Question

hook键盘钩子后，怎么判断按键是系统的左右哪一个键

Answer 1

可以从LPARAM参数中提取出虚拟键值(virtual key)，代码片段如下：
C/C++ codePKBDLLHOOKSTRUCT p = (PKBDLLHOOKSTRUCT) (lParam);
if (wParam == WM_KEYDOWN)
{
char* buf;
char tl[256];
buf = tl;
buf = itoa(p->vkCode,buf,10);//这句是关键
int tmp;
tmp = atoi(buf);
switch (tmp)
{
//......
case VK_LMENU: buf = "<Left MENU>"; break;
//......
}
}
------解决方案--------------------
可以从LPARAM参数中提取出虚拟键值(virtual key)，代码片段如下：
C/C++ codePKBDLLHOOKSTRUCT p = (PKBDLLHOOKSTRUCT) (lParam);
if (wParam == WM_KEYDOWN)
{
char* buf;
char tl[256];
buf = tl;
buf = itoa(p->vkCode,buf,10);//这句是关键
int tmp;
tmp = atoi(buf);
switch (tmp)
{
//......
case VK_LMENU: buf = "<Left MENU>"; break;
//......
}
}
------解决方案--------------------
我在PreTranslateMessage中截获消息，并处理Key值，可以区分开始左边还是右边的按下。
例如左shift还是右shift，但是令我感到奇怪的一点是alt键不是在WM_KEYDOWN中响应，而是在WM_SYSKEYDOWN中响应，而且每按两次才会相应一次，但是区分左右还是没问题的，直接上代码；
C/C++ code在PreTranslateMessage中处理如下代码

BYTE vKeyArrow[256];

switch(pMsg->message)
{
case WM_KEYDOWN:
memset(vKeyArrow,0,256);
GetKeyboardState(vKeyArrow);
if (vKeyArrow[0xa0] == 0x80 || vKeyArrow[0xa0] == 0x81)
TRACE(L"Left shift is down\n");//左Shift键按下
if (vKeyArrow[0xa1] == 0x80 || vKeyArrow[0xa1] == 0x81)
TRACE(L"Right shift is down\n");//右Shift键按下
break;
case WM_SYSKEYDOWN:
memset(vKeyArrow,0,256);
GetKeyboardState(vKeyArrow);
if (vKeyArrow[0xa4] == 0x80 || vKeyArrow[0xa4] == 0x81)
TRACE(L"Left alt is down\n");//左alt键按下
if (vKeyArrow[0xa5] == 0x80 || vKeyArrow[0xa5] == 0x81)
TRACE(L"Right alt is down\n");//右alt键按下
break;
}
------解决方案--------------------
C/C++ codeLRESULT CALLBACK LowLevelKeyboardProc(int nCode, WPARAM wParam, LPARAM lParam)
{
if(HC_ACTION == nCode)
{
KBDLLHOOKSTRUCT* pSturct = (KBDLLHOOKSTRUCT*)lParam;

switch(wParam)
{
case WM_SYSKEYDOWN:
switch(pSturct->vkCode)
{
case VK_LMENU:
AfxMessageBox(_T("Left ALT"));
break;

case VK_RMENU:
AfxMessageBox(_T("Right ALT"));
break;
}
break;

default:
break;
}
}
return CallNextHookEx(hOldHook, nCode, wParam, lParam);
}