请教一个键盘钩子的问题 VC

Nova223 2014-04-10 10:37:19

今天自己琢磨了一下，写了一个全局键盘钩子，能实现对A键的屏蔽以及重定位（keybd_event) 但是有两个问题，第一个是每一次敲击键盘A 似乎callback function都会被call两次，导致一次A会产生两个B的keybd event 当然也会printf两次。请问这是为什么？

第二是，我听说全局键盘钩子都需要dll，可是我并没有用dll，执行程序之后也可以起到全局键盘钩子的作用，我理解是因为WH_KEYBOARD_LL，但不知道为什么这个参数可以起到全局的作用？不通过DLL 其他进程如何被注入呢？

程序如下，感谢！



// GlobalHook.cpp : Defines the entry point for the console application.

//



#include "stdafx.h"

#include <Windows.h>

#define _WIN32_WINNT 0x050



LRESULT CALLBACK LowLevelKeyboardProc(int nCode, WPARAM wParam, LPARAM lParam)

{

	BOOL fEatKeystroke = FALSE;



	if (nCode == HC_ACTION)

	{

		switch (wParam)

		{

		case WM_KEYDOWN:

		case WM_SYSKEYDOWN:

		case WM_KEYUP:

		case WM_SYSKEYUP:

			PKBDLLHOOKSTRUCT p = (PKBDLLHOOKSTRUCT)lParam;



			if (fEatKeystroke = (p->vkCode == 0x41)) {     //redirect a to b

				printf("Hello a\n");

				keybd_event('B', 0, 0, 0);

				keybd_event('B', 0, KEYEVENTF_KEYUP, 0);

				break;

			}

			break;

		}

	}

	return(fEatKeystroke ? 1 : CallNextHookEx(NULL, nCode, wParam, lParam));

}



int main()

{

	// Install the low-level keyboard & mouse hooks

	HHOOK hhkLowLevelKybd = SetWindowsHookEx(WH_KEYBOARD_LL, LowLevelKeyboardProc, 0, 0);



	// Keep this app running until we're told to stop

	MSG msg;

	while (!GetMessage(&msg, NULL, NULL, NULL)) {    //this while loop keeps the hook

		TranslateMessage(&msg);

		DispatchMessage(&msg);

	}



	UnhookWindowsHookEx(hhkLowLevelKybd);



	return(0);

}