用钩子(hook)实现C#的屏幕键盘效果
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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。
- // NativeMethods.cs
- using System;
- using System.Runtime.InteropServices;
- using System.Drawing;
- namespace CnBlogs.Youzai.ScreenKeyboard
- {
- [StructLayout(LayoutKind.Sequential)]
- internal struct MOUSEINPUT
- {
- public int dx;
- public int dy;
- public int mouseData;
- public int dwFlags;
- public int time;
- public IntPtr dwExtraInfo;
- }
- [StructLayout(LayoutKind.Sequential)]
- internal struct KEYBDINPUT
- {
- public short wVk;
- public short wScan;
- public int dwFlags;
- public int time;
- public IntPtr dwExtraInfo;
- }
- [StructLayout(LayoutKind.Explicit)]
- internal struct Input
- {
- [FieldOffset(0)]
- public int type;
- [FieldOffset(4)]
- public MOUSEINPUT mi;
- [FieldOffset(4)]
- public KEYBDINPUT ki;
- [FieldOffset(4)]
- public HARDWAREINPUT hi;
- }
- [StructLayout(LayoutKind.Sequential)]
- internal struct HARDWAREINPUT
- {
- public int uMsg;
- public short wParamL;
- public short wParamH;
- }
- internal class INPUT
- {
- public const int MOUSE = 0;
- public const int KEYBOARD = 1;
- public const int HARDWARE = 2;
- }
- internal static class NativeMethods
- {
- [DllImport("User32.dll", CharSet = CharSet.Auto, SetLastError = false)]
- internal static extern IntPtr GetWindowLong(IntPtr hWnd, int nIndex);
- [DllImport("User32.dll", CharSet = CharSet.Auto, SetLastError = false)]
- internal static extern IntPtr SetWindowLong(IntPtr hWnd, int nIndex, int dwNewLong);
- [DllImport("User32.dll", EntryPoint = "SendInput", CharSet = CharSet.Auto)]
- internal static extern UInt32 SendInput(UInt32 nInputs, Input[] pInputs, Int32 cbSize);
- [DllImport("Kernel32.dll", EntryPoint = "GetTickCount", CharSet = CharSet.Auto)]
- internal static extern int GetTickCount();
- [DllImport("User32.dll", EntryPoint = "GetKeyState", CharSet = CharSet.Auto)]
- internal static extern short GetKeyState(int nVirtKey);
- [DllImport("User32.dll", EntryPoint = "SendMessage", CharSet = CharSet.Auto)]
- internal static extern IntPtr SendMessage(IntPtr hWnd, int msg, IntPtr wParam, IntPtr lParam);
- }
- }
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。
- public void Start(bool installMouseHook, bool installKeyboardHook)
- {
- if (hMouseHook == IntPtr.Zero && installMouseHook)
- {
- MouseHookProcedure = new HookProc(MouseHookProc);
- hMouseHook = SetWindowsHookEx(
- WH_MOUSE_LL,
- MouseHookProcedure,
- Marshal.GetHINSTANCE(Assembly.GetExecutingAssembly().GetModules()[0]), 0);
- if (hMouseHook == IntPtr.Zero)
- {
- int errorCode = Marshal.GetLastWin32Error();
- Stop(true, false, false);
- throw new Win32Exception(errorCode);
- }
- }
- if (hKeyboardHook == IntPtr.Zero && installKeyboardHook)
- {
- KeyboardHookProcedure = new HookProc(KeyboardHookProc);
- //install hook
- hKeyboardHook = SetWindowsHookEx(
- WH_KEYBOARD_LL,
- KeyboardHookProcedure,
- Marshal.GetHINSTANCE(
- Assembly.GetExecutingAssembly().GetModules()[0]),
- 0);
- // If SetWindowsHookEx fails.
- if (hKeyboardHook == IntPtr.Zero)
- {
- // Returns the error code returned by the last
- // unmanaged function called using platform invoke
- // that has the DllImportAttribute.SetLastError flag set.
- int errorCode = Marshal.GetLastWin32Error();
- //do cleanup
- Stop(false, true, false);
- //Initializes and throws a new instance of the
- // Win32Exception class with the specified error.
- throw new Win32Exception(errorCode);
- }
- }
- }
使用完钩子后,要进行卸载,这个可以写在析构函数中。
- public void Stop()
- {
- this.Stop(true, true, true);
- }
- public void Stop(bool uninstallMouseHook, bool uninstallKeyboardHook,
- bool throwExceptions)
- {
- // if mouse hook set and must be uninstalled
- if (hMouseHook != IntPtr.Zero && uninstallMouseHook)
- {
- // uninstall hook
- bool retMouse = UnhookWindowsHookEx(hMouseHook);
- // reset invalid handle
- hMouseHook = IntPtr.Zero;
- // if failed and exception must be thrown
- if (retMouse == false && throwExceptions)
- {
- // Returns the error code returned by the last unmanaged function
- // called using platform invoke that has the DllImportAttribute.
- // SetLastError flag set.
- int errorCode = Marshal.GetLastWin32Error();
- // Initializes and throws a new instance of the Win32Exception class
- // with the specified error.
- throw new Win32Exception(errorCode);
- }
- }
- // if keyboard hook set and must be uninstalled
- if (hKeyboardHook != IntPtr.Zero && uninstallKeyboardHook)
- {
- // uninstall hook
- bool retKeyboard = UnhookWindowsHookEx(hKeyboardHook);
- // reset invalid handle
- hKeyboardHook = IntPtr.Zero;
- // if failed and exception must be thrown
- if (retKeyboard == false && throwExceptions)
- {
- // Returns the error code returned by the last unmanaged function
- // called using platform invoke that has the DllImportAttribute.
- // SetLastError flag set.
- int errorCode = Marshal.GetLastWin32Error();
- // Initializes and throws a new instance of the Win32Exception class
- // with the specified error.
- throw new Win32Exception(errorCode);
- }
- }
- }
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。
- private void SendKeyDown(short key)
- {
- Input[] input = new Input[1];
- input[0].type = INPUT.KEYBOARD;
- input[0].ki.wVk = key;
- input[0].ki.time = NativeMethods.GetTickCount();
- if (NativeMethods.SendInput((uint)input.Length, input, Marshal.SizeOf(input[0])) < input.Length)
- {
- throw new Win32Exception(Marshal.GetLastWin32Error());
- }
- }
- private void SendKeyUp(short key)
- {
- Input[] input = new Input[1];
- input[0].type = INPUT.KEYBOARD;
- input[0].ki.wVk = key;
- input[0].ki.dwFlags = KeyboardConstaint.KEYEVENTF_KEYUP;
- input[0].ki.time = NativeMethods.GetTickCount();
- if (NativeMethods.SendInput((uint)input.Length, input, Marshal.SizeOf(input[0])) < input.Length)
- {
- throw new Win32Exception(Marshal.GetLastWin32Error());
- }
- }
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。
- private void ButtonOnClick(object sender, EventArgs e)
- {
- KeyboardButton btnKey = sender as KeyboardButton;
- if (btnKey == null)
- {
- return;
- }
- SendKeyCommand(btnKey);
- }
- private void SendKeyCommand(KeyboardButton keyButton)
- {
- short key = keyButton.VKCode;
- if (combinationVKButtonsMap.ContainsKey(key))
- {
- if (keyButton.Checked)
- {
- SendKeyUp(key);
- }
- else
- {
- SendKeyDown(key);
- }
- }
- else
- {
- SendKeyDown(key);
- SendKeyUp(key);
- }
- }
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。
- // KeyboardConstaint.cs
- internal static class KeyboardConstaint
- {
- internal static readonly short VK_F1 = 0x70;
- internal static readonly short VK_F2 = 0x71;
- internal static readonly short VK_F3 = 0x72;
- internal static readonly short VK_F4 = 0x73;
- internal static readonly short VK_F5 = 0x74;
- internal static readonly short VK_F6 = 0x75;
- internal static readonly short VK_F7 = 0x76;
- internal static readonly short VK_F8 = 0x77;
- internal static readonly short VK_F9 = 0x78;
- internal static readonly short VK_F10 = 0x79;
- internal static readonly short VK_F11 = 0x7A;
- internal static readonly short VK_F12 = 0x7B;
- internal static readonly short VK_LEFT = 0x25;
- internal static readonly short VK_UP = 0x26;
- internal static readonly short VK_RIGHT = 0x27;
- internal static readonly short VK_DOWN = 0x28;
- internal static readonly short VK_NONE = 0x00;
- internal static readonly short VK_ESCAPE = 0x1B;
- internal static readonly short VK_EXECUTE = 0x2B;
- internal static readonly short VK_CANCEL = 0x03;
- internal static readonly short VK_RETURN = 0x0D;
- internal static readonly short VK_ACCEPT = 0x1E;
- internal static readonly short VK_BACK = 0x08;
- internal static readonly short VK_TAB = 0x09;
- internal static readonly short VK_DELETE = 0x2E;
- internal static readonly short VK_CAPITAL = 0x14;
- internal static readonly short VK_NUMLOCK = 0x90;
- internal static readonly short VK_SPACE = 0x20;
- internal static readonly short VK_DECIMAL = 0x6E;
- internal static readonly short VK_SUBTRACT = 0x6D;
- internal static readonly short VK_ADD = 0x6B;
- internal static readonly short VK_DIVIDE = 0x6F;
- internal static readonly short VK_MULTIPLY = 0x6A;
- internal static readonly short VK_INSERT = 0x2D;
- internal static readonly short VK_OEM_1 = 0xBA; // ';:' for US
- internal static readonly short VK_OEM_PLUS = 0xBB; // '+' any country
- internal static readonly short VK_OEM_MINUS = 0xBD; // '-' any country
- internal static readonly short VK_OEM_2 = 0xBF; // '/?' for US
- internal static readonly short VK_OEM_3 = 0xC0; // '`~' for US
- internal static readonly short VK_OEM_4 = 0xDB; // '[{' for US
- internal static readonly short VK_OEM_5 = 0xDC; // '/|' for US
- internal static readonly short VK_OEM_6 = 0xDD; // ']}' for US
- internal static readonly short VK_OEM_7 = 0xDE; // ''"' for US
- internal static readonly short VK_OEM_PERIOD = 0xBE; // '.>' any country
- internal static readonly short VK_OEM_COMMA = 0xBC; // ',<' any country
- internal static readonly short VK_SHIFT = 0x10;
- internal static readonly short VK_CONTROL = 0x11;
- internal static readonly short VK_MENU = 0x12;
- internal static readonly short VK_LWIN = 0x5B;
- internal static readonly short VK_RWIN = 0x5C;
- internal static readonly short VK_APPS = 0x5D;
- internal static readonly short VK_LSHIFT = 0xA0;
- internal static readonly short VK_RSHIFT = 0xA1;
- internal static readonly short VK_LCONTROL = 0xA2;
- internal static readonly short VK_RCONTROL = 0xA3;
- internal static readonly short VK_LMENU = 0xA4;
- internal static readonly short VK_RMENU = 0xA5;
- internal static readonly short VK_SNAPSHOT = 0x2C;
- internal static readonly short VK_SCROLL = 0x91;
- internal static readonly short VK_PAUSE = 0x13;
- internal static readonly short VK_HOME = 0x24;
- internal static readonly short VK_NEXT = 0x22;
- internal static readonly short VK_PRIOR = 0x21;
- internal static readonly short VK_END = 0x23;
- internal static readonly short VK_NUMPAD0 = 0x60;
- internal static readonly short VK_NUMPAD1 = 0x61;
- internal static readonly short VK_NUMPAD2 = 0x62;
- internal static readonly short VK_NUMPAD3 = 0x63;
- internal static readonly short VK_NUMPAD4 = 0x64;
- internal static readonly short VK_NUMPAD5 = 0x65;
- internal static readonly short VK_NUMPAD5NOTHING = 0x0C;
- internal static readonly short VK_NUMPAD6 = 0x66;
- internal static readonly short VK_NUMPAD7 = 0x67;
- internal static readonly short VK_NUMPAD8 = 0x68;
- internal static readonly short VK_NUMPAD9 = 0x69;
- internal static readonly short KEYEVENTF_EXTENDEDKEY = 0x0001;
- internal static readonly short KEYEVENTF_KEYUP = 0x0002;
- internal static readonly int GWL_EXSTYLE = -20;
- internal static readonly int WS_DISABLED = 0X8000000;
- internal static readonly int WM_SETFOCUS = 0X0007;
- }
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。
- UserActivityHook hook = new UserActivityHook(true, true);
- hook.MouseActivity += HookOnMouseActivity;
- private void HookOnMouseActivity(object sener, HookEx.MouseExEventArgs e)
- {
- Point location = e.Location;
- if (e.Button == MouseButtons.Left)
- {
- Rectangle captionRect = new Rectangle(this.Location, new Size(this.Width, SystemInformation.CaptionHeight));
- if (captionRect.Contains(location))
- {
- NativeMethods.SetWindowLong(this.Handle, KeyboardConstaint.GWL_EXSTYLE, (int)NativeMethods.GetWindowLong(this.Handle, KeyboardConstaint.GWL_EXSTYLE) & (~KeyboardConstaint.WS_DISABLED));
- NativeMethods.SendMessage(this.Handle, KeyboardConstaint.WM_SETFOCUS, IntPtr.Zero, IntPtr.Zero);
- }
- else
- {
- NativeMethods.SetWindowLong(this.Handle, KeyboardConstaint.GWL_EXSTYLE, (int)NativeMethods.GetWindowLong(this.Handle, KeyboardConstaint.GWL_EXSTYLE) | KeyboardConstaint.WS_DISABLED);
- }
- }
- }
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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