MFC程序的初始化过程

 

 MFC程序是一个Windows程序，它的内部也有窗口注册操作，窗口产生操作，消息循环操作和窗口函数。

 MFC中CwinApp类的两个虚函数InitApplication和InitInstance，前者负责“每一个程序只做一次”的操作，后者负责“每一个例程都得做一次”的操作。通常，系统会（并且有能力）为我们注册一些标准的窗口类（当然也准备了一些标准的窗口函数）。程序设计者在自己的CmyWinApp中改写InitInstance,并在其中把窗口产生出来—这样才有机会在标准的窗口类中指定自己的窗口标题和菜单。下面即使我们新的main函数：

//MY.CPP

CmyWinApp the App;

Void main()

{

    CwinApp *pApp = AfxGetApp(); // pApp指向theApp全局对象

    pApp->InitApplication(); //调用CwinApp::InitApplication

    pApp->InitInstance(); //调用CmyWinApp::InitInstance(因为CmyWinApp改写了它)

    pApp->Run(); //调用CwinApp::Run

}

请注意CMyWinAPP::InitInstance()的操作，以及它所引发的行为：

BOOL CMyWinAPP::InitInstance()

{

    cout<<”CmyWinApp::InitInstance/n”;

    m_pMainWnd = new CmyFrameWnd;//引发CmyFrameWnd:: CmyFrameWnd构造函数

    return TRUE;

}

CmyFrameWnd:: CmyFrameWnd（）

{

    Create();//Create()是虚函数，但CmyFrameWnd未改写它，

//所以引发父类的CmyFrameWnd::Create

}

BOOL CmyFrameWnd::Create()

{

    cout<<”CframeWnd::Create/n”;

    CreateEx();//CreateEx不是虚函数，它继承自CWnd,

//而CframeWnd之中又没有重新定义，故调用CWnd::CreateEx

return TRUE;

}

BOOL CWnd::CrateEx()

{

    cout<<”CWnd::CreateEx/n”;

    PreCteateWindow();//这是个虚函数，CWnd中有定义,CframeWnd也改写了它

Return TRUE;

}

BOOL CframeWnd::PreCreateWindow()

{

    cout<<”CframeWnd::PreCreateWindow/n”;

    return TRUE;

}

 

范例程序

MFC.H

#define BOOL int

#define TRUE 1

#define FALSE 0

#include <iostream.h>

class CObject

{

 public:

    CObject::CObject() { }

    CObject::~CObject() { }

};

class CcmdTarget : public CObject

{

 public:

    CCmdTarget:: CCmdTarget () { }

    CCmdTarget::~CCmdTarget () { }

};

class CwinThread : public CCmdTarget

{

 public:

    CwinThread:: CwinThread () { }

    CwinThread::~ CwinThread () { }

    Virtual BOOL InitInstance(){

Cout<<”CwinThread::InitInstance/n”;

Return TRUE;

}

virtual int Run(){

cout<<”CwinThread::Run/n”;

return 1;

}

};

class CWnd;

class CWinApp : public CwinThread

{

 public:

    CWinApp * m_pCurrentWinApp;

    CWnd * m_pMainWnd;

 Public:

    CWinApp::CWinApp() { pCurrentWinApp = this ;}

    CWinApp::~CWinApp() { }

    virtual BOOl InitApplication () {

        Cout<<”CWinApp::InitApplication/n”;

        Return TRUE;

    }

virtual BOOL InitInstance () {

    cout<<”CWinApp::InitInstance()/n”;

    return TRUE;

}

virtual int Run () {

    cout<<”CWinApp::Run()/n”;

    return CWinThread::Run();

}

};

Class CDocument : public CCmdTarget

{

 public:

    Cdocument:: Cdocument() { }

    Cdocument::~ Cdocument() { }

};

Class CWnd : public CCmdTarget

{

 public:

    CWnd:: CWnd () { }

    CWnd::~CWnd () { }

};

Class CFrameWnd : public CWnd

{

 public:

    CFrameWnd:: CFrameWnd () { }

    CFrameWnd::~CFrameWnd () { }

    BOOL Create ();

    Virtual BOOL PreCreateWindow();

};

Class CView : public CWnd

{

 public:

    CView:: CView () { }

    CView::~ CView () { }

};

//global function

CWinApp *AfxGetApp();

 

 

MFC.CPP

#include “my.h” //本该包含mfc.h，但为了CmyWinapp的定义

extern CmyWinApp theApp ; //external global object

BOOL CWnd::Create()

{

    cout<<”CWnd::Create/n”;

    return TRUE;

}

BOOL CWnd::CreateEx()

{

cout<<”CWnd::CreateEx/n”;

    PreCreateWindow();

return TRUE;

}

BOOL CWnd::PreCreateWindow()

{

    cout<<”CWnd::PreCreateWindow /n”;

    return TRUE;

}

BOOL CframeWnd::Create()

{

    cout<<”CframeWnd::Create/n”;

    CreateEx();

return TRUE;

}

BOOL CframeWnd::PreCreateWindow()

{

    cout<<”CframeWnd::PreCrateWindow/n”;

    return TRUE;

}

CWinApp * AfxApp()

{

 return theApp.m_pCurrentWinApp;

}

 

MY.H

#include <iostream.h>

#include “mfc.h”

class CmyWinApp : public CWinApp

{

 public:

    CmyWinApp:: CmyWinApp() { }

    CmyWinApp::~ CmyWinApp() { }

    virtual BOOL InitInstance();

};

class CmyFrameWnd : public CframeWnd

{

 public:

    CmyFrameWnd();

    ~CmyFrameWnd() {}

};

 

 

MFC.CPP

#include “my.h”

CmyWinApp theApp; //global object

BOOL CMyWinAPP::InitInstance()

{

    cout<<”CmyWinApp::InitInstance/n”;

    m_pMainWnd = new CmyFrameWnd;

    return TRUE;

}

CmyFrameWnd::CmyFrameWnd()

{

    cout<<”CmyFrameWnd::CmyFrame/n”;

    Create();

}

//main()

void main()

{

    CwinApp *pApp = AfxGetApp();

    pApp->InitApplication();

    pApp->InitInstance();

    pApp->Run();

}

程序的输出结果是：

CWinApp::InitApplication

CmyWinApp::InitInstance

CmyFrameWnd:: CmyFrameWnd

CframeWnd::Create

CWnd::CreateEx

CframeWnd::PreCreateWindow

CwinApp::Run

CwinThread::Run