深入淺出MFC學習筆記（第三章：MFC六大關鍵技術之仿真：消息映射）

消息映射機制

SDK編程中，一般處理消息的方法就是使用switch/case判斷消息的類型，然後進行響應。更模塊化的方法是使用第一章介紹的消息映射表的方法，把消息和消息處理函數關聯起來。

應該爲每個需要處理消息的類構建一個消息映射表，並將基類與派生類的消息映射表連接起來。當窗口函數比較消息時，就沿着這條繼承路線傳遞下去。 爲了實現這個目的我們仍然使用兩個宏，完成這個功能複雜的構建。

首先定義一個數據結構：

//消息映射表元素類型。

struct AFX_MSGMAP_ENTRY

{

UINT nMessage;

UINT nCode;

UINT nID;

UINT nLastID;

UINT nSig;

AFX_PMSG pfn;

};

struct AFX_MSGMAP

{

AFX_MSGMAP *pBaseMessageMap;//指向基類的本結構。

AFX_MSGMAP_ENTRY*lpEntries;//本類的消息映射表。

};

在定義一個宏：

define DECLARE_MESSAGE_MAP\

static AFX_MSGMAP_ENTRY _messageEntries[];\

static AFX_MSGMAP messageMap;\

virtual AFX_MSGMAP*GetMessageMap()const;

該宏相當於在類中聲明兩個static數據成員和一個虛成員函數。 

它們的定義由以下三個宏實現：

#define BEGIN_MESSAGE_MAP(class_name,base_class)\

AFX_MSGMAP*class_name::GetMessageMap()const\

    {return &class_name::message;}\

AFX_MSGMAP messageMap=\

    {&base_class::messageMap,class_name::_messageEntries}\

AFX_MSGMAP_ENTRY _messageEntries[]=\

    {

#define ON_COMMAND(id,memFunc)\

          WM_COMMAND,0,id,id,AFx_sig_vv\

                           ,(AFX_PMSG)memFunc },\

#define END_MESSAGE_MAP()\

   {0,0,0,0,AfxSig_end,(AFX_PMSG)0}\

以CView爲例，下面的代碼：

class CWnd :public CWnd

{

  public:

    DECLARE_MESSAGE_MAP()

};

BEGIN_MESSAGE_MAP(CView,CWnd)

ON_COMMAND(CViewid,0)

END_MESSAGE_MAP()

展開後變爲：

class CView :public CWnd

{

public:

static AFX_MESSAGE_ENTRY _messageEntries[];

static AFX_MSGMAP messageMap;

virtual AFX_MSGMAP*GetMessageMap()const;

};

AFX_MSGMAP*CView::GetMessageMap()const 

{

return &CView::messagemMap;

}

AFX_MSGMAP CView::messageMap=

{

&(CWnd::messageMap),

(AFX_MSGMAP_ENTRY*)&(CView::_messageEntries)

};

AFX_MSGMAP_ENTRY CView::_messageEntries[]=

{

{WM_COMMAND,0,122,122,1,(AFX_PMSG)0},

{0,0,0,0,0,(AFX_PMSG)0}

}

爲了驗證整個消息映射表，我們在每個類的消息映射表中添加了一個空的消息，這是爲了做點標記，用於標示消息映射表的最後一個消息。MFC當然不是這樣實現的。

/* CCmdTarget是消息傳遞的終點，因此在實現時需要特殊處理，這一點容易出錯，要特別注意。

class CCmdTarget:public CObject

{

DECLARE_DYNCREATE(CCmdTarget)

DECLARE_MESSAGE_MAP()

public:

CCmdTarget()

{

//cout<<"CCmdTarget constructor!"<<endl;

//CreateObject();

}

~CCmdTarget()

{

//cout<<"CCmdTarget destructor!"<<endl;

}

public:

};

IMPLEMENT_DYNCREATE(CCmdTarget,CObject)

 

AFX_MSGMAP CCmdTarget::messageMap=

    {NULL,CCmdTarget::_messageEntries};

AFX_MSGMAP_ENTRY CCmdTarget::_messageEntries[]=

{

   {0,0,10,0,AfxSig_end,0},

   {0,0,0,0,AfxSig_end,0}

};

AFX_MSGMAP*CCmdTarget::GetMessageMap()const

{

    return &CCmdTarget::messageMap;

}

    以下爲包含動態創建、類型識別、消息映射的完整代碼：

#include<iostream>
#include<windows.h>
#include<string>
using namespace std;
class CCmdTarget;
typedef void (CCmdTarget::*AFX_PMSG)(void);

//消息映射表元素類型。
enum AfxSig
{
    AfxSig_end=0,
    AfxSig_vv,
};
struct AFX_MSGMAP_ENTRY
{
    UINT nMessage;
    UINT nCode;
    UINT nID;
    UINT nLastID;
    UINT nSig;
    AFX_PMSG pfn;
};
struct AFX_MSGMAP
{
    AFX_MSGMAP *pBaseMessageMap;//指向基類的本結構。
    AFX_MSGMAP_ENTRY*lpEntries;//本類的消息映射表。
};


#define DECLARE_MESSAGE_MAP()\
  public:\
    static AFX_MSGMAP_ENTRY _messageEntries[];\
    static AFX_MSGMAP messageMap;\
    virtual AFX_MSGMAP*GetMessageMap()const;\

#define BEGIN_MESSAGE_MAP(class_name,base_class)\
    AFX_MSGMAP*class_name::GetMessageMap()const\
       {return &class_name::messageMap;}\
    AFX_MSGMAP class_name::messageMap={&base_class::messageMap,class_name::_messageEntries};\
    AFX_MSGMAP_ENTRY class_name::_messageEntries[]=\
      {

#define ON_COMMAND(id,memFunc)\
      {WM_COMMAND,0,id,id,AfxSig_vv,(AFX_PMSG)memFunc },\

#define END_MESSAGE_MAP()\
       {0,0,0,0,AfxSig_end,(AFX_PMSG)0}\
        };




class CObject;
class CRuntimeClass
{
public:
    char* m_lpszClassName;//對象所屬類名
    int m_nObjectSize;//對象大小
    int m_wSchema;//模式號
    CObject*(PASCAL*m_pfnCreateObject)();//構建函數,抽象類爲NULL
    CRuntimeClass *m_pBaseClasss;//基類CRuntimeClass對象指針。
    static CRuntimeClass *pFirstClass;//鏈表頭指針。static
    CRuntimeClass  *m_pNextClass;//下一指針。
public:
    CObject*CreateObject()
    {
        if(m_pfnCreateObject==NULL)
        {
            cout<<"該類型不支持動態創建！！"<<endl;
            return NULL;
        }
        CObject*pClass=(*m_pfnCreateObject)();
        return pClass;
    }
    static CRuntimeClass*Load()
    {
        cout<<"請輸入要動態創建的類名：";
        string s;
        cin>>s;
        for(CRuntimeClass*pClass=pFirstClass;pClass;pClass=pClass->m_pBaseClasss)
        {
            if(pClass->m_lpszClassName==s)
            {
                return pClass;
            }
        }
        return NULL;
    }
};

class AFX_CLASSINIT
{
public:
    AFX_CLASSINIT(CRuntimeClass*pNewClass)//構造函數
      {
         pNewClass->m_pNextClass=CRuntimeClass::pFirstClass;
        CRuntimeClass::pFirstClass =pNewClass;
      }
 };

/************************************************************************/
/* 動態類型識別宏定義
//與CRuntimeClass類中的構建函數相區別。此處的CreateObject函數在每個類中都以static成員函數存在，用以
//初始化類型型錄表，而CRuntimeClass中的CreateObject用於調用每個類的構建函數。僅僅是函數名相同罷了。*/
/************************************************************************/

#define DECLARE_DYNAMIC(class_name)\
     public:\
           static CRuntimeClass Class##class_name;\
           virtual CRuntimeClass*GetRuntimeClass()const;\


#define DECLARE_DYNCREATE(class_name)\
       DECLARE_DYNAMIC(class_name)\
       static CObject*PASCAL CreateObject();\

#define RUNTIME_CLASS(class_name)\
    (&class_name::Class##class_name)\

#define _IMPLEMENT_RUNTIMECLASS(class_name,base_class_name,wSchema,pfnNew)\
    class CRuntimeClass class_name::Class##class_name ={\
    #class_name,\
    sizeof(class_name),wSchema,pfnNew,RUNTIME_CLASS(base_class_name),NULL};\
    static AFX_CLASSINIT _init##class_name( RUNTIME_CLASS(class_name));\
    CRuntimeClass *class_name::GetRuntimeClass()const\
    {return &class_name::Class##class_name;}//此處將class_name寫成了classname花了一兩天才查出來。啊啊啊啊啊。20120605


#define IMPLEMENT_DYNAMIC(class_name,base_class_name)\
    _IMPLEMENT_RUNTIMECLASS(class_name,base_class_name,0xFFFF,NULL)\

#define IMPLEMENT_DYNCREATE(class_name,base_class_name)\
    CObject*PASCAL class_name::CreateObject(){return new class_name;}\
    _IMPLEMENT_RUNTIMECLASS(class_name,base_class_name,0xFFFF,class_name::CreateObject)\


/************************************************************************/
/*  對CObject特殊處理。                                                   */
/************************************************************************/
class CObject
{
public:
    CObject()
    {
        //cout<<"CObject constructor!"<<endl;
    }
    ~CObject()
    {
        //cout<<"CObject destructor!"<<endl;
    }
public:
    virtual CRuntimeClass*GetRuntimeClass();
    static CRuntimeClass  ClassCObject;
public:
    bool IsKindOf(CRuntimeClass*pClass)
    {
        CRuntimeClass *pThis=GetRuntimeClass();
        for(;pThis;pThis=pThis->m_pBaseClasss)
        {
            if(pThis==pClass)
            {
                return true;
            }
        }
        return false;
    }
};
class CRuntimeClass CObject:: ClassCObject=
{
   "CObject",sizeof(CObject),0xFFFF,NULL,NULL,NULL
};
static AFX_CLASSINIT _init_CObject(&CObject:: ClassCObject);
CRuntimeClass *CObject::GetRuntimeClass()
{
    return &CObject::ClassCObject;
}
CRuntimeClass*CRuntimeClass::pFirstClass=NULL;

/************************************************************************/
/* CCmdTarget是消息傳遞的終點，因此在實現時不能使用BEGIN_MESSAGE_MAP           */
/************************************************************************/
class CCmdTarget:public CObject
{
    DECLARE_DYNCREATE(CCmdTarget)
    DECLARE_MESSAGE_MAP()
public:
    CCmdTarget()
    {
        //cout<<"CCmdTarget constructor!"<<endl;
        //CreateObject();
    }
    ~CCmdTarget()
    {
        //cout<<"CCmdTarget destructor!"<<endl;
    }
public:


};
IMPLEMENT_DYNCREATE(CCmdTarget,CObject)

AFX_MSGMAP CCmdTarget::messageMap=
{NULL,CCmdTarget::_messageEntries};
AFX_MSGMAP_ENTRY CCmdTarget::_messageEntries[]=
{
    {0,0,10,0,AfxSig_end,0},
    {0,0,0,0,AfxSig_end,0}
};
AFX_MSGMAP*CCmdTarget::GetMessageMap()const
{
    return &CCmdTarget::messageMap;
}

class CWnd:public CCmdTarget
{
    DECLARE_DYNCREATE(CWnd)
    DECLARE_MESSAGE_MAP()
public:
    CWnd()
    {
        //cout<<"CWnd constructor"<<endl;
    }
    ~CWnd()
    {
        //cout<<"CWnd destructor"<<endl;
    }
public:
    virtual bool Create()
    {
        cout<<"CWnd::Create"<<endl;
        CreateEx();
        return true;
    }
    bool CreateEx()
    {
        cout<<"CWnd::CreateEx"<<endl;
        PreCreateWindow();
        return true;
    }
    virtual bool PreCreateWindow()
    {
        cout<<"CWnd::PreCreateWindow"<<endl;
        return true;
    }
};
IMPLEMENT_DYNCREATE(CWnd,CCmdTarget)

class CView :public CWnd
{
    DECLARE_DYNCREATE(CView)
    DECLARE_MESSAGE_MAP()
public:
    CView()
    {
        //cout<<"CView constructor"<<endl;

    }
    ~CView()
    {
        //cout<<"CView destructor"<<endl;
    }

};
IMPLEMENT_DYNCREATE(CView,CWnd)

class CFrameWnd:public CWnd
{
    DECLARE_DYNCREATE(CFrameWnd)
    DECLARE_MESSAGE_MAP()
public:
    CFrameWnd()
    {
        //cout<<"CFrameWnd constructor"<<endl;

    }
    ~CFrameWnd()
    {
        //cout<<"CFrameWnd destructor"<<endl;
    }
public:
    virtual bool Create()
    {
        cout<<"CFrameWnd::Create"<<endl;
        CreateEx();
        return true;
    }
    virtual bool PreCreateWindow()
    {
        cout<<"CFrameWnd::PreCreateWindow"<<endl;
        return true;
    }
};
IMPLEMENT_DYNCREATE(CFrameWnd,CWnd)

class CWinThread:public CCmdTarget
{
public:
    CWinThread()
    {
        //cout<<"CWinThread constructor"<<endl;
    }
    ~CWinThread()
    {
        //cout<<"CWinThread destructor"<<endl;
    }
public:
    virtual bool InitInstance()
    {
        cout<<"CWinThread::InitInstance"<<endl;
        return true;
    }
    virtual bool Run()
    {
        cout<<"CWinThread::Run"<<endl;
        return true;
    }
};
class CWinApp:public CWinThread
{
    DECLARE_MESSAGE_MAP()
public:
    CWinApp()
    {
        //cout<<"CWinApp Constructor "<<endl;
        m_currentApp=this;
    }
    ~CWinApp()
    {
        //cout<<"CWinApp destructor "<<endl;
    }
    virtual bool InitApplication()
    {
        cout<<"CWinApp::InitApplication"<<endl;
        return true;

    }
    virtual bool InitInstance()
    {
        cout<<"CWinApp:InitInstance"<<endl;
        return true;
    }
    virtual bool Run()
    {
        cout<<"CWinApp::Run"<<endl;
        return CWinThread::Run();
    }
public:
    CWinApp*m_currentApp;
    CFrameWnd*m_currentFrameWnd;
};
class CDocument:public CCmdTarget
{
    DECLARE_MESSAGE_MAP()
public:
    CDocument()
    {
        //cout<<"CDocument constructor "<<endl;
    }
    ~CDocument()
    {
        //cout<<"CDocunment destructor "<<endl;
    }
};
class CMyFrameWnd:public CFrameWnd
{
    DECLARE_DYNCREATE(CMyFrameWnd)
    DECLARE_MESSAGE_MAP()
public:
    CMyFrameWnd()
    {
        //cout<<"CMyFrameWnd constructor "<<endl;
        Create();
    }
    ~CMyFrameWnd()
    {
        //cout<<"CMyFrameWnd destructor "<<endl;
    }
};
IMPLEMENT_DYNCREATE(CMyFrameWnd,CFrameWnd)

class CMyWinApp:public CWinApp
{
    DECLARE_MESSAGE_MAP()
public:
    CMyWinApp()
    {
        //cout<<"CMyWinApp constructor "<<endl;

    }
    ~CMyWinApp()
    {
        //cout<<"CMyWinApp destructor "<<endl;
    }
public:
    bool InitInstance()
    {
        cout<<"CMyWinApp::InitInstance"<<endl;
        m_currentFrameWnd=new CMyFrameWnd;
        return true;
    }
};
BEGIN_MESSAGE_MAP(CWnd,CCmdTarget)
    ON_COMMAND(1,0)
END_MESSAGE_MAP()

BEGIN_MESSAGE_MAP(CFrameWnd,CWnd)
    ON_COMMAND(2,0)
END_MESSAGE_MAP()

BEGIN_MESSAGE_MAP(CDocument,CCmdTarget)
    ON_COMMAND(3,0)
END_MESSAGE_MAP()

BEGIN_MESSAGE_MAP(CView,CWnd)
    ON_COMMAND(4,0)
END_MESSAGE_MAP()

BEGIN_MESSAGE_MAP(CWinApp,CCmdTarget)
    ON_COMMAND(5,0)
END_MESSAGE_MAP()

BEGIN_MESSAGE_MAP(CMyWinApp,CWinApp)
    ON_COMMAND(6,0)
END_MESSAGE_MAP()

BEGIN_MESSAGE_MAP(CMyFrameWnd,CFrameWnd)
    ON_COMMAND(7,0)
END_MESSAGE_MAP()

CMyWinApp myApp;
CWinApp*AfxGetApp()
{
    return myApp.m_currentApp;
}
void printAllMsgMapping(AFX_MSGMAP*p)
{
    for(;p;p=p->pBaseMessageMap)
    {
        for(int i=0;p->lpEntries[i].nID;i++)
        {
            cout<<p->lpEntries[i].nID<<endl;
        }
    }
}

int main(int argc,char**argv)
{
    CWinApp *pApp=AfxGetApp();
    pApp->InitApplication();
    pApp->InitInstance();
    pApp->Run();

    CRuntimeClass *pClass;
    CObject *pOb;
    cout<<"以下爲類型型錄鏈表中的所有類的名稱："<<endl;
    for(pClass=CRuntimeClass::pFirstClass;pClass;pClass=pClass->m_pBaseClasss)
    {
        cout<<pClass->m_lpszClassName<<endl;
    }
    CMyFrameWnd *pMyFrame=(CMyFrameWnd*)pApp->m_currentFrameWnd;
    printAllMsgMapping(pMyFrame->GetMessageMap());
    cout<<endl;

    CDocument *pDoc=new CDocument;
    printAllMsgMapping(pDoc->GetMessageMap());

    while(1)
    {
        pClass=CRuntimeClass::Load();
        if(!pClass)
        {
            cout<<"找不到此類！！！"<<endl;
        }
        else
        {
            pOb=pClass->CreateObject();
            if(pOb)
            {
                cout<<"創建成功！"<<endl;
            }

        }
    }
    return 0;
}