MFC主线程使用WaitForSingleObject阻塞的问题

在MFC程序的主线程中如果使用WaitForSingleObject等线子线程,而子线程里使用了有关于消息的函数,比如SetWindowText,InsertItem,SetItemText这些函数,就有会导致主主线程阻塞问题,看看这段代码。

DWORD WINAPI ThreadProc(
						LPVOID lpParameter   // thread data
						)
{
	CMFCWaitThreadDlg *pDlg = (CMFCWaitThreadDlg*)lpParameter;

	for (int i=0;i<=10;i++)
	{
		OutputDebugStringA("test");
		Sleep(2000);
		pDlg->SetWindowText(_T("HEHE"));
		
	}
	return true;
}
void CMFCWaitThreadDlg::OnBnClickedOk()
{
	// TODO: 在此添加控件通知处理程序代码
	DWORD dwID;
	HANDLE hThread;
	hThread = CreateThread(0,0,ThreadProc,this,0,&dwID);

	DWORD dwRet = WaitForSingleObject(hThread,INFINITE);
	if (dwRet == WAIT_OBJECT_0)
	{
		MessageBoxA(0,"Thread exit",0,0);
	}

}


主线程出现阻塞问题的原因是,因为SetWindowText调用了SendMessage,借助了消息循环,然后主线程又Waitxxxxx,必然会阻塞,最终导致工作线程Crash掉了。还好微软提供了另一个函数MsgWaitForMultipleObjects,用这个就能搞定了,看看下面这段代码,把WaitForSingleObject那一段给替换了,跑一跑试试,就没问题了。

DWORD WINAPI ThreadProc(
						LPVOID lpParameter   // thread data
						)
{
	CMFCWaitThreadDlg *pDlg = (CMFCWaitThreadDlg*)lpParameter;

	for (int i=0;i<=10;i++)
	{
		OutputDebugStringA("test");
		Sleep(2000);
		pDlg->SetWindowText(_T("HEHE"));
		
	}
	return true;
}
void CMFCWaitThreadDlg::OnBnClickedOk()
{
	// TODO: 在此添加控件通知处理程序代码
	DWORD dwID;
	HANDLE hThread;
	hThread = CreateThread(0,0,ThreadProc,this,0,&dwID);

	while(TRUE)
	{

		DWORD result ; 
		MSG msg ; 

		result = MsgWaitForMultipleObjects(1, &hThread, 
			FALSE, INFINITE, QS_ALLINPUT); 

		if (result == (WAIT_OBJECT_0))
		{
			break;
		} 
		else 
		{ 
			PeekMessage(&msg, NULL, 0, 0, PM_REMOVE);
			DispatchMessage(&msg); 
		} 
	}

	MessageBoxA(0,"Thread exit",0,0);

}


 

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