C# 實現螢幕鍵盤 (ScreenKeyboard)

要實現一個螢幕鍵盤，需要監聽所有鍵盤事件，無論窗體是否被啟用。因此需要一個全域性的鉤子，也就
是系統範圍的鉤子。

什麼是鉤子（Hook）

鉤子（Hook）是Windows提供的一種訊息處理機制平臺，是指在程式正常執行中接受資訊之前預先
啟動的函式，用來檢查和修改傳給該程式的資訊，（鉤子）實際上是一個處理訊息的程式段，通
過系統呼叫，把它掛入系統。每當特定的訊息發出，在沒有到達目的視窗前，鉤子程式就先捕獲
該訊息，亦即鉤子函式先得到控制權。這時鉤子函式即可以加工處理（改變）該訊息，也可以不
作處理而繼續傳遞該訊息，還可以強制結束訊息的傳遞。注意：安裝鉤子函式將會影響系統的性
能。監測“系統範圍事件”的系統鉤子特別明顯。因為系統在處理所有的相關事件時都將呼叫您的
鉤子函式，這樣您的系統將會明顯的減慢。所以應謹慎使用，用完後立即解除安裝。還有，由於您可
以預先截獲其它程式的訊息，所以一旦您的鉤子函式出了問題的話必將影響其它的程式。

鉤子的作用範圍
一共有兩種範圍（型別）的鉤子，區域性的和遠端的。區域性鉤子僅鉤掛自己程式的事件。遠端的鉤
子還可以將鉤掛其它程式發生的事件。遠端的鉤子又有兩種：基於執行緒的鉤子將捕獲其它程式中
某一特定執行緒的事件。簡言之，就是可以用來觀察其它程式中的某一特定執行緒將發生的事件。系
統範圍的鉤子將捕捉系統中所有程式將發生的事件訊息。

Hook 型別
Windows共有14種Hooks，每一種型別的Hook可以使應用程式能夠監視不同型別的系統訊息處理機
制。下面描述所有可以利用的Hook型別的發生時機。詳細內容可以查閱MSDN，這裡只介紹我們將要
用到的兩種型別的鉤子。

（1）WH_KEYBOARD_LL Hook
      WH_KEYBOARD_LL Hook監視輸入到執行緒訊息佇列中的鍵盤訊息。

（2）WH_MOUSE_LL Hook
      WH_MOUSE_LL Hook監視輸入到執行緒訊息佇列中的滑鼠訊息。

下面的 class 把 API 呼叫封裝起來以便呼叫。
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}

安裝鉤子
使用SetWindowsHookEx函式（API函式），指定一個Hook型別、自己的Hook過程是全域性還是區域性Hook，
同時給出Hook過程的進入點，就可以輕鬆的安裝自己的Hook過程。SetWindowsHookEx總是將你的Hook函
數放置在Hook鏈的頂端。你可以使用CallNextHookEx函式將系統訊息傳遞給Hook鏈中的下一個函式。
對於某些型別的Hook，系統將向該類的所有Hook函式傳送訊息，這時，
Hook函式中的CallNextHookEx語句將被忽略。全域性（遠端鉤子）Hook函式可以攔截系統中所有執行緒的某
個特定的訊息，為了安裝一個全域性Hook過程，必須在應用程式外建立一個DLL並將該Hook函式封裝到其中，
應用程式在安裝全域性Hook過程時必須先得到該DLL模組的控制程式碼。將Dll名傳遞給LoadLibrary 函式，就會得
到該DLL模組的控制程式碼；得到該控制程式碼後，使用GetProcAddress函式可以得到Hook過程的地址。最後，使用
SetWindowsHookEx將 Hook過程的首址嵌入相應的Hook鏈中，SetWindowsHookEx傳遞一個模組控制程式碼，它為
Hook過程的進入點，執行緒識別符號置為0，該Hook過程同系統中的所有執行緒關聯。如果是安裝區域性Hook此時
該Hook函式可以放置在DLL中，也可以放置在應用程式的模組段。在C#中通過平臺呼叫（前文已經介紹過）
來呼叫API函式。
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 }

使用完鉤子後，要進行解除安裝，這個可以寫在解構函式中。
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

將這個檔案編譯成一個dll，即可在應用程式中呼叫。通過它提供的事件，便可監聽所有的鍵盤事件。
但是，這隻能監聽鍵盤事件，沒有鍵盤的情況下，怎麼會有鍵盤事件？其實很簡單，通過SendInput
API函式提供虛擬鍵盤程式碼的呼叫即可模擬鍵盤輸入。下面的程式碼模擬一個 KeyDown 和 KeyUp 過程，
把他們連線起來就是一次按鍵過程。
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 }

自己實現一個 KeyBoardButton 控制元件用作按鈕，用 Visual Studio 或者 SharpDevelop 為螢幕鍵盤設計 UI，然後
在這些 Button 的 Click 事件裡面模擬一個按鍵過程。
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 是一個 IDictionary>, key 儲存的是
VK_SHIFT, VK_CONTROL 等組合鍵的鍵盤碼。左右兩個按鈕對應同一個鍵盤碼，因此需要放在一個 List 裡。
標準鍵盤上的每一個鍵都有虛擬鍵碼( VK_CODE)與之對應。還有一些其他的常量，
把它寫在一個靜態 class 裡吧。
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;  // ', 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 }

螢幕鍵盤必須是一個不能獲得輸入焦點的窗體，在這個窗體的建構函式裡，可以安裝
一個全域性滑鼠鉤子，再通過呼叫 SetWindowLong API 函式完成。
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}

滑鼠單擊標題欄，讓螢幕鍵盤可以接收焦點，並啟用，單擊其他部分則不啟用窗體（如果啟用了，其他程式必然取消啟用，
輸入就無法進行了），這樣才可以進行輸入，並且保證了可以拖動窗體到其他位置。

至此，一個螢幕鍵盤程式差不多完成了，能夠實現與實際鍵盤完全同步。至於窗體，按鍵重繪，以及 Num Lock, Caps Lock,
Scroll Lock 等鍵盤燈的模擬，這裡就不講了，如果有興趣，可以下載完整的程式碼。最後我們的螢幕鍵盤程式執行的效果如
下圖:

C# 實現螢幕鍵盤 (ScreenKeyboard)

ScreenKeyboard.PNG

來自 “ ITPUB部落格 ” ，連結：http://blog.itpub.net/12921506/viewspace-277852/，如需轉載，請註明出處，否則將追究法律責任。

C# 實現螢幕鍵盤 (ScreenKeyboard)

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