C# 實現螢幕鍵盤 ScreenKeyboard（二）——SetWindowsHookEx 安裝全域鉤子完整實現

鉤子類型與範圍

• 局部鉤子：僅攔截本進程執行緒事件
• 遠端鉤子 (全域)：攔截所有進程事件，需 DLL 封裝
• 執行緒鉤子：針對特定執行緒

全域鉤子安裝必要條件

1. 鉤子程序放在 DLL 中
2. LoadLibrary 取得 DLL 模組控制代碼
3. GetProcAddress 取得鉤子程序位址
4. SetWindowsHookEx 傳入模組控制代碼、執行緒 ID=0 (關聯所有執行緒)

C# 平台呼叫實現

public void Start(bool installMouseHook, bool installKeyboardHook)
{
    // 滑鼠鉤子 (WH_MOUSE_LL = 14)
    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);
        }
    }

    // 鍵盤鉤子 (WH_KEYBOARD_LL = 13)
    if (hKeyboardHook == IntPtr.Zero && installKeyboardHook)
    {
        KeyboardHookProcedure = new HookProc(KeyboardHookProc);
        hKeyboardHook = SetWindowsHookEx(
            WH_KEYBOARD_LL,
            KeyboardHookProcedure,
            Marshal.GetHINSTANCE(Assembly.GetExecutingAssembly().GetModules()[0]),
            0);
        
        if (hKeyboardHook == IntPtr.Zero)
        {
            int errorCode = Marshal.GetLastWin32Error();
            Stop(false, true, false);
            throw new Win32Exception(errorCode);
        }
    }
}

關鍵技術細節

• WH_MOUSE_LL / WH_KEYBOARD_LL：低階鉤子，不需 DLL 分離，C# 直接安裝全域鉤子
• Marshal.GetHINSTANCE：取得當前組件模組控制代碼，替代 LoadLibrary
• Assembly.GetExecutingAssembly().GetModules()[0]：取得主模組
• 執行緒 ID = 0：關聯所有桌面執行緒 (全域)
• 委派持有：MouseHookProcedure、KeyboardHookProcedure 必須為成員變數，防止 GC 回收
• 失敗回滾：安裝失敗時呼叫 Stop 清理已安裝鉤子