单一实例

对话框项目

// APP 里面添加互斥量
class CvideoHelperApp : public CWinApp
{
...
private:
	HANDLE m_hMutex;
    ...
}

BOOL CvideoHelperApp::InitInstance()
{
    m_hMutex = CreateMutex(NULL, TRUE, _T("注册信息"));
	if (NULL == m_hMutex)
	{
		return FALSE;
	}
	if (GetLastError() == ERROR_ALREADY_EXISTS)
	{
		HWND hProgramWnd = ::FindWindow(NULL, _T("注册信息"));
		if (hProgramWnd)
		{
			WINDOWPLACEMENT* pWndpl = NULL;
			WINDOWPLACEMENT wpm;
			pWndpl = &wpm;
			GetWindowPlacement(hProgramWnd, &wpm);
			if (pWndpl)
			{
				//将运行的程序窗口还原成正常状态
				pWndpl->showCmd = SW_SHOWNORMAL;
				::SetWindowPlacement(hProgramWnd, pWndpl);
				SetWindowPos(hProgramWnd, HWND_TOPMOST, 0, 0, 0, 0, SWP_NOSIZE | SWP_NOMOVE);
			}
		}
		CloseHandle(m_hMutex);
		m_hMutex = NULL;
		return FALSE;
	}
    ...
}

// 释放资源
int CvideoHelperApp::ExitInstance()
{
	if (NULL != m_hMutex)
		CloseHandle(m_hMutex);
	m_hMutex = NULL;

	return CWinApp::ExitInstance();
}

多文档项目

BOOL CMainFrame::PreCreateWindow(CREATESTRUCT& cs)
{
	if( !CMDIFrameWnd::PreCreateWindow(cs) )
		return FALSE;
	// TODO: Modify the Window class or styles here by modifying
	//  the CREATESTRUCT cs

	cs.style |= WS_SYSMENU |WS_MINIMIZEBOX|WS_MAXIMIZEBOX;//  | WS_VISIBLE | FWS_ADDTOTITLE | | WS_MINIMIZEBOX| WS_OVERLAPPED | WS_CAPTION | WS_SYSMENU | WS_MAXIMIZEBOX | WS_MAXIMIZE;


	//   change   mainframe's   class   name,   so   I   can   easily   find   it   further.   
	LPTSTR APP_CLASSNAME = TEXT("ASLucky_SCHelper");
	WNDCLASS   wndCls;   
	HINSTANCE   hInst = AfxGetInstanceHandle();   

	if(!(::GetClassInfo(hInst,APP_CLASSNAME,&wndCls)))   
	{   
		if(::GetClassInfo(hInst,cs.lpszClass,&wndCls))   
		{   
			wndCls.lpszClassName = APP_CLASSNAME;   
			wndCls.hIcon = AfxGetApp()->LoadIcon(IDR_MAINFRAME);   
			if   (!AfxRegisterClass(&wndCls))   
				AfxThrowResourceException();   
		}else   
			AfxThrowResourceException();   
	}   
	cs.lpszClass = APP_CLASSNAME;


	return TRUE;
}


bool FirstInstance(TCHAR* pstrClass)
{
	//CWnd* pwndFirst = CWnd::FindWindow((LPCTSTR)(DWORD_PTR)WC_DIALOG,strCaption);//for dialog
	CWnd* pwndFirst = CWnd::FindWindow(pstrClass, NULL);
	if (!pwndFirst)
	{
		return true;
	}
	// another instance is already running - activate it
	CWnd* pwndPopup = pwndFirst->GetLastActivePopup();
	pwndFirst->SetForegroundWindow();
	if (pwndFirst->IsIconic())
		pwndFirst->ShowWindow(SW_SHOWNORMAL);
	if (pwndFirst != pwndPopup)
		pwndPopup->SetForegroundWindow();
	return false;
}

BOOL CEasyReminderApp::InitInstance()
{
	if ( !FirstInstance(TEXT("ASLucky_EasyReminder")) )
	{
		return FALSE;
	}
。。。
}