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
（）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
（）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
// NativeMethodscs
using System;
using SystemRuntimeInteropServices;
using SystemDrawing;
namespace CnBlogsYouzaiScreenKeyboard {
[StructLayout(LayoutKindSequential)]
internal struct MOUSEINPUT {
public int dx;
public int dy;
public int mouseData;
public int dwFlags;
public int time;
public IntPtr dwExtraInfo;
}
[StructLayout(LayoutKindSequential)]
internal struct KEYBDINPUT {
public short wVk;
public short wScan;
public int dwFlags;
public int time;
public IntPtr dwExtraInfo;
}
[StructLayout(LayoutKindExplicit)]
internal struct Input {
[FieldOffset()]
public int type;
[FieldOffset()]
public MOUSEINPUT mi;
[FieldOffset()]
public KEYBDINPUT ki;
[FieldOffset()]
public HARDWAREINPUT hi;
}
[StructLayout(LayoutKindSequential)]
internal struct HARDWAREINPUT {
public int uMsg;
public short wParamL;
public short wParamH;
}
internal class INPUT {
public const int MOUSE = ;
public const int KEYBOARD = ;
public const int HARDWARE = ;
}
internal static class NativeMethods {
[DllImport(Userdll CharSet = CharSetAuto SetLastError = false)]
internal static extern IntPtr GetWindowLong(IntPtr hWnd int nIndex);
[DllImport(Userdll CharSet = CharSetAuto SetLastError = false)]
internal static extern IntPtr SetWindowLong(IntPtr hWnd int nIndex int dwNewLong);
[DllImport(Userdll EntryPoint = SendInput CharSet = CharSetAuto)]
internal static extern UInt SendInput(UInt nInputs Input[] pInputs Int cbSize);
[DllImport(Kerneldll EntryPoint = GetTickCount CharSet = CharSetAuto)]
internal static extern int GetTickCount();
[DllImport(Userdll EntryPoint = GetKeyState CharSet = CharSetAuto)]
internal static extern short GetKeyState(int nVirtKey);
[DllImport(Userdll EntryPoint = SendMessage CharSet = CharSetAuto)]
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 == IntPtrZero && installMouseHook) {
MouseHookProcedure = new HookProc(MouseHookProc);
hMouseHook = SetWindowsHookEx(
WH_MOUSE_LL
MouseHookProcedure
MarshalGetHINSTANCE(
AssemblyGetExecutingAssembly()GetModules()[])
);
if (hMouseHook == IntPtrZero) {
int errorCode = MarshalGetLastWinError();
Stop(true false false);
throw new WinException(errorCode);
}
}
if (hKeyboardHook == IntPtrZero && installKeyboardHook) {
KeyboardHookProcedure = new HookProc(KeyboardHookProc);
//install hook
hKeyboardHook = SetWindowsHookEx(
WH_KEYBOARD_LL
KeyboardHookProcedure
MarshalGetHINSTANCE(
AssemblyGetExecutingAssembly()GetModules()[])
);
// If SetWindowsHookEx fails
if (hKeyboardHook == IntPtrZero) {
// Returns the error code returned by the last
// unmanaged function called using platform invoke
// that has the DllImportAttributeSetLastError flag set
int errorCode = MarshalGetLastWinError();
//do cleanup
Stop(false true false);
//Initializes and throws a new instance of the
// WinException class with the specified error
throw new WinException(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() {
thisStop(true true true);
}
public void Stop(bool uninstallMouseHook bool uninstallKeyboardHook
bool throwExceptions) {
// if mouse hook set and must be uninstalled
if (hMouseHook != IntPtrZero && uninstallMouseHook) {
// uninstall hook
bool retMouse = UnhookWindowsHookEx(hMouseHook);
// reset invalid handle
hMouseHook = IntPtrZero;
// 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 = MarshalGetLastWinError();
// Initializes and throws a new instance of the WinException class
// with the specified error
throw new WinException(errorCode);
}
}
// if keyboard hook set and must be uninstalled
if (hKeyboardHook != IntPtrZero && uninstallKeyboardHook) {
// uninstall hook
bool retKeyboard = UnhookWindowsHookEx(hKeyboardHook);
// reset invalid handle
hKeyboardHook = IntPtrZero;
// 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 = MarshalGetLastWinError();
// Initializes and throws a new instance of the WinException class
// with the specified error
throw new WinException(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[];
input[]type = INPUTKEYBOARD;
input[]kiwVk = key;
input[]kitime = NativeMethodsGetTickCount();
if (NativeMethodsSendInput((uint)inputLength input MarshalSizeOf(input[]))
< inputLength) {
throw new WinException(MarshalGetLastWinError());
}
}
private void SendKeyUp(short key) {
Input[] input = new Input[];
input[]type = INPUTKEYBOARD;
input[]kiwVk = key;
input[]kidwFlags = KeyboardConstaintKEYEVENTF_KEYUP;
input[]kitime = NativeMethodsGetTickCount();
if (NativeMethodsSendInput((uint)inputLength input MarshalSizeOf(input[]))
< inputLength) {
throw new WinException(MarshalGetLastWinError());
}
}
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 = keyButtonVKCode;
if (combinationVKButtonsMapContainsKey(key)) {
if (keyButtonChecked) {
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。TW.wINGwIT.cOm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 先生的着作 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
