目前的程序中想要添加Hook，截获键盘按键消息，所以上网找了一下关于C# Hook的东西。发现很多人都在说在添加C# Hook不成功和不稳定，而建议使用C++封一个Dll给C#使用。可喜的是最后我还是成功的在程序中使用C#添加了Hook，经过测试还是没有什么问题的。
进行Hook需要使用三个API函数
SetWindowsHookEx 进行Hook的注册
UnhookWindowsHookEx 取消已经注册的Hook
CallNextHookEx 将消息传递给下一个Hook函数
看一下定义
- [DllImport("user32.dll")]
- private static extern IntPtr SetWindowsHookEx(
- HookType code, HookProc func, IntPtr instance, int threadID);
- [DllImport("user32.dll")]
- private static extern int UnhookWindowsHookEx(IntPtr hook);
- [DllImport("user32.dll")]
- private static extern int CallNextHookEx(
- IntPtr hook, int code, IntPtr wParam, ref KBDLLHOOKSTRUCT lParam);
我们需要定义一个delegate来接收消息
- private delegate int HookProc(int code, IntPtr wParam, ref KBDLLHOOKSTRUCT lParam);
定义两个event提供给外界使用
- public delegate void HookEventHandler(object sender, HookEventArgs e);
- public event HookEventHandler KeyDown;
- public event HookEventHandler KeyUp;
因为要接收的是键盘的消息所以要定义一些消息，和我们要接收的结构。
- public class HookEventArgs : EventArgs
- {
- // using Windows.Forms.Keys instead of Input.Key since the Forms.Keys maps
- // to the Win32 KBDLLHOOKSTRUCT virtual key member, where Input.Key does not
- public Keys Key;
- public bool Alt;
- public bool Control;
- public bool Shift;
- public HookEventArgs(UInt32 keyCode)
- {
- // detect what modifier keys are pressed, using
- // Windows.Forms.Control.ModifierKeys instead of Keyboard.Modifiers
- // since Keyboard.Modifiers does not correctly get the state of the
- // modifier keys when the application does not have focus
- this.Key = (Keys)keyCode;
- this.Alt = (System.Windows.Forms.Control.ModifierKeys & Keys.Alt) != 0;
- this.Control = (System.Windows.Forms.Control.ModifierKeys & Keys.Control) != 0;
- this.Shift = (System.Windows.Forms.Control.ModifierKeys & Keys.Shift) != 0;
- }
- }
- private enum HookType : int
- {
- WH_JOURNALRECORD = 0,
- WH_JOURNALPLAYBACK = 1,
- WH_KEYBOARD = 2,
- WH_GETMESSAGE = 3,
- WH_CALLWNDPROC = 4,
- WH_CBT = 5,
- WH_SYSMSGFILTER = 6,
- WH_MOUSE = 7,
- WH_HARDWARE = 8,
- WH_DEBUG = 9,
- WH_SHELL = 10,
- WH_FOREGROUNDIDLE = 11,
- WH_CALLWNDPROCRET = 12,
- WH_KEYBOARD_LL = 13,
- WH_MOUSE_LL = 14
- }
- public struct KBDLLHOOKSTRUCT
- {
- public UInt32 vkCode;
- public UInt32 scanCode;
- public UInt32 flags;
- public UInt32 time;
- public IntPtr extraInfo;
- }
关键的在这里注册C# Hook
- private void Install()
- {
- if (_hookHandle != IntPtr.Zero)
- return;
- Module[] list = System.Reflection.Assembly.GetExecutingAssembly().GetModules();
- System.Diagnostics.Debug.Assert(list != null && list.Length > 0);
- _hookHandle = SetWindowsHookEx(_hookType,
- _hookFunction, Marshal.GetHINSTANCE(list[0]), 0);
- }
哦，还有HookType _hookType = HookType.WH_KEYBOARD_LL; 因为要截获键盘消息
还有_hookFunction = new HookProc(HookCallback);
其实最关键的是Marshal.GetHINSTANCE(list[0])得到当前程序的instance，这样这个C# Hook就是全局的C# Hook，这个位置也可以是null，这样就不是全局C# Hook。
有个很奇怪的现象就是这个函数，在调试状态执行不能成功，而做成Release以后运行成功，所以你在做程序时，不要因为调试失败而对这个函数有怀疑，编一个Release版本的程序，独立运行再试一下。我使用的环境是VS2005 + Vista。
接收消息的函数
- private int HookCallback(int code, IntPtr wParam, ref KBDLLHOOKSTRUCT lParam)
- {
- if (code < 0)
- return CallNextHookEx(_hookHandle, code, wParam, ref lParam);
- if ((lParam.flags & 0x80) != 0 && this.KeyUp != null)
- this.KeyUp(this, new HookEventArgs(lParam.vkCode));
- if ((lParam.flags & 0x80) == 0 && this.KeyDown != null)
- {
- this.KeyDown(this, new HookEventArgs(lParam.vkCode));
- if (lParam.vkCode == 44)
- {
- return 1;
- }
- }
- return CallNextHookEx(_hookHandle, code, wParam, ref lParam);
- }
这里会区分KeyUp和KeyDown，注意一定要调用CallNextHookEx，这样会将这个消息在系统中继续传递，这很重要。除非你想阻止这个消息，也不希望其他程序再处理这个消息。
下面最后的操作，释放注册。
- private void Uninstall()
- {
- if (_hookHandle != IntPtr.Zero)
- {
- UnhookWindowsHookEx(_hookHandle);
- _hookHandle = IntPtr.Zero;
- }
- }
Ok，完成了。
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