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。
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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。
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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); } |