MFC 全接触 (一)

亦凉 2021-12-20 18:23 206阅读 0赞

以前对于MFC的了解十分肤浅，只知道MFC = Microsoft Foundation Class，后来还道听途说了很多关于她的风流韵事。有人说她如维纳斯一般美丽，也有人说她和犹大一般丑恶。现在为了手头上的事情，我要从新认识这位也许风华不在的女子了，不管她长得如何，我都得去揭开她那对于我来说神秘的面纱。  
还是从打招呼开始吧，以免把她吓着了。于是，我战战兢兢的跟MFC say hello\[1\]了。  
 MyApp.h:

![None.gif][] class  CMyApp :  public  CWinApp  
![ExpandedBlockStart.gif][None.gif]![ContractedBlock.gif][None.gif] ![dot.gif][None.gif] \{  
![InBlock.gif][None.gif]public:  
![InBlock.gif][None.gif]virtual BOOL InitInstance();  
![ExpandedBlockEnd.gif][None.gif]\} ;  
![None.gif][]  
![None.gif][] //  frame window class   
![None.gif][] class  CMyFrame :  public  CFrameWnd  
![ExpandedBlockStart.gif][None.gif]![ContractedBlock.gif][None.gif] ![dot.gif][None.gif] \{  
![InBlock.gif][None.gif]public:  
![InBlock.gif][None.gif] CMyFrame();  
![InBlock.gif][None.gif]protected:  
![InBlock.gif][None.gif]// "afx\_msg" indicates that the function is part  
![InBlock.gif][None.gif]// of the MFC library message dispatch system  
![InBlock.gif][None.gif] afx\_msg void OnPaint();  
![InBlock.gif][None.gif] DECLARE\_MESSAGE\_MAP()  
![ExpandedBlockEnd.gif][None.gif]\} ;

MyApp.cpp:

![None.gif][] \#include  < afxwin.h >  //  MFC library header file declares base classes   
![None.gif][] \#include  " myapp.h "   
![None.gif][]  
![None.gif][]CMyApp theApp;  //  the one and only CMyApp object   
![None.gif][]   
![None.gif][]BOOL CMyApp::InitInstance()  
![ExpandedBlockStart.gif][None.gif]![ContractedBlock.gif][None.gif] ![dot.gif][None.gif] \{  
![InBlock.gif][None.gif] m\_pMainWnd =new CMyFrame();  
![InBlock.gif][None.gif] m\_pMainWnd\->ShowWindow(m\_nCmdShow);  
![InBlock.gif][None.gif]  
![InBlock.gif][None.gif] m\_pMainWnd\->UpdateWindow();  
![InBlock.gif][None.gif]return TRUE;  
![ExpandedBlockEnd.gif][None.gif]\}   
![None.gif][]  
![None.gif][]BEGIN\_MESSAGE\_MAP(CMyFrame, CFrameWnd)  
![None.gif][] ON\_WM\_PAINT()  
![None.gif][]END\_MESSAGE\_MAP()  
![None.gif][]  
![None.gif][]CMyFrame::CMyFrame()  
![ExpandedBlockStart.gif][None.gif]![ContractedBlock.gif][None.gif] ![dot.gif][None.gif] \{  
![InBlock.gif][None.gif] Create(NULL, "MYAPP Application");  
![ExpandedBlockEnd.gif][None.gif]\}   
![None.gif][]  
![None.gif][] void  CMyFrame::OnPaint()  
![ExpandedBlockStart.gif][None.gif]![ContractedBlock.gif][None.gif] ![dot.gif][None.gif] \{  
![InBlock.gif][None.gif] CPaintDC dc(this);  
![InBlock.gif][None.gif] dc.TextOut(0, 0, "Hello, MFC!");  
![ExpandedBlockEnd.gif][None.gif]\}

程序的静态分析：  
由于所有的windows程序都开始于WinMain()函数，而在这段程序中并没有看到这个函数，事实上这个函数被封装到了MFC中了；CMyApp继承于类CWinApp，而CWinApp又继承于CWinThread。因此CWinThread是CMyApp的超类，m\_pMainWnd 是定义在类CWinThread中的访问控制为public的CWnd\*。在头文件及源文件中，宏定义也用到了多次，如afx \_msg，它仅仅是一个占位符，以说明该函数是属于消息处理函数；而DECLARE\_MESSAGE\_MAP()、BEGIN\_MESSAGE\_MAP(CMyFrame, CFrameWnd)和END\_MESSAGE\_MAP()更是暗藏玄机。  
  
程序的动态分析：  
说实在的，这个简单的程序已经运行了很多次了，以前都是一带而过，而现在仔细想想，里面却包含了很多自己完全不知道的东西，那么就干脆来一次最彻底的接触。于是按下了F11的快捷键，进行Step Into Debug。  
首先黄色箭头停在了APPMODUL.cpp文件中，而不是我所预料的那样出现在MyApp.cpp文件：

![None.gif][]extern"C"int  WINAPI  
![None.gif][]\_tWinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance,  
![None.gif][] LPTSTR lpCmdLine, int  nCmdShow)  
![ExpandedBlockStart.gif][None.gif]![ContractedBlock.gif][None.gif]![dot.gif][None.gif] \{  
![InBlock.gif][None.gif]// call shared/exported WinMain  
![InBlock.gif][None.gif]return AfxWinMain(hInstance, hPrevInstance, lpCmdLine, nCmdShow);  
![ExpandedBlockEnd.gif][None.gif]\}

看来程序的入口就在这里了。\_tWinMain的函数体只是简单的调用了AfxWinMain函数。OK，F11 again。  
  
黄色箭头来到了WINMAIN.cpp文件中：

![None.gif][]int  AFXAPI AfxWinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance,  
![None.gif][] LPTSTR lpCmdLine, int  nCmdShow)  
![ExpandedBlockStart.gif][None.gif]![ContractedBlock.gif][None.gif]![dot.gif][None.gif] \{  
![InBlock.gif][None.gif] ASSERT(hPrevInstance == NULL);  
![InBlock.gif][None.gif]  
![InBlock.gif][None.gif]int nReturnCode =\-1;  
![InBlock.gif][None.gif] CWinThread\* pThread = AfxGetThread();  
![InBlock.gif][None.gif] CWinApp\* pApp = AfxGetApp();  
![InBlock.gif][None.gif]  
![InBlock.gif][None.gif]// AFX internal initialization  
![InBlock.gif][None.gif]if (!AfxWinInit(hInstance, hPrevInstance, lpCmdLine, nCmdShow))  
![InBlock.gif][None.gif]goto InitFailure;  
![InBlock.gif][None.gif]  
![InBlock.gif][None.gif]// App global initializations (rare)  
![InBlock.gif][None.gif]if (pApp != NULL &&!pApp\->InitApplication())  
![InBlock.gif][None.gif]goto InitFailure;  
![InBlock.gif][None.gif]  
![InBlock.gif][None.gif]// Perform specific initializations  
![InBlock.gif][None.gif]if (!pThread\->InitInstance())  
![ExpandedSubBlockStart.gif][None.gif]![ContractedSubBlock.gif][None.gif]![dot.gif][None.gif]\{  
![InBlock.gif][None.gif]if (pThread\->m\_pMainWnd != NULL)  
![ExpandedSubBlockStart.gif][None.gif]![ContractedSubBlock.gif][None.gif]![dot.gif][None.gif]\{  
![InBlock.gif][None.gif] TRACE0("Warning: Destroying non-NULL m\_pMainWnd ");  
![InBlock.gif][None.gif] pThread\->m\_pMainWnd\->DestroyWindow();  
![ExpandedSubBlockEnd.gif][None.gif] \}  
![InBlock.gif][None.gif] nReturnCode = pThread\->ExitInstance();  
![InBlock.gif][None.gif]goto InitFailure;  
![ExpandedSubBlockEnd.gif][None.gif] \}  
![InBlock.gif][None.gif] nReturnCode = pThread\->Run();  
![InBlock.gif][None.gif]  
![InBlock.gif][None.gif]InitFailure:  
![InBlock.gif][None.gif]\#ifdef \_DEBUG  
![InBlock.gif][None.gif]// Check for missing AfxLockTempMap calls  
![InBlock.gif][None.gif]if (AfxGetModuleThreadState()\->m\_nTempMapLock !=0)  
![ExpandedSubBlockStart.gif][None.gif]![ContractedSubBlock.gif][None.gif]![dot.gif][None.gif]\{  
![InBlock.gif][None.gif] TRACE1("Warning: Temp map lock count non-zero (%ld). ",  
![InBlock.gif][None.gif] AfxGetModuleThreadState()\->m\_nTempMapLock);  
![ExpandedSubBlockEnd.gif][None.gif] \}  
![InBlock.gif][None.gif] AfxLockTempMaps();  
![InBlock.gif][None.gif] AfxUnlockTempMaps(\-1);  
![InBlock.gif][None.gif]\#endif  
![InBlock.gif][None.gif]  
![InBlock.gif][None.gif] AfxWinTerm();  
![InBlock.gif][None.gif]return nReturnCode;  
![ExpandedBlockEnd.gif][None.gif]\}

在AfxWinMain方法中，  
首先，通过调用AfxGetThread方法获得一个CWinThread的类指针。继续step into 到AfxGetThread方法，可以看到该方法包含了获取当前进程指针的语句，如果得到的进程指针为空的话，则调用AfxGetApp以返回一个CWinThread的类指针。当执行了获取当前进程指针的语句后，可以发现返回的CWinThread类指针对应的类为CMyApp；  
 接着，通过调用AfxGetApp()获得一个CWinApp的类指针。我们可以发现pThread和pApp这两个指针对应着相同的地址，即都是CMyApp类指针对应的类亦为CMyApp；  
在调用了两个MFC本身提供的初始化方法之后，调用了在CMyApp中实现的InitInstance方法；紧跟着就是一个十分重要的方法了—— Run。step into到Run方法，我们可以看到Run方法中包含了一个无限的循环，在这个循环当中，不断的从消息队列中获取消息并分发消息，直到获取的消息为退出(WM\_QUIT)的时候才终止。  
调试花了不少的时间，机子还宕掉了一回，这下总算约莫看见了MFC的背影了，让我们下次再续吧。  
  
Reference: \[1\] 源代码摘自Programming Microsoft Visual C++ (Fifth Edtion)，略有更改。

转载于:https://www.cnblogs.com/perhaps/archive/2004/08/04/29919.html

[None.gif]: