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MFC框架梳理

2018年01月11日 ⁄ 综合 ⁄ 共 7789字 ⁄ 字号 评论关闭

APPMODUL.cpp中的WinMain函数:

// This is a part of the Microsoft Foundation Classes C++ library.
// Copyright (C) 1992-1998 Microsoft Corporation
// All rights reserved.
//
// This source code is only intended as a supplement to the
// Microsoft Foundation Classes Reference and related
// electronic documentation provided with the library.
// See these sources for detailed information regarding the
// Microsoft Foundation Classes product.

#include "stdafx.h"

#ifdef _DEBUG
#undef THIS_FILE
static char THIS_FILE[] = __FILE__;
#endif

/////////////////////////////////////////////////////////////////////////////
// export WinMain to force linkage to this module

extern int AFXAPI AfxWinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance,
	LPTSTR lpCmdLine, int nCmdShow);

extern "C" int WINAPI
_tWinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance,
	LPTSTR lpCmdLine, int nCmdShow)
{
	// call shared/exported WinMain
	return AfxWinMain(hInstance, hPrevInstance, lpCmdLine, nCmdShow);
}

/////////////////////////////////////////////////////////////////////////////
// initialize app state such that it points to this module's core state

BOOL AFXAPI AfxInitialize(BOOL bDLL, DWORD dwVersion)
{
	AFX_MODULE_STATE* pModuleState = AfxGetModuleState();
	pModuleState->m_bDLL = (BYTE)bDLL;
	ASSERT(dwVersion <= _MFC_VER);
	UNUSED(dwVersion);  // not used in release build
#ifdef _AFXDLL
	pModuleState->m_dwVersion = dwVersion;
#endif
#ifdef _MBCS
	// set correct multi-byte code-page for Win32 apps
	if (!bDLL)
		_setmbcp(_MB_CP_ANSI);
#endif //_MBCS
	return TRUE;
}

// force initialization early
#pragma warning(disable: 4074)
#pragma init_seg(lib)

#ifndef _AFXDLL
void AFX_CDECL _AfxTermAppState()
{
	// terminate local data and critical sections
	AfxTermLocalData(NULL, TRUE);
	AfxCriticalTerm();

	// release the reference to thread local storage data
	AfxTlsRelease();
}
#endif

#ifndef _AFXDLL
char _afxInitAppState = (char)(AfxInitialize(FALSE, _MFC_VER), atexit(&_AfxTermAppState));
#else
char _afxInitAppState = (char)(AfxInitialize(FALSE, _MFC_VER));
#endif

/////////////////////////////////////////////////////////////////////////////

#define _tWinMain   WinMain  _tWinMain 实际上是一个宏,展开之后就是WinMain函数。

找到了WinMain函数,那么它是如何与MFC程序中的各个类组织在一起的呢?

全局变量-》testApp构造函数-》WinMain函数

无论全局变量还是全局对象,程序在运行时,在加载main函数之前,就已经为全局变量或全局对象分配了内存空间。对一个全局对象来说,此时就会调用该对象的构造函数,构造该对象,并进行初始化操作。

每一个MFC程序有且有一个从应用程序类(CWinAPP)派生的类。每一个MFC程序实例有且有一个派生类的实例化对象,也就是theApp全局对象。该对象就表示了应用程序本身。

CTestApp theApp;当一个子类在构造之前会先调用其父类的构造函数。因此theApp对象构造函数CTestApp在调用之前,会调用其父类CWinApp的构造函数,从而就把我们程序自己创建的类与Microsoft提供的基类联起来了。

关于CWinApp的构造函数如下:

CWinApp::CWinApp(LPCTSTR lpszAppName)
{
	if (lpszAppName != NULL)
		m_pszAppName = _tcsdup(lpszAppName);
	else
		m_pszAppName = NULL;

	// initialize CWinThread state
	AFX_MODULE_STATE* pModuleState = _AFX_CMDTARGET_GETSTATE();
	AFX_MODULE_THREAD_STATE* pThreadState = pModuleState->m_thread;
	ASSERT(AfxGetThread() == NULL);
	pThreadState->m_pCurrentWinThread = this;
	ASSERT(AfxGetThread() == this);
	m_hThread = ::GetCurrentThread();
	m_nThreadID = ::GetCurrentThreadId();

	// initialize CWinApp state
	ASSERT(afxCurrentWinApp == NULL); // only one CWinApp object please
	pModuleState->m_pCurrentWinApp = this;
	ASSERT(AfxGetApp() == this);

	// in non-running state until WinMain
	m_hInstance = NULL;
	m_pszHelpFilePath = NULL;
	m_pszProfileName = NULL;
	m_pszRegistryKey = NULL;
	m_pszExeName = NULL;
	m_pRecentFileList = NULL;
	m_pDocManager = NULL;
	m_atomApp = m_atomSystemTopic = NULL;
	m_lpCmdLine = NULL;
	m_pCmdInfo = NULL;

	// initialize wait cursor state
	m_nWaitCursorCount = 0;
	m_hcurWaitCursorRestore = NULL;

	// initialize current printer state
	m_hDevMode = NULL;
	m_hDevNames = NULL;
	m_nNumPreviewPages = 0;     // not specified (defaults to 1)

	// initialize DAO state
	m_lpfnDaoTerm = NULL;   // will be set if AfxDaoInit called

	// other initialization
	m_bHelpMode = FALSE;
	m_nSafetyPoolSize = 512;        // default size
}

pThreadState->m_pCurrentWinThread = this;
根据C++继承性原理,这个this对象代表的是子类CTestapp的对象,即theapp.同时,可以发现CWinApp的构造函数有个LPCTSTR类型的形参:lpszAppName.但是我们程序中CTestApp的构造函数式没有参数的。在第二章介绍C++编程知识时,曾经介绍,如果基类的构造函数带有一个形参,那么子类构造函数需要显示地调用基类带参数的构造。

如果基类的构造函数带有一个形参,那么子类构造函数需要显式地调用基类带参数的构造函数。那么,为什么我们程序中的CTestApp构造函数没有这么做呢?

我们知道,如果某个函数的参数有默认值,那么在调用该函数时可以传递该参数的值,也可以不传递,直接使用默认即可。CWinApp类的定义:

class CWinApp : public CWinThread
{
	DECLARE_DYNAMIC(CWinApp)
public:

// Constructor
	CWinApp(LPCTSTR lpszAppName = NULL);     // app name defaults to EXE name
............................

CWinApp构造函数的形参确实有一个默认值(NULL)。这样,在调用CWinApp类的构造函数时,就不用显示的去传递这个参数的值。

_tWinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance,
	LPTSTR lpCmdLine, int nCmdShow)
{
	// call shared/exported WinMain
	return AfxWinMain(hInstance, hPrevInstance, lpCmdLine, nCmdShow);
}

可以发现,WinMain函数时间上是通过AfxWinMain函数来完成它的功能的。

int AFXAPI AfxWinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance,
	LPTSTR lpCmdLine, int nCmdShow)
{
	ASSERT(hPrevInstance == NULL);

	int nReturnCode = -1;
	CWinThread* pThread = AfxGetThread();
	CWinApp* pApp = AfxGetApp();

	// AFX internal initialization
	if (!AfxWinInit(hInstance, hPrevInstance, lpCmdLine, nCmdShow))
		goto InitFailure;

	// App global initializations (rare)
	if (pApp != NULL && !pApp->InitApplication())
		goto InitFailure;

	// Perform specific initializations
	if (!pThread->InitInstance())
	{
		if (pThread->m_pMainWnd != NULL)
		{
			TRACE0("Warning: Destroying non-NULL m_pMainWnd\n");
			pThread->m_pMainWnd->DestroyWindow();
		}
		nReturnCode = pThread->ExitInstance();
		goto InitFailure;
	}
	nReturnCode = pThread->Run();

InitFailure:
#ifdef _DEBUG
	// Check for missing AfxLockTempMap calls
	if (AfxGetModuleThreadState()->m_nTempMapLock != 0)
	{
		TRACE1("Warning: Temp map lock count non-zero (%ld).\n",
			AfxGetModuleThreadState()->m_nTempMapLock);
	}
	AfxLockTempMaps();
	AfxUnlockTempMaps(-1);
#endif

	AfxWinTerm();
	return nReturnCode;
}

/////////////////////////////////////////////////////////////////////////////

CWinThread* pThread = AfxGetThread();

CWinApp* pApp = AfxGetApp();

AfxWinMain首先调用AfxGetThread函数获得一个CWinTHread类型的指针,接着调用AfxGetApp函数获得一个CWinApp类型的指针。

对test程序来说,pThread和pApp所指向的都是CTestApp类的对象,即theApp全局对象。

接下来调用三个函数完成Win32程序所需要的几个步骤:设计窗口类、注册窗口类、创建窗口、显示窗口、更新窗口、消息循环、以及窗口过程函数

InitApplication函数 该函数完成MFC内部管理方面的工作。接着,调用pThread的InitInstance函数。在Test程序中,可以发现从CWinApp派生的应用程序类CTestApp也有一个InitInstance函数,其声明代码如下所示:

	virtual BOOL InitInstance();

该函数为虚函数,根据类的多态性原理,可以知道AfxWinMain函数这里实际上调用的是子类CTestApp的InitInstace函数

BOOL CTestApp::InitInstance()
{
	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(CTestDoc),
		RUNTIME_CLASS(CMainFrame),       // main SDI frame window
		RUNTIME_CLASS(CTestView));
	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;
}

我们创建的mfc应用程序Test,实际上有两个窗口。其中一个是CMainFrame类对象所代表的应用程序框架窗口。该类有一个PreCreateWindow函数,这是在窗口产生之前被调用的。该函数默认实现代码如下:

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

	return TRUE;
}
BOOL CFrameWnd::PreCreateWindow(CREATESTRUCT& cs)
{
	if (cs.lpszClass == NULL)
	{
		VERIFY(AfxDeferRegisterClass(AFX_WNDFRAMEORVIEW_REG));
		cs.lpszClass = _afxWndFrameOrView;  // COLOR_WINDOW background
	}

	if ((cs.style & FWS_ADDTOTITLE) && afxData.bWin4)
		cs.style |= FWS_PREFIXTITLE;

	if (afxData.bWin4)
		cs.dwExStyle |= WS_EX_CLIENTEDGE;

	return TRUE;
}

在initinstance中:

	m_pMainWnd->ShowWindow(SW_SHOW);
	m_pMainWnd->UpdateWindow();

显示应用程序框架窗口和更新这个窗口。

消息循环:

在AfxWinMain函数实现代码:

nReturnCode = pThread->Run();

窗口类 窗口对象 窗口 的关系!

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