，一般可以參考下面代碼，可以安全執(zhí)行,。下面的代碼就是一個(gè)可以自動(dòng)執(zhí)行線程成員事件OnExecute指向的代碼片段,，你只需要給線程實(shí)例對(duì)象的OnExecute  賦值即可讓其執(zhí)行。

     用法說明：在Form下定義一個(gè)成員函數(shù)

                    TForm1= class(TForm)

                     ........

                     public

                            procedure  MyExecuteJob( AThreadSelf:TThread;var State : TJobState);

                    end;

           //實(shí)現(xiàn)部分

           procedure  TForm1.MyExecuteJob( AThreadSelf:TThread;var State : TJobState);

   在線程創(chuàng)建的時(shí)候,；即可賦值,，例如：

    var

           AutoChooseThread : TAutoChooseThread ; 

procedure Tfrm_AutoChoose.StartChooseJob;
begin
  if not Assigned(AutoChooseThread) then
  begin
     AutoChooseThread := TAutoChooseThread.Create(True);
     AutoChooseThread.OnJObComplete := OnJObComplete;
     AutoChooseThread.OnBeforeJobRun := OnBeforeJobRun;
     AutoChooseThread.OnProgress := OnProgress;
     AutoChooseThread.OnExecute := MyExecuteJob;
  end;

end;

        以上使用說明，需要完成其他回調(diào)只要按照如上方式即可,。需要注意到地方,。例如：MyExecuteJob函數(shù)

在Form1中定義了，那么傳入了兩個(gè)參數(shù),，一個(gè)是線程本身,，一個(gè)是線程狀態(tài)。如果MyExecuteJob函數(shù)中有大量循環(huán)操作,，不能立即返回,，需要不斷判斷線程狀態(tài)，如果發(fā)現(xiàn)是JsStop或JsDestroy那么就需要Exit一下,，退出函數(shù),。否則調(diào)用FreeJob();或StopJob();是不能立即奏效的。

  //線程回調(diào)函數(shù)類型定義
  TJobState = (JsStop,JsRunning,JsComplete,JsCreate,JsDestroy); //枚舉任務(wù)狀態(tài)
  TOnJObComplete = procedure (Sender : TObject) of Object; //當(dāng)完畢
  TOnJObRun = procedure(Sender:TObject) of object; //開始
  TOnProgress = procedure( MaxValue,CurValue:DWORD) of object; //進(jìn)度
  TOnExecute = procedure( AThreadSelf:TThread;var State : TJobState) of object; //任務(wù)執(zhí)行

  //自動(dòng)選擇任務(wù),，線程處理定義,，和GUI可以高度融合的方式
    TAutoChooseThread = class(TThread)
     private
        FOnJObComplete : TOnJObComplete;
        FOnJObRun   : TOnJObRun;
        FOnProgress : TOnProgress;
        FOnExecute  : TOnExecute;
        FState      : TJobState;
     public
        property OnJObComplete    : TOnJObComplete read FOnJObComplete write FOnJObComplete;
        property OnBeforeJobRun   : TOnJObRun read FOnJObRun write FOnJObRun;
        property OnProgress : TOnProgress read FOnProgress write FOnProgress;
        property OnExecute  : TOnExecute read FOnExecute write FOnExecute;
        property State      : TJobState read FState;
        procedure StartJob();
        procedure StopJob();
        procedure FreeJob();
        procedure Execute();override;
        constructor Create(isCreateSuspend:Boolean);
        destructor Destroy; override;
  end;
  
  
//線程實(shí)現(xiàn)代碼  
constructor TAutoChooseThread.Create(isCreateSuspend:Boolean);
begin
  FreeOnTerminate := True;
  FState := JsCreate;
  inherited Create(isCreateSuspend);
end;

destructor TAutoChooseThread.Destroy;
begin

  inherited;
end;

procedure TAutoChooseThread.Execute;
begin
  while not Terminated do
  begin
     //當(dāng)任務(wù)執(zhí)行前
     if Assigned( FOnJobRun ) then
     begin
        FOnJObRun(Self);
     end;

     //執(zhí)行任務(wù)
     if Assigned( FOnExecute ) then
     begin
        //執(zhí)行任務(wù)
        FState := JsRunning;
        FOnExecute(self,FState);
        //如果任務(wù)成功完成
        if FState = JsComplete then
        begin
           if Assigned(FOnJObComplete) then
           begin
              FOnJObComplete(Self);
           end;
        end;

        //如果任務(wù)銷毀
        if FState = JsDestroy then
        begin
           Exit;
        end;
     end;
     Suspend;
     Sleep(1);
  end;
end;

procedure TAutoChooseThread.FreeJob;
begin
  Terminate;
  FState := JsDestroy;
  Resume();
end;

procedure TAutoChooseThread.StartJob;
begin
  Resume();
  FState := JsRunning;
end;

procedure TAutoChooseThread.StopJob;
begin
  FState := JsStop;
end;

procedure Tfrm_AutoChoose.OnBeforeJobRun(Sender: TObject);
begin
   sGroupBox_Pocessing.Visible := True;
   sGauge1.Progress := 0;
   qry_FactorOfFlower.Close;
end;

procedure Tfrm_AutoChoose.OnExecute(AThreadSelf: TThread; var State: TJobState);
var
  MaxValue,CurValue:DWORD;
begin
  //執(zhí)行任務(wù)
  MaxValue := 1000;
  sGauge1.MaxValue := MaxValue;
  for CurValue := 0 to MaxValue - 1 do
  begin
      if TAutoChooseThread(AThreadSelf).State = JsStop then
      begin
        sGroupBox_Pocessing.Visible := False;
        sPanel_Result.Visible := False;
        qry_FactorOfFlower.Close;
        Exit;
      end;
      sGauge1.Progress := CurValue;
  end;
  State := JsComplete;
end;

procedure Tfrm_AutoChoose.OnJObComplete(Sender: TObject);
begin
  sPanel_Result.Visible := True;
end;

procedure Tfrm_AutoChoose.OnProgress(MaxValue, CurValue: DWORD);
begin

end;

procedure Tfrm_AutoChoose.FormDestroy(Sender: TObject);
begin
  inherited;
  if Assigned( AutoChooseThread ) then
  begin
     AutoChooseThread.FreeJob();
  end;
end;