C# 鈎子函數使用

1. 什么是鈎子

hook（鈎子）是windows提供的一種消息處理機制平台，是指在程序正常運行中接受信息之前預先啟動的函數，用來檢查和修改傳給該程序的信息，（鈎子）實際上是一個處理消息的程序段，通過系統調用，把它掛入系統。每當特定的消息發出， 在沒有到達目的窗口前，鈎子程序就先捕獲該消息，亦即鈎子函數先得到控制權。這時鈎子函數即可以加工處理（改變）該消息，也可以不作處理而繼續傳遞該消息，還可以強制結束消息的傳遞(return)。

2. 鈎子函數的聲明

C#是.NET Framework平台的相伴語言，用它本身的類庫和編譯器提供的方法是無法實現全局鈎子的。但實際上對於非托管代碼的調用在C#中是成立的，鈎子函數存在於user32.dll中，使用DllImport屬性可以引用非托管代碼類庫中的方法。

鈎子函數的安裝：

  //安裝鈎子
        [DllImport("user32.dll", CharSet = CharSet.Auto, CallingConvention = CallingConvention.StdCall)]

        public static extern int SetWindowsHookEx(int idHook, HookProc lpfn, IntPtr hInstance, int threadId);

鈎子函數卸載：

        //卸載鈎子
        [DllImport("user32.dll", CharSet = CharSet.Auto, CallingConvention = CallingConvention.StdCall)]

        public static extern bool UnhookWindowsHookEx(int idHook);

鈎子函數使用：

        //調用下一個鈎子
        [DllImport("user32.dll", CharSet = CharSet.Auto, CallingConvention = CallingConvention.StdCall)]

        public static extern int CallNextHookEx(int idHook, int nCode, IntPtr wParam, IntPtr lParam);

3.鈎子函數的使用

首先聲明一個委托：

        //委托+事件（把鈎到的消息封裝為事件，由調用者處理）

        public delegate void MouseMoveHandler(object sender, MouseEventArgs e);

        public event MouseMoveHandler MouseMoveEvent;

定義一個鼠標鈎子類：

    public class MouseHook
    {

        private Point point;

        private Point Point
        {

            get { return point; }

            set
            {
                if (point != value)
                {
                    point = value;
                    if (MouseMoveEvent != null)
                    {
                        var e = new MouseEventArgs(MouseButtons.None, 0, point.X, point.Y, 0);
                        MouseMoveEvent(this, e);
                    }
                }
            }
        }

        private int hHook;

        public const int WH_MOUSE_LL = 14;

        public Win32Api.HookProc hProc;

        public MouseHook() { this.Point = new Point(); }

        public int SetHook()
        {

            hProc = new Win32Api.HookProc(MouseHookProc);

            hHook = Win32Api.SetWindowsHookEx(WH_MOUSE_LL, hProc, IntPtr.Zero, 0);

            return hHook;

        }

        public void UnHook()
        {

            Win32Api.UnhookWindowsHookEx(hHook);

        }

        private int MouseHookProc(int nCode, IntPtr wParam, IntPtr lParam)
        {

            Win32Api.MouseHookStruct MyMouseHookStruct = (Win32Api.MouseHookStruct)Marshal.PtrToStructure(lParam, typeof(Win32Api.MouseHookStruct));

            if (nCode < 0)
            {

                return Win32Api.CallNextHookEx(hHook, nCode, wParam, lParam);

            }

            else
            {

                this.Point = new Point(MyMouseHookStruct.pt.x, MyMouseHookStruct.pt.y);

                return Win32Api.CallNextHookEx(hHook, nCode, wParam, lParam);

            }

        }

        //委托+事件（把鈎到的消息封裝為事件，由調用者處理）

        public delegate void MouseMoveHandler(object sender, MouseEventArgs e);

        public event MouseMoveHandler MouseMoveEvent;

    }

調用鈎子：

   public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }
        MouseHook mh;

        private void Form1_Load(object sender, EventArgs e)
        {

            mh = new MouseHook();

            mh.SetHook();

            mh.MouseMoveEvent += mh_MouseMoveEvent;

        }

        void mh_MouseMoveEvent(object sender, MouseEventArgs e)
        {

            int x = e.Location.X;

            int y = e.Location.Y;

            label1.Text = string.Format("當前鼠標位置為：（{0}，{1}）", x, y);

        }

        private void Form1_FormClosed(object sender, FormClosedEventArgs e)
        {

            mh.UnHook();
        }
    }

Win32Api 導入類：

需要引入 using System.Runtime.InteropServices; 命名空間

public class Win32Api
    {

        [StructLayout(LayoutKind.Sequential)]
        public class POINT
        {
            public int x;

            public int y;

        }

        [StructLayout(LayoutKind.Sequential)]
        public class MouseHookStruct
        {

            public POINT pt;

            public int hwnd;

            public int wHitTestCode;

            public int dwExtraInfo;

        }

        public delegate int HookProc(int nCode, IntPtr wParam, IntPtr lParam);

        //安裝鈎子
        [DllImport("user32.dll", CharSet = CharSet.Auto, CallingConvention = CallingConvention.StdCall)]

        public static extern int SetWindowsHookEx(int idHook, HookProc lpfn, IntPtr hInstance, int threadId);

        //卸載鈎子
        [DllImport("user32.dll", CharSet = CharSet.Auto, CallingConvention = CallingConvention.StdCall)]

        public static extern bool UnhookWindowsHookEx(int idHook);

        //調用下一個鈎子
        [DllImport("user32.dll", CharSet = CharSet.Auto, CallingConvention = CallingConvention.StdCall)]

        public static extern int CallNextHookEx(int idHook, int nCode, IntPtr wParam, IntPtr lParam);

    }

運行結果：

 

 鼠標在窗口移動的時候，顯示鼠標當前的坐標位置（在整個顯示屏幕中的坐標）。