让应用程序只运行一个实例的实现方法

BOOL CMutexApp::InitInstance()

{

       //创建命名信标对象。

       HANDLE hSem=CreateSemaphore(NULL,1,1,"维新");

       if(hSem)  //信标对象创建成功。

       {

              //信标对象已经存在，则程序已有一个实例在运行。

              if(ERROR_ALREADY_EXISTS==GetLastError())

              {                 

                     CloseHandle(hSem);      //关闭信号量句柄。

//获取桌面窗口的一个子窗口。

                     HWND hWndPrev=::GetWindow(::GetDesktopWindow(),GW_CHILD);  

                     while(::IsWindow(hWndPrev))

                     {

                     //判断窗口是否有我们预先设置的标记，如有，则是我们寻找的窗口，并将它激活。

                            if(::GetProp(hWndPrev,"维新"))  

                            {

                            //如果主窗口已最小化，则恢复其大小。

                                   if (::IsIconic(hWndPrev))    

                                          ::ShowWindow(hWndPrev,SW_RESTORE);

                                   //将应用程序的主窗口激活。

                                   ::SetForegroundWindow(hWndPrev);

                                   return FALSE;                      //退出实例。

                            }

                            //继续寻找下一个窗口。

                            hWndPrev = ::GetWindow(hWndPrev,GW_HWNDNEXT);

                     }

                     AfxMessageBox("已有一个实例在运行，但找不到它的主窗口！");

              }

       }

       else

       {

              AfxMessageBox("创建信标对象失败，程序退出！");

              return FALSE;

       }

       AfxEnableControlContainer();

       // Standard initialization

       // If you are not using these features and wish to reduce the size

       //  of your final executable, you should remove from the following

       //  the specific initialization routines you do not need.

#ifdef _AFXDLL

       Enable3dControls();                     // Call this when using MFC in a shared DLL

#else

       Enable3dControlsStatic();      // Call this when linking to MFC statically

#endif

       // Change the registry key under which our settings are stored.

       // TODO: You should modify this string to be something appropriate

       // such as the name of your company or organization.

       SetRegistryKey(_T("Local AppWizard-Generated Applications"));

       LoadStdProfileSettings();  // Load standard INI file options (including MRU)

       // Register the application's document templates.  Document templates

       //  serve as the connection between documents, frame windows and views.

       CSingleDocTemplate* pDocTemplate;

       pDocTemplate = new CSingleDocTemplate(

              IDR_MAINFRAME,

              RUNTIME_CLASS(CMutexDoc),

              RUNTIME_CLASS(CMainFrame),       // main SDI frame window

              RUNTIME_CLASS(CMutexView));

       AddDocTemplate(pDocTemplate);

       // Parse command line for standard shell commands, DDE, file open

       CCommandLineInfo cmdInfo;

       ParseCommandLine(cmdInfo);

       // Dispatch commands specified on the command line

       if (!ProcessShellCommand(cmdInfo))

              return FALSE;

       // The one and only window has been initialized, so show and update it.

       m_pMainWnd->ShowWindow(SW_SHOW);

       m_pMainWnd->UpdateWindow();

       return TRUE;

}

2、在框架类的OnCreate()函数中设置查找标记。

int CMainFrame::OnCreate(LPCREATESTRUCT lpCreateStruct)

{

       if (CFrameWnd::OnCreate(lpCreateStruct) == -1)

              return -1;

       if (!m_wndToolBar.CreateEx(this, TBSTYLE_FLAT, WS_CHILD | WS_VISIBLE | CBRS_TOP

              | CBRS_GRIPPER | CBRS_TOOLTIPS | CBRS_FLYBY | CBRS_SIZE_DYNAMIC) ||

              !m_wndToolBar.LoadToolBar(IDR_MAINFRAME))

       {

              TRACE0("Failed to create toolbar/n");

              return -1;      // fail to create

       }

       if (!m_wndStatusBar.Create(this) ||

              !m_wndStatusBar.SetIndicators(indicators,

                sizeof(indicators)/sizeof(UINT)))

       {

              TRACE0("Failed to create status bar/n");

              return -1;      // fail to create

       }

       // TODO: Delete these three lines if you don't want the toolbar to

       //  be dockable

       m_wndToolBar.EnableDocking(CBRS_ALIGN_ANY);

       EnableDocking(CBRS_ALIGN_ANY);

       DockControlBar(&m_wndToolBar);

       //设置查找标记。

       ::SetProp(m_hWnd,"维新",(HANDLE)1);

       return 0;

}

3、在程序退出是删除设置的标记，在框架类中响应WM_DESTROY消息，进行处理。

void CMainFrame::OnDestroy()

{

       CFrameWnd::OnDestroy();

       // TODO: Add your message handler code here

       //删除所设置的标记。

       ::RemoveProp(m_hWnd,"维新");

}

至此，使应用程序只运行一个实例的功能就完成了。