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用钩子(hook)实现C#的屏幕键盘效果

        要实现一个屏幕键盘,需要监听所有键盘事件,无论窗体是否被激活。因此需要一个全局的钩子,也就
是系统范围的钩子。

什么是钩子(Hook)

       钩子(Hook)是Windows提供的一种消息处理机制平台,是指在程序正常运行中接受信息之前预先启动的函数,用来检查和修改传给该程序的信息,(钩子)实际上是一个处理消息的程序段,通过系统调用,把它挂入系统。每当特定的消息发出,在没有到达目的窗口前,钩子程序就先捕获该消息,亦即钩子函数先得到控制权。这时钩子函数即可以加工处理(改变)该消息,也可以不作处理而继续传递该消息,还可以强制结束消息的传递。注意:安装钩子函数将会影响系统的性能。监测“系统范围事件”的系统钩子特别明显。因为系统在处理所有的相关事件时都将调用您的钩子函数,这样您的系统将会明显的减慢。所以应谨慎使用,用完后立即卸载。还有,由于您可以预先截获其它进程的消息,所以一旦您的钩子函数出了问题的话必将影响其它的进程。

钩子的作用范围

       一共有两种范围(类型)的钩子,局部的和远程的。局部钩子仅钩挂自己进程的事件。远程的钩子还可以将钩挂其它进程发生的事件。远程的钩子又有两种: 基于线程的钩子将捕获其它进程中某一特定线程的事件。简言之,就是可以用来观察其它进程中的某一特定线程将发生的事件。系统范围的钩子将捕捉系统中所有进程将发生的事件消息。 

Hook 类型

       Windows共有14种Hooks,每一种类型的Hook可以使应用程序能够监视不同类型的系统消息处理机制。下面描述所有可以利用的Hook类型的发生时机。详细内容可以查阅MSDN,这里只介绍我们将要用到的两种类型的钩子。

(1)WH_KEYBOARD_LL Hook

WH_KEYBOARD_LL Hook监视输入到线程消息队列中的键盘消息。

(2)WH_MOUSE_LL Hook

WH_MOUSE_LL Hook监视输入到线程消息队列中的鼠标消息。

下面的 class 把 API 调用封装起来以便调用。

1// NativeMethods.cs
2using System;
3using System.Runtime.InteropServices;
4using System.Drawing;
5
6namespace CnBlogs.Youzai.ScreenKeyboard {
7    [StructLayout(LayoutKind.Sequential)]
8    internal struct MOUSEINPUT {
9        public int dx;
10        public int dy;
11        public int mouseData;
12        public int dwFlags;
13        public int time;
14        public IntPtr dwExtraInfo;
15    }
16
17    [StructLayout(LayoutKind.Sequential)]
18    internal struct KEYBDINPUT {
19        public short wVk;
20        public short wScan;
21        public int dwFlags;
22        public int time;
23        public IntPtr dwExtraInfo;
24    }
25
26    [StructLayout(LayoutKind.Explicit)]
27    internal struct Input {
28        [FieldOffset(0)]
29        public int type;
30        [FieldOffset(4)]
31        public MOUSEINPUT mi;
32        [FieldOffset(4)]
33        public KEYBDINPUT ki;
34        [FieldOffset(4)]
35        public HARDWAREINPUT hi;
36    }
37
38    [StructLayout(LayoutKind.Sequential)]
39    internal struct HARDWAREINPUT {
40        public int uMsg;
41        public short wParamL;
42        public short wParamH;
43    }
44
45    internal class INPUT {
46        public const int MOUSE = 0;
47        public const int KEYBOARD = 1;
48        public const int HARDWARE = 2;
49    }
50
51    internal static class NativeMethods {
52        [DllImport("User32.dll", CharSet = CharSet.Auto, SetLastError = false)]
53        internal static extern IntPtr GetWindowLong(IntPtr hWnd, int nIndex);
54
55        [DllImport("User32.dll", CharSet = CharSet.Auto, SetLastError = false)]
56        internal static extern IntPtr SetWindowLong(IntPtr hWnd, int nIndex, int dwNewLong);
57
58        [DllImport("User32.dll", EntryPoint = "SendInput", CharSet = CharSet.Auto)]
59        internal static extern UInt32 SendInput(UInt32 nInputs, Input[] pInputs, Int32 cbSize);
60
61        [DllImport("Kernel32.dll", EntryPoint = "GetTickCount", CharSet = CharSet.Auto)]
62        internal static extern int GetTickCount();
63
64        [DllImport("User32.dll", EntryPoint = "GetKeyState", CharSet = CharSet.Auto)]
65        internal static extern short GetKeyState(int nVirtKey);
66
67        [DllImport("User32.dll", EntryPoint = "SendMessage", CharSet = CharSet.Auto)]
68        internal static extern IntPtr SendMessage(IntPtr hWnd, int msg, IntPtr wParam,

IntPtr lParam);
69    }
70}

安装钩子

       使用SetWindowsHookEx函数(API函数),指定一个Hook类型、自己的Hook过程是全局还是局部Hook,同时给出Hook过程的进入点,就可以轻松的安装自己的Hook过程。SetWindowsHookEx总是将你的Hook函数放置在Hook链的顶端。你可以使用CallNextHookEx函数将系统消息传递给Hook链中的下一个函数。

 

      对于某些类型的Hook,系统将向该类的所有Hook函数发送消息,这时,Hook函数中的CallNextHookEx语句将被忽略。全局(远程钩子)Hook函数可以拦截系统中所有线程的某个特定的消息,为了安装一个全局Hook过程,必须在应用程序外建立一个DLL并将该Hook函数封装到其中, 应用程序在安装全局Hook过程时必须先得到该DLL模块的句柄。将Dll名传递给LoadLibrary 函数,就会得到该DLL模块的句柄;得到该句柄 后,使用GetProcAddress函数可以得到Hook过程的地址。最后,使用SetWindowsHookEx将 Hook过程的首址嵌入相应的Hook链中,SetWindowsHookEx传递一个模块句柄,它为Hook过程的进入点,线程标识符置为0,该Hook过程同系统中的所有线程关联。如果是安装局部Hook此时该Hook函数可以放置在DLL中,也可以放置在应用程序的模块段。在C#中通过平台调用(前文已经介绍过)来调用API函数。

1    public void Start(bool installMouseHook, bool installKeyboardHook) {
2        if (hMouseHook == IntPtr.Zero && installMouseHook) {
3            MouseHookProcedure = new HookProc(MouseHookProc);
4            hMouseHook = SetWindowsHookEx(
5                WH_MOUSE_LL,
6                MouseHookProcedure,
7                Marshal.GetHINSTANCE(
8                Assembly.GetExecutingAssembly().GetModules()[0]),
9                0
10           );
11
12            if (hMouseHook == IntPtr.Zero) {
13                int errorCode = Marshal.GetLastWin32Error();
14                Stop(true, false, false);
15
16                throw new Win32Exception(errorCode);
17            }
18        }
19
20        if (hKeyboardHook == IntPtr.Zero && installKeyboardHook) {
21            KeyboardHookProcedure = new HookProc(KeyboardHookProc);
22            //install hook
23            hKeyboardHook = SetWindowsHookEx(
24                WH_KEYBOARD_LL,
25                KeyboardHookProcedure,
26                Marshal.GetHINSTANCE(
27                Assembly.GetExecutingAssembly().GetModules()[0]),
28                0);
29            // If SetWindowsHookEx fails.
30            if (hKeyboardHook == IntPtr.Zero) {
31                // Returns the error code returned by the last
32                // unmanaged function called using platform invoke
33                // that has the DllImportAttribute.SetLastError flag set.
34                int errorCode = Marshal.GetLastWin32Error();
35                //do cleanup
36                Stop(false, true, false);
37                //Initializes and throws a new instance of the
38                // Win32Exception class with the specified error.
39                throw new Win32Exception(errorCode);
40            }
41        }
42    }


使用完钩子后,要进行卸载,这个可以写在析构函数中。

1
2    public void Stop() {
3        this.Stop(true, true, true);
4    }
5   
6    public void Stop(bool uninstallMouseHook, bool uninstallKeyboardHook,
7        bool throwExceptions) {
8        // if mouse hook set and must be uninstalled
9        if (hMouseHook != IntPtr.Zero && uninstallMouseHook) {
10            // uninstall hook
11            bool retMouse = UnhookWindowsHookEx(hMouseHook);
12            // reset invalid handle
13            hMouseHook = IntPtr.Zero;
14            // if failed and exception must be thrown
15            if (retMouse == false && throwExceptions) {
16                // Returns the error code returned by the last unmanaged function
17                // called using platform invoke that has the DllImportAttribute.
18                // SetLastError flag set.
19                int errorCode = Marshal.GetLastWin32Error();
20                // Initializes and throws a new instance of the Win32Exception class
21                // with the specified error.
22                throw new Win32Exception(errorCode);
23            }
24        }
25
26        // if keyboard hook set and must be uninstalled
27        if (hKeyboardHook != IntPtr.Zero && uninstallKeyboardHook) {
28            // uninstall hook
29            bool retKeyboard = UnhookWindowsHookEx(hKeyboardHook);
30            // reset invalid handle
31            hKeyboardHook = IntPtr.Zero;
32            // if failed and exception must be thrown
33            if (retKeyboard == false && throwExceptions) {
34                // Returns the error code returned by the last unmanaged function
35                // called using platform invoke that has the DllImportAttribute.
36                // SetLastError flag set.
37                int errorCode = Marshal.GetLastWin32Error();
38                // Initializes and throws a new instance of the Win32Exception class
39                // with the specified error.
40                throw new Win32Exception(errorCode);
41            }
42        }
43    }
44


将这个文件编译成一个dll,即可在应用程序中调用。通过它提供的事件,便可监听所有的键盘事件。
但是,这只能监听键盘事件,没有键盘的情况下,怎么会有键盘事件?其实很简单,通过SendInput
API函数提供虚拟键盘代码的调用即可模拟键盘输入。下面的代码模拟一个 KeyDown 和 KeyUp 过程,
把他们连接起来就是一次按键过程。

1    private void SendKeyDown(short key) {
2        Input[] input = new Input[1];
3        input[0].type = INPUT.KEYBOARD;
4        input[0].ki.wVk = key;
5        input[0].ki.time = NativeMethods.GetTickCount();
6
7        if (NativeMethods.SendInput((uint)input.Length, input, Marshal.SizeOf(input[0]))
8            < input.Length) {
9            throw new Win32Exception(Marshal.GetLastWin32Error());
10        }
11    }
12
13    private void SendKeyUp(short key) {
14        Input[] input = new Input[1];
15        input[0].type = INPUT.KEYBOARD;
16        input[0].ki.wVk = key;
17        input[0].ki.dwFlags = KeyboardConstaint.KEYEVENTF_KEYUP;
18        input[0].ki.time = NativeMethods.GetTickCount();
19
20        if (NativeMethods.SendInput((uint)input.Length, input, Marshal.SizeOf(input[0]))
21            < input.Length) {
22            throw new Win32Exception(Marshal.GetLastWin32Error());
23        }
24    }

 

      自己实现一个 KeyBoardButton 控件用作按钮,用 Visual Studio 或者 SharpDevelop 为屏幕键盘设计 UI,然后
在这些 Button 的 Click 事件里面模拟一个按键过程。

1
2    private void ButtonOnClick(object sender, EventArgs e) {
3        KeyboardButton btnKey = sender as KeyboardButton;
4        if (btnKey == null) {
5            return;
6        }
7
8        SendKeyCommand(btnKey);
9    }
10   
11    private void SendKeyCommand(KeyboardButton keyButton) {
12        short key = keyButton.VKCode;
13        if (combinationVKButtonsMap.ContainsKey(key)) {
14            if (keyButton.Checked) {
15                SendKeyUp(key);
16            } else {
17                SendKeyDown(key);
18            }
19        } else {
20            SendKeyDown(key);
21            SendKeyUp(key);
22        }
23    }

其中 combinationVKButtonsMap 是一个 IDictionary>, key 存储的是VK_SHIFT, VK_CONTROL 等组合键的键盘码。左右两个按钮对应同一个键盘码,因此需要放在一个 List 里。
标准键盘上的每一个键都有虚拟键码( VK_CODE)与之对应。还有一些其他的常量,
把它写在一个静态 class 里吧。

1    // KeyboardConstaint.cs
2    internal static class KeyboardConstaint {
3        internal static readonly short VK_F1 = 0x70;
4        internal static readonly short VK_F2 = 0x71;
5        internal static readonly short VK_F3 = 0x72;
6        internal static readonly short VK_F4 = 0x73;
7        internal static readonly short VK_F5 = 0x74;
8        internal static readonly short VK_F6 = 0x75;
9        internal static readonly short VK_F7 = 0x76;
10        internal static readonly short VK_F8 = 0x77;
11        internal static readonly short VK_F9 = 0x78;
12        internal static readonly short VK_F10 = 0x79;
13        internal static readonly short VK_F11 = 0x7A;
14        internal static readonly short VK_F12 = 0x7B;
15
16        internal static readonly short VK_LEFT = 0x25;
17        internal static readonly short VK_UP = 0x26;
18        internal static readonly short VK_RIGHT = 0x27;
19        internal static readonly short VK_DOWN = 0x28;
20
21        internal static readonly short VK_NONE = 0x00;
22        internal static readonly short VK_ESCAPE = 0x1B;
23        internal static readonly short VK_EXECUTE = 0x2B;
24        internal static readonly short VK_CANCEL = 0x03;
25        internal static readonly short VK_RETURN = 0x0D;
26        internal static readonly short VK_ACCEPT = 0x1E;
27        internal static readonly short VK_BACK = 0x08;
28        internal static readonly short VK_TAB = 0x09;
29        internal static readonly short VK_DELETE = 0x2E;
30        internal static readonly short VK_CAPITAL = 0x14;
31        internal static readonly short VK_NUMLOCK = 0x90;
32        internal static readonly short VK_SPACE = 0x20;
33        internal static readonly short VK_DECIMAL = 0x6E;
34        internal static readonly short VK_SUBTRACT = 0x6D;
35
36        internal static readonly short VK_ADD = 0x6B;
37        internal static readonly short VK_DIVIDE = 0x6F;
38        internal static readonly short VK_MULTIPLY = 0x6A;
39        internal static readonly short VK_INSERT = 0x2D;
40
41        internal static readonly short VK_OEM_1 = 0xBA;  // ';:' for US
42        internal static readonly short VK_OEM_PLUS = 0xBB;  // '+' any country
43
44        internal static readonly short VK_OEM_MINUS = 0xBD;  // '-' any country
45
46        internal static readonly short VK_OEM_2 = 0xBF;  // '/?' for US
47        internal static readonly short VK_OEM_3 = 0xC0;  // '`~' for US
48        internal static readonly short VK_OEM_4 = 0xDB;  //  '[{' for US
49        internal static readonly short VK_OEM_5 = 0xDC;  //  '\|' for US
50        internal static readonly short VK_OEM_6 = 0xDD;  //  ']}' for US
51        internal static readonly short VK_OEM_7 = 0xDE;  //  ''"' for US
52        internal static readonly short VK_OEM_PERIOD = 0xBE;  // '.>' any country
53        internal static readonly short VK_OEM_COMMA = 0xBC;  // ',<' any country
54        internal static readonly short VK_SHIFT = 0x10;
55        internal static readonly short VK_CONTROL = 0x11;
56        internal static readonly short VK_MENU = 0x12;
57        internal static readonly short VK_LWIN = 0x5B;
58        internal static readonly short VK_RWIN = 0x5C;
59        internal static readonly short VK_APPS = 0x5D;
60
61        internal static readonly short VK_LSHIFT = 0xA0;
62        internal static readonly short VK_RSHIFT = 0xA1;
63        internal static readonly short VK_LCONTROL = 0xA2;
64        internal static readonly short VK_RCONTROL = 0xA3;
65        internal static readonly short VK_LMENU = 0xA4;
66        internal static readonly short VK_RMENU = 0xA5;
67
68        internal static readonly short VK_SNAPSHOT = 0x2C;
69        internal static readonly short VK_SCROLL = 0x91;
70        internal static readonly short VK_PAUSE = 0x13;
71        internal static readonly short VK_HOME = 0x24;
72
73        internal static readonly short VK_NEXT = 0x22;
74        internal static readonly short VK_PRIOR = 0x21;
75        internal static readonly short VK_END = 0x23;
76
77        internal static readonly short VK_NUMPAD0 = 0x60;
78        internal static readonly short VK_NUMPAD1 = 0x61;
79        internal static readonly short VK_NUMPAD2 = 0x62;
80        internal static readonly short VK_NUMPAD3 = 0x63;
81        internal static readonly short VK_NUMPAD4 = 0x64;
82        internal static readonly short VK_NUMPAD5 = 0x65;
83        internal static readonly short VK_NUMPAD5NOTHING = 0x0C;
84        internal static readonly short VK_NUMPAD6 = 0x66;
85        internal static readonly short VK_NUMPAD7 = 0x67;
86        internal static readonly short VK_NUMPAD8 = 0x68;
87        internal static readonly short VK_NUMPAD9 = 0x69;
88
89        internal static readonly short KEYEVENTF_EXTENDEDKEY    = 0x0001;
90        internal static readonly short KEYEVENTF_KEYUP          = 0x0002;
91
92        internal static readonly int GWL_EXSTYLE    = -20;
93        internal static readonly int WS_DISABLED    = 0X8000000;
94        internal static readonly int WM_SETFOCUS    = 0X0007;
95    }

屏幕键盘必须是一个不能获得输入焦点的窗体,在这个窗体的构造函数里,可以安装
一个全局鼠标钩子,再通过调用 SetWindowLong API 函数完成。

1UserActivityHook hook = new UserActivityHook(true, true);
2hook.MouseActivity += HookOnMouseActivity;
3
4private void HookOnMouseActivity(object sener, HookEx.MouseExEventArgs e) {
5    Point location = e.Location;
6
7    if (e.Button == MouseButtons.Left) {
8        Rectangle captionRect = new Rectangle(this.Location, new Size(this.Width,
9            SystemInformation.CaptionHeight));
10        if (captionRect.Contains(location)) {
11            NativeMethods.SetWindowLong(this.Handle, KeyboardConstaint.GWL_EXSTYLE,
12                (int)NativeMethods.GetWindowLong(this.Handle, KeyboardConstaint.GWL_EXSTYLE)
13                 & (~KeyboardConstaint.WS_DISABLED));
14            NativeMethods.SendMessage(this.Handle, KeyboardConstaint.WM_SETFOCUS, IntPtr.Zero,

IntPtr.Zero);
15        } else {
16            NativeMethods.SetWindowLong(this.Handle, KeyboardConstaint.GWL_EXSTYLE,
17                (int)NativeMethods.GetWindowLong(this.Handle, KeyboardConstaint.GWL_EXSTYLE) |
18                 KeyboardConstaint.WS_DISABLED);
19        }
20    }
21}

  鼠标单击标题栏,让屏幕键盘可以接收焦点,并激活,单击其他部分则不激活窗体(如果激活了,其他程序必然取消激活,输入就无法进行了),这样才可以进行输入,并且保证了可以拖动窗体到其他位置。
 
  至此,一个屏幕键盘程序差不多完成了,能够实现与实际键盘完全同步。至于窗体,按键重绘,以及 Num Lock, Caps Lock,Scroll Lock 等键盘灯的模拟,这里就不讲了,如果有兴趣,可以下载完整的代码。
 
  说明:本程序参考了 Jeffrey Richter 先生的著作 CLR via C#, Second Edition, MSDN 以及一些网络资料。
 
  这是微软技术的一贯特点,使用简单。但是如果要深入的话,还是要投入不少精力的

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