关于最近给一家企业做的文档保全系统的技术整理（3）

4、全局键盘钩子

如果程序需要监视键盘的按键动作，那么最好的方法就是使用键盘钩子程序。

钩子程序首先需要一个键盘钩子结构体

   //键盘钩子结构体
    [StructLayout(LayoutKind.Sequential)]
    public struct KeyBoardDllHookStruct
    {
        public int vkCode;
        public int scanCode;
        public int flags;
        public int time;
        public int dwExtraInfo;
    }

键盘钩子的事件

    //键盘钩子事件
    public class KeyboardHookEventArgs : System.EventArgs
    {

        private string keyName;
        private int keyCode;
        private bool passThrough;

        /// <summary>
        /// The name of the key that was pressed.
        /// </summary>
        public string KeyName
        {
            get { return keyName; }
        }


        public int KeyCode
        {
            get { return keyCode; }
        }

        public bool PassThrough
        {
            get { return passThrough; }
        }

        public KeyboardHookEventArgs(int evtKeyCode, bool evtPassThrough)
        {
            keyName = ((Keys)evtKeyCode).ToString();
            keyCode = evtKeyCode;
            passThrough = evtPassThrough;
        }

    }

钩子：

 public class KeyBoardHook
    {
        private static IntPtr hookID = IntPtr.Zero;
        private const int WM_KEYDOWN = 0x0100;
        private const int WM_KEYUP = 0x0101;
        private const int WH_KEYBOARD_LL = 13;
        private const int WM_SYSKEYDOWN = 0x0104;
        private const int WM_SYSKEYUP = 0x0105;
        private static bool PassAllKeysToNextApp = true;
        public delegate IntPtr HookHandlerDelegate(int nCode, IntPtr wParam, ref KeyBoardDllHookStruct lParam);
        public delegate void KeyboardHookEventHandler(KeyboardHookEventArgs e);
        public static event KeyboardHookEventHandler KeyDownEvent;
        public static event KeyboardHookEventHandler KeyUpEvent;
        private static HookHandlerDelegate proc;
        private delegate IntPtr HookProc(
         int nCode,
         IntPtr wParam,
         ref KeyBoardDllHookStruct lParam
     );

        //注册键盘钩子
        public static void KeyBoardDllHookStart()
        {
           
            proc = new HookHandlerDelegate(HookCallback);
            using (Process curProcess = Process.GetCurrentProcess())
            {
                using (ProcessModule curModule = curProcess.MainModule)
                {
                    hookID = Win32API.SetWindowsHookEx(WH_KEYBOARD_LL, proc,
                        Win32API.GetModuleHandle(curModule.ModuleName), 0);
                }
            }
        }


        //卸载键盘钩子
        public static void KeyBoardDllHookStop()
        {
            if (hookID != IntPtr.Zero)
            {
                Win32API.UnhookWindowsHookEx(hookID);
            }
        }

        //激发事件
        private static void OnKeyDown(KeyboardHookEventArgs e)
        {
            if (KeyDownEvent != null)
                KeyDownEvent(e);
        }

        //激发事件
        private static void OnKeyUp(KeyboardHookEventArgs e)
        {
            if (KeyUpEvent != null)
                KeyUpEvent(e);
        }


        private static IntPtr HookCallback(int nCode, IntPtr wParam, ref KeyBoardDllHookStruct lParam)
        {
          bool AllowKey = PassAllKeysToNextApp;

            //过滤wParam的KeyDown事件
            if (nCode >= 0 && (wParam == (IntPtr)WM_KEYDOWN || wParam == (IntPtr)WM_SYSKEYDOWN))
            {
                AllowKey = true;
                OnKeyDown(new KeyboardHookEventArgs(lParam.vkCode, AllowKey));
                if (AllowKey)
                {
                    return Win32API.CallNextHookEx(hookID, nCode, wParam, ref lParam);
                }
                else
                {
                    return (System.IntPtr)1;
                }
            }

            //过滤wParam的KeyUp事件
            if (nCode >= 0 && (wParam == (IntPtr)WM_KEYUP || wParam == (IntPtr)WM_SYSKEYUP))
            {
                AllowKey = true; ;
                OnKeyUp(new KeyboardHookEventArgs(lParam.vkCode, AllowKey));
                if (AllowKey)
                {
                    return Win32API.CallNextHookEx(hookID, nCode, wParam, ref lParam);
                }
                else
                {
                    return (System.IntPtr)1;
                }
            }

            return Win32API.CallNextHookEx(hookID, nCode, wParam, ref lParam);

        }

    }

该类提供了两个事件KeyDownEvent和KeyUpEvent分别在按下和释放时激发，大家可以通过这两个事件添加自己的处理程序。

在程序的适当入口通过调用该类的KeyBoardDllHookStart方法注册该钩子程序。关闭的时候调用KeyBoardDllHookStop方法卸载钩子。

例如：我在程序主窗体的构造函数中注册

            //注册键盘钩子
            KeyBoardHook.KeyBoardDllHookStart();
            KeyBoardHook.KeyDownEvent += new KeyBoardHook.KeyboardHookEventHandler(KeyBoardHook_KeyDownEvent);
            KeyBoardHook.KeyUpEvent += new KeyBoardHook.KeyboardHookEventHandler(KeyBoardHook_KeyUpEvent);