仅在按下键时调用函数，而不是在释放键时调用

Question

当下面的 sn-p 运行时，每次点击一个键，都会调用函数 LowLevelKeyboardProc。但问题是它在按下一个键时和释放一个键时都被调用。这意味着，每次点击该函数被调用两次。但是我希望该函数在键被调用时只被调用一次按下而不是在释放键时。

即使我可以在函数 LowLevelKeyboardProc 中过滤按键的按下和释放，也没问题。有什么办法可以做到这一点。

static LRESULT CALLBACK LowLevelKeyboardProc(int nCode, WPARAM wParam, LPARAM lParam) {
  // call the function only if the key is pressed,else ( i.e key released) do nothing
}

BOOL WINAPI installHook(HINSTANCE hinstDLL, DWORD fwdReason, LPVOID lpvReserved){
  handleKeyboardHook = SetWindowsHookEx(WH_KEYBOARD_LL, LowLevelKeyboardProc, hinstDLL, 0);
  MSG msg;

  while(GetMessage(&msg, NULL, 0, 0)){
    TranslateMessage(&msg);
    DispatchMessage(&msg);
  }
  return msg.wParam;
}

BOOL WINAPI DllMain( HINSTANCE hinstDLL, DWORD fwdReason, LPVOID lpvReserved) { // ENTRY POINT
 if(hookThreadHandle==NULL) { 
    LPTHREAD_START_ROUTINE lpStartAddress = &installHook;
    hookThreadHandle = CreateThread(NULL, 0, lpStartAddress, NULL, 0, &hookThreadId);
 }
 return TRUE;
}

Answer 1

你不能改变LowLevelKeyboardProc的调用方式，但在函数内部你可以知道调用的原因：

static LRESULT CALLBACK LowLevelKeyboardProc(int nCode, WPARAM wParam, LPARAM lParam) 
{
     if ( nCode < 0 )
     {
         return CallNextHookEx(handleKeyboardHook, nCode, wParam, lParam);
     }

     if ( wParam == WM_KEYDOWN )  // possibly you want also WM_SYSKEYDOWN
     {
         // do what you need
     }
}