复习总结《一》MFC消息映射

长时间人容易遗忘，从新捡起！特做下记录

MFC消息映射

1.在MFC中消息映射主要牵扯到三个宏分别为：

DECLARE_MESSAGE_MAP()
BEGIN_MESSAGE_MAP(theClass, baseClass)
END_MESSAGE_MAP()

2.先看源码

#define DECLARE_MESSAGE_MAP() \
protected: \
	static const AFX_MSGMAP* PASCAL GetThisMessageMap(); \
	virtual const AFX_MSGMAP* GetMessageMap() const; \

#define BEGIN_MESSAGE_MAP(theClass, baseClass) \
	const AFX_MSGMAP* theClass::GetMessageMap() const \
		{ return GetThisMessageMap(); } \
	const AFX_MSGMAP* PASCAL theClass::GetThisMessageMap() \
	{ \
		typedef theClass ThisClass;						   \
		typedef baseClass TheBaseClass;					   \
		static const AFX_MSGMAP_ENTRY _messageEntries[] =  \
		{

#define END_MESSAGE_MAP() \
		{0, 0, 0, 0, AfxSig_end, (AFX_PMSG)0 } \
	}; \
		static const AFX_MSGMAP messageMap = \
		{ &TheBaseClass::GetThisMessageMap, &_messageEntries[0] }; \
		return &messageMap; \
	}	

3.上述源码中牵扯到两个结构体分别为

struct AFX_MSGMAP_ENTRY
{
	UINT nMessage;   // windows message
	UINT nCode;      // control code or WM_NOTIFY code
	UINT nID;        // control ID (or 0 for windows messages)
	UINT nLastID;    // used for entries specifying a range of control id's
	UINT_PTR nSig;       // signature type (action) or pointer to message #
	AFX_PMSG pfn;    // routine to call (or special value)
};

struct AFX_MSGMAP
{
	const AFX_MSGMAP* (PASCAL* pfnGetBaseMap)();
	const AFX_MSGMAP_ENTRY* lpEntries;
};

包含两部分：1.函数指针(指向父类的获取AFX_MSGMAP的指针的静态函数)  2.AFX_MSGMAP_ENTRY结构体的指针

形成结构图

4.无论MFC中消息的走向如何(是向基类直接走还是横向走消息)，我们先必须把整个爬行路线网建立起来，即如上图就可以把基类和派生类连接起来。

作为消息基类CCmdTarget需要特殊处理，即CCmdTarget的父类的AFX_MSGMAP为NULL，CCmdTarget内的AFX_MSGMAP_ENTRY仅包含一项,       如下：

CCmdTarget类头文件包含

DECLARE_MESSAGE_MAP()

CCmdTarget类源文件有

const AFX_MSGMAP* CCmdTarget::GetMessageMap() const
{
	return GetThisMessageMap();
}

const AFX_MSGMAP* CCmdTarget::GetThisMessageMap()
{
	static const AFX_MSGMAP_ENTRY _messageEntries[] =
	{
		{ 0, 0, AfxSig_end, 0 }     // nothing here
	};
	static const AFX_MSGMAP messageMap =
	{
		NULL,
		&_messageEntries[0]
	};
	return &messageMap;
}

简化版本:

#ifndef __DEFINE_H__
#define __DEFINE_H__

typedef void (*CALL_MSG)(int wParam, int lParam);

struct MSG_MAP_ENTRY
{
    unsigned int nMessage;    //消息类型
    unsigned int nSig;        // 信号类型
    CALL_MSG pfn;             //回调函数，即处理函数
};

struct MSG_MAP
{
    MSG_MAP* (*pfnGetBaseMap)();
    MSG_MAP_ENTRY* lpEntries;
};

#define DECLARE_MESSAGE_MAP()                                   \
        static const  MSG_MAP*  GetThisMessageMap();      \
        virtual const  MSG_MAP* GetMessageMap();

#define BEGIN_MESSAGE_MAP(theClass, baseClass)                  \
        const MSG_MAP*  theClass::GetMessageMap(){                \
            return GetThisMessageMap();                         \
        }                                                       \
        const MSG_MAP*  theClass::GetThisMessageMap()            \
        {                                                       \
            typedef theClass ThisClass;                         \
            typedef baseClass TheBaseClass;                     \
            static const MSG_MAP_ENTRY _messageEntries[] =                     \
            {

#define END_MESSAGE_MAP()                                               \
                {0, 0, (CALL_MSG)0 }                  \
            };                                                          \
            static const AFX_MSGMAP messageMap =                        \
            { &TheBaseClass::GetThisMessageMap, &_messageEntries[0] };  \
            return &messageMap;                                         \
        }

#endif