HOOK使用:全局键盘钩子

// CatchKey.cpp : Defines the entry point for the DLL application.
//

#define _WIN32_WINNT  0x0500        //设置系统版本，可以使用底层键盘钩子
#define WM_MY_SHORTS (WM_USER + 105)
#include "windows.h"
//全局变量 
LPWORD		g_lpdwVirtualKey = NULL;    //Keycode 数组的指针 
int         g_nLength = 0;          //Keycode 数组的大小 
HINSTANCE   g_hInstance = NULL;     //模块实例句柄  
HHOOK       g_hHook = NULL;         //钩子句柄 
HWND        g_hWnd  = NULL;  


BOOL APIENTRY DllMain(HANDLE hModule, DWORD  ul_reason_for_call,LPVOID lpReserved) 
{  
	//保存模块实例句柄 
	g_hInstance = (HINSTANCE)hModule; 
	
	//在进程结束或线程结束时卸载钩子  
	switch (ul_reason_for_call) 
	{ 
	case DLL_PROCESS_ATTACH: 
     	   break;  
	case DLL_THREAD_ATTACH:
   	     break; 	
	case DLL_PROCESS_DETACH: 
	  case DLL_THREAD_DETACH:  
		delete g_lpdwVirtualKey;  
        if (g_hHook != NULL) UnhookWindowsHookEx(g_hHook); 
		break;
    }
	return TRUE;
}  

LRESULT CALLBACK LowLevelKeyboardProc(int nCode, WPARAM wParam,LPARAM lParam)
{ 
	//判断是否是有效按键
    if (nCode >= HC_ACTION && wParam==WM_KEYDOWN) 
	{ 
		BOOL bctrl = GetAsyncKeyState(VK_CONTROL)>>((sizeof(SHORT) *8)-1);   
		KBDLLHOOKSTRUCT* pStruct = (KBDLLHOOKSTRUCT*)lParam;  
		LPWORD tmpVirtualKey = g_lpdwVirtualKey;  
		if (pStruct->vkCode == 80 && bctrl)  
			PostMessage(g_hWnd,WM_MY_SHORTS,0,1);  
        return TRUE;  
	} 
    //传给系统中的下一个钩子 
	return CallNextHookEx(g_hHook, nCode, wParam, lParam); 
}  

 _declspec(dllexport)
BOOL WINAPI StartCatch(LPWORD lpdwVirtualKey, int nLength,  HWND  pWnd) 
{  
	g_hWnd = pWnd;  
	//如果已经安装键盘钩子则返回 FALSE  
	if (g_hHook != NULL) return FALSE;
	//将用户传来的 keycode 数组保存在全局变量中 
	g_lpdwVirtualKey = (LPWORD)malloc(sizeof(WORD) * nLength); 
	LPWORD tmpVirtualKey = g_lpdwVirtualKey; 
	for (int i = 0; i < nLength; i++)  
	{ 
		*tmpVirtualKey++ = *lpdwVirtualKey++; 
	} 
	g_nLength = nLength;  
	//安装底层键盘钩子  
	g_hHook = SetWindowsHookEx(WH_KEYBOARD_LL, LowLevelKeyboardProc,  g_hInstance, NULL);  
	if (g_hHook == NULL) return FALSE; 
	return TRUE;  
}  

 _declspec(dllexport)
BOOL WINAPI StopCatch() 
{   //卸载钩子 
	if (UnhookWindowsHookEx(g_hHook) == 0) return FALSE; 
	g_hHook = NULL; 
	return TRUE; 
 }  

利用底层的键盘钩子
LRESULT CALLBACK LowLevelKeyboardProc(int nCode, WPARAM wParam,LPARAM lParam)
来拦截 按键的时候

键盘的键按下和弹起时候会发生WM_KEYUP 和 WM_KEYDOWN两个消息，
这两个消息都会被hook，所以如此。

所以需要对 wParam 进行判断 是 WM_KEYDOWN 还是 WM_KEYUP