CWinThread消息循环错误 [英] CWinThread message loop error

问题描述

CWinThread 消息循环错误



在我的应用程序中创建一个帖子。

CWinThread message loop error

create a thread in my application.

m_scanThread = (CScanThread*)AfxBeginThread(RUNTIME_CLASS(CScanThread)); 

这个线程调用消息循环但是在循环时冻结。当关闭主线程时

继续循环并给出exception.why？救命？

this thread call message loop but freeze while loop.when close the main thread
continue while loop and give exception.why ? help?

MSG Msg; 
BOOL bRet;           

while (bRet = ::GetMessage((LPMSG)&Msg,NULL, 0, 0) != 0)

推荐答案

你需要显示更多代码......但是在后面，为什么你有一个带有 CWinThread 的消息循环？ CWinThread 是一个类，您可以从...派生自己的线程类，这意味着您没有显式创建自己的循环，这是由框架完成的。



看到这个简单的例子 [ ^ ] ...

You need to show more code... but off the back, why do you have a message loop with a CWinThread? A CWinThread is a class that you can derive your own thread class from... meaning you don't explicitly create your own loop, that's done by the framework.

See this simple example[^]...

因为我在CWinThread类中使用了消息循环来连接twain（扫描程序）并获取扫描程序消息。

because i used message loop in CWinThread class for connect twain (scanner) and get scanner messages.

m_scanThread = (CScanThread*)AfxBeginThread(RUNTIME_CLASS(CScanThread));
//m_scanThread->CreateThread();
m_scanThread->PostThreadMessage(WM_SCAN,(WPARAM)pScannerListCombo->GetItem(sel), (LPARAM)1);

void CScanThread::Scan(WPARAM wParam, LPARAM lParam)
{	
	try
	{ 
		this->connectDSM();
	//fill data source
	this->m_pDataSource = NULL;
	pTW_IDENTITY pID = NULL;
	int   index = 0;
	while( NULL != (pID =  this->getDataSource(index)) )
	{  
		if( (LPWSTR)wParam == CString(pID->ProductName) )
		{
			this->m_pDataSource = pID;
			break;
		}
		index++;
	 } 

		m_bKill = FALSE;	// Indicates that the UI-thread is activated and it is used for displaying the dialog box.
		m_bRunning = TRUE;

		if(this->m_DSMState > 4)
			return; // Already Enabled
		if(this->m_pDataSource != NULL)
			this->loadDS(this->m_pDataSource->Id);

		if(this->enableDS(NULL,false))
		{		
			MSG Msg; 
			BOOL bRet;
		//CMainFrame* pp =	(CMainFrame*)(AfxGetApp()->m_pMainWnd);
		
//freeze this point
			while (bRet = ::GetMessage((LPMSG)&Msg,NULL, 0, 0) != 0)
			{

				TW_EVENT twEvent = {0};
				twEvent.pEvent = (TW_MEMREF)&Msg;
				twEvent.TWMessage = MSG_NULL;
				TW_UINT16  twRC = TWRC_NOTDSEVENT;
				twRC = _DSM_Entry(this->getAppIdentity(),
								  this->m_pDataSource,
							      DG_CONTROL,
							      DAT_EVENT,
							      MSG_PROCESSEVENT,
							     (TW_MEMREF)&twEvent);

			  //TODO:
			  //if(!gUSE_CALLBACKS && twRC==TWRC_DSEVENT)
			  if( twRC==TWRC_DSEVENT)
			  {
				// check for message from Source
				switch (twEvent.TWMessage)
				{
				  case MSG_XFERREADY:
				  case MSG_CLOSEDSREQ:
				  case MSG_NULL:
					this->m_DSMessage = twEvent.TWMessage;
					break;

				  case MSG_CLOSEDSOK:
					TRACE(L"\nError - MSG_CLOSEDSOK in MSG_PROCESSEVENT loop for Scan\n");
					break;

				  default:
					TRACE(L"\nError - Unknown message in MSG_PROCESSEVENT loop for Scan\n");
					break;
				}
			  }
				else
				{
					TranslateMessage ((LPMSG)&Msg);
					DispatchMessage ((LPMSG)&Msg);
				}

			}
  
			//::SendMessage(this->m_hWnd , WM_GETMESSAGE , (WPARAM) m_pDataSource , 0);

		//			// If we are using callbacks, there is nothing to do here except sleep
		//// and wait for our callback from the DS.  If we are not using them, 
		//// then we have to poll the DSM.
		//	MSG Msg;
		//	//while (GetMessage((LPMSG)&Msg, NULL, 0, 0))
	
		//	while (PeekMessage((LPMSG)&Msg, NULL, 0, 0,PM_REMOVE))
		//	{

		//		if (!AfxGetApp ()->PumpMessage ()) { 
		//			 ::PostQuitMessage (0); 
		//			 return; 
		//		} 

		//		TW_EVENT twEvent = {0};
		//		twEvent.pEvent = (TW_MEMREF)&Msg;
		//		twEvent.TWMessage = MSG_NULL;
		//		TW_UINT16  twRC = TWRC_NOTDSEVENT;
		//		twRC = _DSM_Entry( getAppIdentity(),
		//						   m_pDataSource,
		//						   DG_CONTROL,
		//						   DAT_EVENT,
		//						   MSG_PROCESSEVENT,
		//						   (TW_MEMREF)&twEvent);
		//		 if(m_DSMessage == MSG_XFERREADY)
		//		 {
		//			 int i =0;
		//	 
		//		}
		//		else
		//		{
		//			TranslateMessage ((LPMSG)&Msg);
		//			DispatchMessage ((LPMSG)&Msg);
		//		}
		//	}

		//	//// Scan is done, disable the ds, thus moving us back to state 4 where we
		//	//// can negotiate caps again.
		//	//this->disableDS();
		}
	}
    catch(...)
	{

	}
	m_bKill = TRUE;
	m_bRunning = FALSE;
}

可能有以下两种情况之一



1. br />

There is possible one of two situations

1.

while ( ....GetMessage ...) <---- freezing here
{
}

2.

2.

while ( ....GetMessage ...) <---- not freezing here
{
   <---- if there nothing happens, then it is an infinite loop.
   The message have to be dispatched, with DispatchMessage
}

要结束消息循环，你应该调用来自当前线程的PostMessage，或来自其他线程的PostThreadMessage，带有消息WM_QUIT

And to end the message loop you should call PostMessage from current thread, or PostThreadMessage from other thread, with message WM_QUIT

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