Windows Hook 学习笔记（2）——键盘挂钩

      本例是C#编写的，演示如果设置键盘Hook，拦截键盘按键操作，并返回按键的键值。

 1using System;
 2using System.Runtime.InteropServices;
 3using System.Windows.Forms;
 4
 5namespace Hook
 6{
 7    public partial class Form1 : Form
 8    {
 9        public delegate IntPtr HookProc(int nCode, Int32 wParam, IntPtr lParam);
10
11        Win32 API#region Win32 API
12
13        //设置挂钩
14        [DllImport("user32.dll", CharSet = CharSet.Auto, CallingConvention = CallingConvention.StdCall)]
15        public static extern IntPtr SetWindowsHookEx(int idHook, HookProc lpfn, IntPtr hInstance, int threadId);
16        //调用下一个钩子
17        [DllImport("user32.dll", CharSet = CharSet.Auto, CallingConvention = CallingConvention.StdCall)]
18        public static extern IntPtr CallNextHookEx(IntPtr idHook, int nCode, Int32 wParam, IntPtr lParam);
19        //移除挂钩
20        [DllImport("user32.dll", CharSet = CharSet.Auto, CallingConvention = CallingConvention.StdCall)]
21        public static extern bool UnhookWindowsHookEx(IntPtr idHook);
22        //获取当前进程的编号
23        [DllImport("kernel32.dll")]
24        public static extern int GetCurrentThreadId();
25        //获取按键的状态
26        [DllImport("user32")]
27        public static extern short GetKeyState(int vKey);
28
29        #endregion
30
31        private IntPtr hookKeyBoard = IntPtr.Zero;
32        private HookProc hpKeyBoard;
33        private int WH_KEYBOARD = 2;
34
35        public event KeyEventHandler KeyDownEvent;
36
37        public Form1()
38        {
39            InitializeComponent();
40
41            hpKeyBoard = new HookProc(KeyboardHookProc);
42            //这里设置为拦截当前进程中键盘按键，使用的Hook常数是WH_KEYBOARD（数值为2）；
43            //GetCurrentThreadId()是当前进程的编号。也可以使用 AppDomain.GetCurrentThreadId()，但在.Net 2.0中已被标示为“过时”。
44            //如果要在任何时候都能够拦截按键（不管目前激活的窗口是否是当前进程），就要设置全局Hook，对应的hook常数是 WH_KEYBOARD_LL（数值为13）。
45            hookKeyBoard = SetWindowsHookEx(WH_KEYBOARD, hpKeyBoard, (IntPtr)0, GetCurrentThreadId());
46
47            this.KeyDownEvent += new KeyEventHandler(Form1_KeyDownEvent);
48        }
49
50        void Form1_KeyDownEvent(object sender, KeyEventArgs e)
51        {
52            MessageBox.Show(e.KeyData.ToString());
53        }
54
55        private IntPtr KeyboardHookProc(int nCode, Int32 wParam, IntPtr lParam)
56        {
57            bool isPressed = (lParam.ToInt32() & 0x80000000) == 0;
58
59            if (nCode < 0 || !isPressed)
60            {
61                return CallNextHookEx(hookKeyBoard, nCode, wParam, lParam);
62            }
63
64            if (KeyDownEvent != null && (GetKeyState(wParam) >> 0x10) == 0)
65            {
66                Keys keyData = (Keys)wParam;
67                KeyEventArgs e = new KeyEventArgs(keyData);
68                KeyDownEvent(this, e);
69            }
70            return CallNextHookEx(hookKeyBoard, nCode, wParam, lParam);
71        }
72
73        private void Form1_FormClosing(object sender, FormClosingEventArgs e)
74        {
75            UnhookWindowsHookEx(hookKeyBoard);
76            hookKeyBoard = IntPtr.Zero;
77        }
78    }
79}