在delphi线程中实现消息循环

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转载最新推荐文章于 2026-06-02 22:16:06 发布 284 阅读 AI 写同款· GEO 优化 ›

Delphi的TThread类使用很方便,但是有时候我们需要在线程类中使用消息循环,delphi没有提供.花了两天的事件研究了一下win32的消息系统,写了一个线程内消息循环的测试.但是没有具体应用过,贴出来给有这方面需求的DFW参考一下.
希望大家和我讨论.

{-----------------------------------------------------------------------------
Unit Name: uMsgThread
Author: xwing
eMail : xwing@263.net ; MSN : xwing1979@hotmail.com
Purpose: Thread with message Loop
History:

2003-6-19, add function to Send Thread Message. ver 1.0
use Event List and waitforsingleObject
your can use WindowMessage or ThreadMessage
2003-6-18, Change to create a window to Recving message
2003-6-17, Begin.
-----------------------------------------------------------------------------}
unit uMsgThread;

interface
{$WARN SYMBOL_DEPRECATED OFF}
{$DEFINE USE_WINDOW_MESSAGE}
uses
Classes, windows, messages, forms, sysutils;

type
TMsgThread = class(TThread)
private
{$IFDEF USE_WINDOW_MESSAGE}
FWinName : string;
FMSGWin : HWND;
{$ELSE}
FEventList : TList;
FCtlSect : TRTLCriticalSection;
{$ENDIF}
FException : Exception;
fDoLoop : Boolean;
FWaitHandle : THandle;
{$IFDEF USE_WINDOW_MESSAGE}
procedure MSGWinProc(var Message: TMessage);
{$ELSE}
procedure ClearSendMsgEvent;
{$ENDIF}
procedure SetDoLoop(const Value: Boolean);
procedure WaitTerminate;

protected
Msg :tagMSG;

procedure Execute; override;
procedure HandleException;
procedure DoHandleException;virtual;
//Inherited the Method to process your own Message
procedure DoProcessMsg(var Msg:TMessage);virtual;
//if DoLoop = true then loop this procedure
//Your can use the method to do some work needed loop.
procedure DoMsgLoop;virtual;
//Initialize Thread before begin message loop
procedure DoInit;virtual;
procedure DoUnInit;virtual;

procedure PostMsg(Msg:Cardinal;wParam:Integer;lParam:Integer);
//When Use SendMsg method Must not use Synchronize Method in ThreadLoop !!!
//otherwise will caurse DeadLock
procedure SendMsg(Msg:Cardinal;wParam:Integer;lParam:Integer);

public
constructor Create(Loop:Boolean=False;ThreadName: string='');
destructor destroy;override;
procedure AfterConstruction;override;

//postMessage to Quit,and Free(if FreeOnTerminater = true)
//can call this in thread loop, don't use terminate property.
procedure QuitThread;
//PostMessage to Quit and Wait, only call in MAIN THREAD
procedure QuitThreadWait;
//just like Application.processmessage.
procedure ProcessMessage;
//enable thread loop, no waitfor message
property DoLoop: Boolean read fDoLoop Write SetDoLoop;

end;

implementation

{ TMsgThread }
{//////////////////////////////////////////////////////////////////////////////}
constructor TMsgThread.Create(Loop:Boolean;ThreadName:string);
begin
{$IFDEF USE_WINDOW_MESSAGE}
if ThreadName <> '' then
FWinName := ThreadName
else
FWinName := 'Thread Window';
{$ELSE}
FEventList := TList.Create;
InitializeCriticalSection(fCtlSect);
{$ENDIF}

FWaitHandle := CreateEvent(nil, True, False, nil);

FDoLoop := Loop; //default disable thread loop
inherited Create(False); //Create thread
FreeOnTerminate := True; //Thread quit and free object

//Call resume Method in Constructor Method
Resume;
//Wait until thread Message Loop started
WaitForSingleObject(FWaitHandle,INFINITE);
end;

{------------------------------------------------------------------------------}
procedure TMsgThread.AfterConstruction;
begin
end;

{------------------------------------------------------------------------------}
destructor TMsgThread.destroy;
begin
{$IFDEF USE_WINDOW_MESSAGE}
{$ELSE}
FEventList.Free;
DeleteCriticalSection(FCtlSect);
{$ENDIF}

inherited;
end;

{//////////////////////////////////////////////////////////////////////////////}
procedure TMsgThread.Execute;
var
mRet:Boolean;
aRet:Boolean;
{$IFNDEF USE_WINDOW_MESSAGE}
uMsg:TMessage;
{$ENDIF}
begin
{$IFDEF USE_WINDOW_MESSAGE}
FMSGWin := CreateWindow('STATIC',PChar(FWinName),WS_POPUP,0,0,0,0,0,0,hInstance,nil);
SetWindowLong(FMSGWin, GWL_WNDPROC, Longint(MakeObjectInstance(MSGWinProc)));
{$ELSE}
PeekMessage(Msg,0,WM_USER,WM_USER,PM_NOREMOVE); //Force system alloc a msgQueue
{$ENDIF}

//notify Conctructor can returen.
SetEvent(FWaitHandle);
CloseHandle(FWaitHandle);

mRet := True;
try
DoInit;
while mRet do //Message Loop
begin
if fDoLoop then
begin
aRet := PeekMessage(Msg,0,0,0,PM_REMOVE);
if aRet and (Msg.message <> WM_QUIT) then
begin
{$IFDEF USE_WINDOW_MESSAGE}
TranslateMessage(Msg);
DispatchMessage(Msg);
{$ELSE}
uMsg.Msg := Msg.message;
uMsg.wParam := Msg.wParam;
uMsg.lParam := Msg.lParam;
DoProcessMsg(uMsg);
{$ENDIF}

if Msg.message = WM_QUIT then
mRet := False;
end;
{$IFNDEF USE_WINDOW_MESSAGE}
ClearSendMsgEvent; //Clear SendMessage Event
{$ENDIF}
DoMsgLoop;
end
else begin
mRet := GetMessage(Msg,0,0,0);
if mRet then
begin
{$IFDEF USE_WINDOW_MESSAGE}
TranslateMessage(Msg);
DispatchMessage(Msg);
{$ELSE}
uMsg.Msg := Msg.message;
uMsg.wParam := Msg.wParam;
uMsg.lParam := Msg.lParam;
DoProcessMsg(uMsg);
ClearSendMsgEvent; //Clear SendMessage Event
{$ENDIF}
end;
end;
end;
DoUnInit;
{$IFDEF USE_WINDOW_MESSAGE}
DestroyWindow(FMSGWin);
FreeObjectInstance(Pointer(GetWindowLong(FMSGWin, GWL_WNDPROC)));
{$ENDIF}
except
HandleException;
end;
end;

{------------------------------------------------------------------------------}
{$IFNDEF USE_WINDOW_MESSAGE}
procedure TMsgThread.ClearSendMsgEvent;
var
aEvent:PHandle;
begin
EnterCriticalSection(FCtlSect);
try
if FEventList.Count <> 0 then
begin
aEvent := FEventList.Items[0];
if aEvent <> nil then
begin
SetEvent(aEvent^);
CloseHandle(aEvent^);
Dispose(aEvent);
end;
FEventList.Delete(0);
end;
finally
LeaveCriticalSection(FCtlSect);
end;
end;
{$ENDIF}

{------------------------------------------------------------------------------}
procedure TMsgThread.HandleException;
begin
FException := Exception(ExceptObject); //Get Current Exception object
try
if not (FException is EAbort) then
inherited Synchronize(DoHandleException);
finally
FException := nil;
end;
end;

{------------------------------------------------------------------------------}
procedure TMsgThread.DoHandleException;
begin
if FException is Exception then
Application.ShowException(FException)
else
SysUtils.ShowException(FException, nil);
end;

{//////////////////////////////////////////////////////////////////////////////}
{$IFDEF USE_WINDOW_MESSAGE}
procedure TMsgThread.MSGWinProc(var Message: TMessage);
begin
DoProcessMsg(Message);
with Message do
Result:=DefWindowProc(FMSGWin,Msg,wParam,lParam);
end;
{$ENDIF}

{------------------------------------------------------------------------------}
procedure TMsgThread.DoProcessMsg(var Msg:TMessage);
begin
end;

{------------------------------------------------------------------------------}
procedure TMsgThread.ProcessMessage;
{$IFNDEF USE_WINDOW_MESSAGE}
var
uMsg:TMessage;
{$ENDIF}
begin
while PeekMessage(Msg,0,0,0,PM_REMOVE) do
if Msg.message <> WM_QUIT then
begin
{$IFDEF USE_WINDOW_MESSAGE}
TranslateMessage(Msg);
DispatchMessage(msg);
{$ELSE}
uMsg.Msg := Msg.message;
uMsg.wParam := Msg.wParam;
uMsg.lParam := Msg.lParam;
DoProcessMsg(uMsg);
{$ENDIF}
end;
end;

{//////////////////////////////////////////////////////////////////////////////}
procedure TMsgThread.DoInit;
begin
end;

procedure TMsgThread.DoUnInit;
begin
end;

procedure TMsgThread.DoMsgLoop;
begin
Sleep(1);
end;

{//////////////////////////////////////////////////////////////////////////////}
procedure TMsgThread.QuitThread;
begin
{$IFDEF USE_WINDOW_MESSAGE}
PostMessage(FMSGWin,WM_QUIT,0,0);
{$ELSE}
PostThreadMessage(ThreadID,WM_QUIT,0,0);
{$ENDIF}
end;

{------------------------------------------------------------------------------}
procedure TMsgThread.QuitThreadWait;
begin
QuitThread;
WaitTerminate;
end;

{------------------------------------------------------------------------------}
procedure TMsgThread.SetDoLoop(const Value: Boolean);
begin
if Value = fDoLoop then Exit;
fDoLoop := Value;
if fDoLoop then
PostMsg(WM_USER,0,0);
end;

{------------------------------------------------------------------------------}
//Can only call this method in MAIN Thread!!
procedure TMsgThread.WaitTerminate;
var
xStart:Cardinal;
begin
xStart:=GetTickCount;
try
//EnableWindow(Application.Handle,False);
while WaitForSingleObject(Handle, 10) = WAIT_TIMEOUT do
begin
Application.ProcessMessages;
if GetTickCount > (xStart + 4000) then
begin
TerminateThread(Handle, 0);
Beep;
Break;
end;
end;
finally
//EnableWindow(Application.Handle,True);
end;
end;

{------------------------------------------------------------------------------}
procedure TMsgThread.PostMsg(Msg: Cardinal; wParam, lParam: Integer);
begin
{$IFDEF USE_WINDOW_MESSAGE}
postMessage(FMSGWin,Msg,wParam,lParam);
{$ELSE}
EnterCriticalSection(FCtlSect);
try
FEventList.Add(nil);
PostThreadMessage(ThreadID,Msg,wParam,lParam);
finally
LeaveCriticalSection(FCtlSect);
end;
{$ENDIF}
end;

{------------------------------------------------------------------------------}
procedure TMsgThread.SendMsg(Msg: Cardinal; wParam, lParam: Integer);
{$IFNDEF USE_WINDOW_MESSAGE}
var
aEvent:PHandle;
{$ENDIF}
begin
{$IFDEF USE_WINDOW_MESSAGE}
SendMessage(FMSGWin,Msg,wParam,lParam);
{$ELSE}
EnterCriticalSection(FCtlSect);
try
New(aEvent);
aEvent^ := CreateEvent(nil, True, False, nil);
FEventList.Add(aEvent);
PostThreadMessage(ThreadID,Msg,wParam,lParam);
finally
LeaveCriticalSection(FCtlSect);
end;
WaitForSingleObject(aEvent^,INFINITE);
{$ENDIF}
end;

end.

我参考了一下msdn,还有windows核心编程.
写了一个类来封装这个功能,不知道对不对.
里面使用了两个方法,一个使用一个隐含窗体来处理消息
还有一个是直接使用thread的消息队列来处理,但是这个时候sendmessage无法工作,所以我自己设想了一个方法,虽然不完全达到了要求但是我简单测试了一下,好像还能工作.

切换两种工作方式要修改编译条件
{$DEFINE USE_WINDOW_MESSAGE} 使用隐含窗体来处理消息
{-$DEFINE USE_WINDOW_MESSAGE} 使用线程消息队列来处理消息

还有我想要等待线程开始进行消息循环的时候create函数才返回.但是现在好像还没有这样(用一个事件来处理).只是开始进入了threadexecute函数,线程的create就返回了.可能会出问题.

通过设置 DoLoop属性可以设定线程是否循环(不阻塞等待消息),这样派生类线程在循环做一些其他事情的同时还可以接受消息. 例如:派生类里面循环发送缓冲区的数据,还可以响应其他线程发送过来的消息(如停止,启动,退出,等等)

我一般在线程中需要使用消息循环时是直接用
if (PeekMessage(msg,0,0,0,PM_REMOVE)) then
begin
// 这里对特定的已知消息进行处理
end
else
begin
TranslateMessage(Msg);
DispatchMessage(Msg);
end;
这样进行，实践证明是可行的。你的代码好象也是这样进行，而且更详细，我觉得肯定不错。