主题:利用主线程与子线程间的消息通讯,实现任务处理队列.

目标:主线程只需发命令(消息)通知子线程需要处理的内容,而不用管任务的处理进度,可以发任意个命令,而子线程依次取出主线程交付的任务来处理.

步骤:
    1.主线程通过PostThreadMessage将命令消息发送给子线程,可以利用wParam与lParam传递需要的参数.
    2.子线程执行代码中建立一个消息循环,PeekMessage从消息队列提取消息,若无消息,则用
MsgWaitForMultipleObjects等待消息或事件对象.

示例代码:

const
  WM_TEST=WM_USER+1;
  
var
  hCloseEvent:THandle;
  ThreadID:DWORD;

type
  TTestThread=class(TThread)
  protected
    procedure Execute;override;
  end;

procedure TTestThread.Execute;
var
  msg:TMsg;
begin
  try
    while True do 
    begin
      if not PeekMessage(msg,0,0,0,PM_REMOVE) then
      begin
        case MsgWaitForMultipleObjects(1,hCloseEvent,False,INFINITE,QS_ALLINPUT) of
          WAIT_OBJECT_0: Break;
          WAIT_OBJECT_0+1:Continue;
          else Break;
        end;
      end else
      begin
        if WaitForSingleObject(hCloseEvent,0)<>WAIT_TIMEOUT then
          Break;
        if msg.hwnd<>0 then
        begin
          TranslateMessage(msg);
          DispatchMessage(msg);
          Continue;
        end else
        begin
          case msg.message of
            WM_TEST:
            begin
              //...接到主线程发过来的命令,作相应处理
              //...处理完之后,也可以用消息通知主线程
            end;
          end;
        end;
      end;  
    end;
  finally
    //...作善后處理
  end;
end;

procedure TForm1.btnCmdClick(Sender: TObject);
begin
  PostThreadMessage(ThreadID,WM_TEST,0,0);
end;

procedure TForm1.FormCreate(Sender: TObject);
begin
  hCloseEvent:=CreateEvent(nil,True,False,0);
  ThreadID:=TTestThread.Create(False).ThreadID;
end;

procedure TForm1.FormDestroy(Sender: TObject);
begin
  SetEvent(hCloseEvent);
  CloseHandle(hCloseEvent);
end;

procedure TForm1.btnStopClick(Sender: TObject);
begin
  SetEvent(hCloseEvent);
end;