在两个不同的程序实例中发送消息,相互通信
有时候,我们需要让不同的应用程序实例间相互发送消息,比如,为了确保对于同一个应用程序,只运行一个的实例,在启动程序时,先检测是否已有此程序的实例运行,如果有,则给此实例发送消息,通知它激活并保持最前,已提醒用户此程序已经在运行。
利用Win32 API RegisterWindowMessage()可以实现这一功能。
1.要点
- 用Win32 API RegisterWindowMessage()注册生成一个消息,此消息在整个Session中保持唯一,因此可用于同一个Session中不同的应用程序实例相互通信;
- 用PostMessage或SendMessage广播此消息;
- 需要接收处理此消息的程序实例,使用ON_REGISTERED_MESSAGE()宏接收处理此广播消息;
2.实现代码
1: //Define a unique const string to create the broadcast message
2: //We can use the GuidGen tool to make sure this string is a unique one
3: const static LPCTSTR g_AciveMsgName = _T("DBCAAC01-2744-43EE-9FFC-7CD41C672842");4:5: //Generate a broadcast message
6: UINT broadcastMsg = ::RegisterWindowMessage(g_AciveMsgName);7:8: //Broadcast message
9: ::PostMessage(HWND_BROADCAST,broadcastMsg,0,0);10:11: //Receive and process this message,if the receiver is a different app instance,it need
12: //also to call the ::RegisterWindowMessage(g_AciveMsgName) API to get the message code
13: //NOTE:This message code is assotiated with the global unique string(g_AciveMsgName)
14: //and it's allocated by the windows system
15: BEGIN_MESSAGE_MAP(...)16: //......
17: ON_REGISTERED_MESSAGE(s_WM_ACTIVEWND,OnActiveWnd)18: //......
19: END_MESSAGE_MAP()20:21: void CDlg::OnActiveWnd()
22: {23: // Do something to response this broadcasted message
24: //......
25: }