我正在使用此代码GlobalKeyboardHook.cs来钩住键盘。
我已经按照this post中的说明更改了所有指定的内容。现在，我的代码如下所示：
using System;
using System.Collections.Generic;
using System.Text;
using System.Runtime.InteropServices;
using System.Windows.Forms;
namespace Utilities
{
/// <summary>
/// A class that manages a global low level keyboard hook
/// </summary>
class globalKeyboardHook
{
#region Constant, Structure and Delegate Definitions
/// <summary>
/// defines the callback type for the hook
/// </summary>
public delegate int keyboardHookProc(int code, int wParam, ref keyboardHookStruct lParam);
public struct keyboardHookStruct
{
public int vkCode;
public int scanCode;
public int flags;
public int time;
public int dwExtraInfo;
}
const int WH_KEYBOARD_LL = 13;
const int WM_KEYDOWN = 0x100;
const int WM_KEYUP = 0x101;
const int WM_SYSKEYDOWN = 0x104;
const int WM_SYSKEYUP = 0x105;
private static keyboardHookProc callbackDelegate;
#endregion
#region Instance Variables
/// <summary>
/// The collections of keys to watch for
/// </summary>
public List<Keys> HookedKeys = new List<Keys>();
/// <summary>
/// Handle to the hook, need this to unhook and call the next hook
/// </summary>
IntPtr hhook = IntPtr.Zero;
#endregion
#region Events
/// <summary>
/// Occurs when one of the hooked keys is pressed
/// </summary>
public event KeyEventHandler KeyDown;
/// <summary>
/// Occurs when one of the hooked keys is released
/// </summary>
public event KeyEventHandler KeyUp;
#endregion
#region Constructors and Destructors
/// <summary>
/// Initializes a new instance of the <see cref="globalKeyboardHook"/> class and installs the keyboard hook.
/// </summary>
public globalKeyboardHook()
{
hook();
}
/// <summary>
/// Releases unmanaged resources and performs other cleanup operations before the
/// <see cref="globalKeyboardHook"/> is reclaimed by garbage collection and uninstalls the keyboard hook.
/// </summary>
~globalKeyboardHook()
{
unhook();
}
#endregion
#region Public Methods
/// <summary>
/// Installs the global hook
/// </summary>
public void hook()
{
IntPtr hInstance = LoadLibrary("User32");
callbackDelegate = new keyboardHookProc(hookProc);
hhook = SetWindowsHookEx(WH_KEYBOARD_LL, hookProc, hInstance, 0);
if (hhook == IntPtr.Zero) throw new System.ComponentModel.Win32Exception();
}
/// <summary>
/// Uninstalls the global hook
/// </summary>
public void unhook()
{
bool ok = UnhookWindowsHookEx(hhook);
if (!ok) throw new System.ComponentModel.Win32Exception();
callbackDelegate = null;
}
/// <summary>
/// The callback for the keyboard hook
/// </summary>
/// <param name="code">The hook code, if it isn't >= 0, the function shouldn't do anyting</param>
/// <param name="wParam">The event type</param>
/// <param name="lParam">The keyhook event information</param>
/// <returns></returns>
public int hookProc(int code, int wParam, ref keyboardHookStruct lParam)
{
if (code >= 0)
{
Keys key = (Keys)lParam.vkCode;
if (HookedKeys.Contains(key))
{
KeyEventArgs kea = new KeyEventArgs(key);
if ((wParam == WM_KEYDOWN || wParam == WM_SYSKEYDOWN) && (KeyDown != null))
{
KeyDown(this, kea);
}
else if ((wParam == WM_KEYUP || wParam == WM_SYSKEYUP) && (KeyUp != null))
{
KeyUp(this, kea);
}
if (kea.Handled)
return 1;
}
}
return CallNextHookEx(hhook, code, wParam, ref lParam);
}
#endregion
#region DLL imports
/// <summary>
/// Sets the windows hook, do the desired event, one of hInstance or threadId must be non-null
/// </summary>
/// <param name="idHook">The id of the event you want to hook</param>
/// <param name="callback">The callback.</param>
/// <param name="hInstance">The handle you want to attach the event to, can be null</param>
/// <param name="threadId">The thread you want to attach the event to, can be null</param>
/// <returns>a handle to the desired hook</returns>
[DllImport("user32.dll")]
static extern IntPtr SetWindowsHookEx(int idHook, keyboardHookProc callback, IntPtr hInstance, uint threadId);
/// <summary>
/// Unhooks the windows hook.
/// </summary>
/// <param name="hInstance">The hook handle that was returned from SetWindowsHookEx</param>
/// <returns>True if successful, false otherwise</returns>
[DllImport("user32.dll")]
static extern bool UnhookWindowsHookEx(IntPtr hInstance);
/// <summary>
/// Calls the next hook.
/// </summary>
/// <param name="idHook">The hook id</param>
/// <param name="nCode">The hook code</param>
/// <param name="wParam">The wparam.</param>
/// <param name="lParam">The lparam.</param>
/// <returns></returns>
[DllImport("user32.dll")]
static extern int CallNextHookEx(IntPtr idHook, int nCode, int wParam, ref keyboardHookStruct lParam);
/// <summary>
/// Loads the library.
/// </summary>
/// <param name="lpFileName">Name of the library</param>
/// <returns>A handle to the library</returns>
[DllImport("kernel32.dll")]
static extern IntPtr LoadLibrary(string lpFileName);
#endregion
}
}
当我的程序窗口可见时，程序中的此功能将挂钩UP和DOWN键。可见性发生变化时，它将为这些键解钩。
private void AutoCompleteMenu_VisibleChanged(object sender, EventArgs e)
{
if (this.Visible == true)
{
if (hookFlag == 0)
{
try
{
gkh.hook();
gkh.HookedKeys.Add(Keys.Up);
gkh.HookedKeys.Add(Keys.Down);
gkh.KeyDown += new KeyEventHandler(gkh_KeyDown);
gkh.KeyUp += new KeyEventHandler(gkh_KeyUp);
}
catch (Exception)
{
MessageBox.Show("Cannot hook arrow keys! Please use mouse keys to select a word");
}
hookFlag = 1;
}
}
else
{
if (hookFlag == 1)
{
hookFlag = 0;
gkh.unhook();
}
}
}
此代码写在程序初始化部分：
globalKeyboardHook gkh = new globalKeyboardHook();每当我的程序尝试钩住键时，仍然出现此错误：
检测到CallbackOnCollectedDelegate消息：进行了回调
在类型为垃圾收集的委托上
'CaretPosition！Utilities.globalKeyboardHook + keyboardHookProc :: Invoke'。
这可能会导致应用程序崩溃，损坏和数据丢失。什么时候
将委托传递给非托管代码，则必须使委托保持活动状态
托管应用程序，直到确保它们永远不会
叫。
请帮助我解决这个问题。
最佳答案
可能会发生，根本不会发生垃圾回收，并且当您关闭应用程序时，它会导致钩住无效的委托（因为应用程序已卸载）。
您不应该使用finalizer〜globalKeyboardHook释放除分配的内存以外的系统资源，而应使用IDisposable并显式地解除挂钩。否则您可能会摘机
AppDomain.CurrentDomain.ProcessExit
事件