再问一个线程消息的问题，下面是代码，不能运行 ( 积分: 0 )

  • 主题发起人 主题发起人 dalmatians
  • 开始时间 开始时间
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dalmatians

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主窗口：
for i:=0 to 10do
begin
PostThreadMessage(threadId, UM_A, 1, 1);
sleep(50);
end;

线程：
procedure TThread1.execute;
var
msg: TagMsg;
begin
while(true)do begin
getMessage(msg, threadId, 0, WM_USER + 1000);
if(msg.message = UM_A)then
inc(counter);
end;
end;

主窗口向线程发送消息，可是线程就是得不到，为什么，inc(counter)即使不执行
 
试试PeekMessage(Msg, 0, 0, 0, PM_REMOVE)
 
多线程里面用消息，需要模拟一个窗口的，因为消息是windows的特点，只有窗口才可以接收到消息，所以你需要模拟一个看不到的窗口来处理。我有代码，给你贴一个过来吧。也是收藏的别人的代码了。
 
下面一段就是，完整的，可以用的了。感谢写这个代码的人。
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;
proceduredo
HandleException;virtual;
//Inherited the Method to process your own Message
proceduredo
ProcessMsg(var Msg:TMessage);virtual;
//ifdo
Loop = true then
loop this procedure
//Your can use the method todo
some work needed loop.
proceduredo
MsgLoop;virtual;
//Initialize Thread before begin
message loop
proceduredo
Init;virtual;
proceduredo
UnInit;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,do
n'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
propertydo
Loop: 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
{$ENDIF}
//notify Conctructor can returen.
SetEvent(FWaitHandle);
CloseHandle(FWaitHandle);
mRet := True;
try
do
Init;
while mRetdo
//Message Loop
begin
if fDoLoop then
begin
aRet := PeekMessage(Msg,0,0,0,PM_REMOVE);
if aRet and (Msg.message <> WM_QUIT) then
begin
{$IFDEF USE_WINDOW_MESSAGE}
TranslateMessage(Msg);
DispatchMessage(Msg);
{$else
}
uMsg.Msg := Msg.message;
uMsg.wParam := Msg.wParam;
uMsg.lParam := Msg.lParam;
do
ProcessMsg(uMsg);
{$ENDIF}
if Msg.message = WM_QUIT then
mRet := False;
end;
{$IFNDEF USE_WINDOW_MESSAGE}
ClearSendMsgEvent;
//Clear SendMessage Event
{$ENDIF}
do
MsgLoop;
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;
do
ProcessMsg(uMsg);
ClearSendMsgEvent;
//Clear SendMessage Event
{$ENDIF}
end;
end;
end;
do
UnInit;
{$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;

{//////////////////////////////////////////////////////////////////////////////}
{$IFDEF USE_WINDOW_MESSAGE}
procedure TMsgThread.MSGWinProc(var Message: TMessage);
begin
do
ProcessMsg(Message);
with Messagedo
Result:=DefWindowProc(FMSGWin,Msg,wParam,lParam);
end;
{$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;
do
ProcessMsg(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_TIMEOUTdo
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do
Loop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。
 
为什么要发消息？又不是唯一的方法
 
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