BEGIN_MESSAGE_MAP 和END_MESSAGE_MAP() 这两个宏的具体实现与作用

BEGIN_MESSAGE_MAP和END_MESSAGE_MAP
首先看定义
#define BEGIN_MESSAGE_MAP(theClass, baseClass) /
      const AFX_MSGMAP* theClass::GetMessageMap() const /
            { return &theClass::messageMap; } /
      AFX_COMDAT AFX_DATADEF const AFX_MSGMAP theClass::messageMap = /
      { &baseClass::messageMap, &theClass::_messageEntries[0] }; /
      AFX_COMDAT const AFX_MSGMAP_ENTRY theClass::_messageEntries[] = /
      { /
实际应用BEGIN_MESSAGE_MAP(myview,CView)等价于
      const AFX_MSGMAP* myview::GetMessageMap() const /
            { return & myview::messageMap; } /
      AFX_COMDAT AFX_DATADEF const AFX_MSGMAP myview::messageMap = /
      { & CView::messageMap, & myview::_messageEntries[0] }; /
      AFX_COMDAT const AFX_MSGMAP_ENTRY myview::_messageEntries[] = /
      { /
END_MESSAGE_MAP和BEGIN_MESSAGE_MAP是成对出现的
#define END_MESSAGE_MAP() /
            {0, 0, 0, 0, AfxSig_end, (AFX_PMSG)0 } /
      }; /
class myview:public CView
{
public:
      static const CRuntimeClass classmyview;
      virtual CRuntimeClass* GetRuntimeClass() const;
      static CObject* __stdcall CreateObject();
public:
      void OnDraw(CDC *d)
      {
            mydoc *b;
            b=(mydoc *)m_pDocument;
            d->SetTextColor(RGB(0,0,0)) ;
            d->TextOut(b->point.x,b->point.y ,b->s) ;
           
      }
     
      void OnLButtonDown(UINT nFlags,CPoint p)
      {
            mydoc *b;
            b=(mydoc*)m_pDocument;
            b->point.x=p.x;
            b->point.y=p.y;
            Invalidate();
      }
private:
              static const AFX_MSGMAP_ENTRY _messageEntries[];
protected:
              static AFX_DATA const AFX_MSGMAP messageMap;
              virtual const AFX_MSGMAP* GetMessageMap() const;          
};
 
CObject* __stdcall myview::CreateObject()
{ return new myview; }
 
const CRuntimeClass myview::classmyview =
{
      "myview", sizeof(class myview), 0xFFFF, myview::CreateObject,
            (CRuntimeClass*)(& CView::classCView), NULL
};
CRuntimeClass* myview::GetRuntimeClass() const
{
      return ((CRuntimeClass*)(& myview::classmyview));
}
 
const AFX_MSGMAP* myview::GetMessageMap() const
{ return & myview::messageMap; }
 
 const AFX_MSGMAP myview::messageMap =
{ & CView::messageMap, & myview::_messageEntries[0] };
 
 const AFX_MSGMAP_ENTRY myview::_messageEntries[] =
{
 
     {
     WM_LBUTTONDOWN, 0, 0, 0, AfxSig_vwp,
     (AFX_PMSG)(AFX_PMSGW)(void (CWnd::*)(UINT, CPoint))&OnLButtonDown
     },
          
 {0, 0, 0, 0, AfxSig_end, (AFX_PMSG)0 }
 
};
 
DECLARE_MESSAGE_MAP、BEGIN_MESSAGE_MAP、END_MESSAGE_MAP以及ON_COMMAND、ON_MESSAGE等宏最终作用的结果是在你的类中生成了一个名为lpEntries的数组，该数组中将填入每个你关心的消息和此消息对应的处理函数。应用程序框架生成的WindowProc接收到一个消息后，会按照一定的原则轮询个各类（CView、CDocument、CFrameWnd、CWinApp）的messageEntries数组，检查该数组中有没有对应的消息，如果有，就调用相应的响应函数；如果没有，就换下一个类继续检查。当所有的有关的类都被检查完后仍未发现响应函数时，便将此消息丢给DefWindowProc处理。  
      MFC之所以这样做，主要是考虑到使用虚函数会造成过大的系统开销。以上只是实现的简单原理，详细过程你还是去看MFC的源代码吧。我个人认为，MFC在消息处理这事上，做得还是相当漂亮。 有关进一步的资料请自己查询有关MFC的书籍