我正在使用全局键盘钩子类。此类允许检查键盘键是否按下任何位置。过了一段时间我遇到了错误：
**CallbackOnCollectedDelegate was detected**
A callback was made on a garbage collected delegate of type 'Browser!Utilities.globalKeyboardHook+keyboardHookProc::Invoke'. This may cause application crashes, corruption and data loss. When passing delegates to unmanaged code, they must be kept alive by the managed application until it is guaranteed that they will never be called.
这是globalkeyboardHook类：
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;
public List<Keys> HookedKeys = new List<Keys>();
IntPtr hhook = IntPtr.Zero;
public event KeyEventHandler KeyDown;
public event KeyEventHandler KeyUp;
public globalKeyboardHook()
{
hook();
}
~globalKeyboardHook()
{
unhook();
}
public void hook()
{
IntPtr hInstance = LoadLibrary("User32");
hhook = SetWindowsHookEx(WH_KEYBOARD_LL, hookProc, hInstance, 0);
}
public void unhook()
{
UnhookWindowsHookEx(hhook);
}
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);
}
[DllImport("user32.dll")]
static extern IntPtr SetWindowsHookEx(int idHook, keyboardHookProc callback, IntPtr hInstance, uint threadId);
[DllImport("user32.dll")]
static extern bool UnhookWindowsHookEx(IntPtr hInstance);
[DllImport("user32.dll")]
static extern int CallNextHookEx(IntPtr idHook, int nCode, int wParam, ref keyboardHookStruct lParam);
[DllImport("kernel32.dll")]
static extern IntPtr LoadLibrary(string lpFileName);
#endregion
任何想法如何解决？该程序运行良好，但一段时间后程序冻结蚂蚁我得到这个错误。
答案 0 :(得分：31)
hhook = SetWindowsHookEx(WH_KEYBOARD_LL, hookProc, hInstance, 0);
有你的问题。您依靠C＃语法糖来自动创建 hookProc 的委托对象。实际代码生成如下所示：
keyboardHookProc $temp = new keyboardHookProc(hookProc);
hhook = SetWindowsHookEx(WH_KEYBOARD_LL, $temp, hInstance, 0);
只有一个对委托对象的引用，$ temp。但它是局部变量，只要你的hook（）方法停止执行并返回就会消失。垃圾收集器无法看到Windows对它有“引用”，它无法探测非托管代码以获取引用。因此，下次垃圾收集器运行时，委托对象将被销毁。当Windows进行钩子回调时，这就是kaboom。内置的MDA检测到问题并在程序崩溃之前生成有用的诊断信息。
您需要创建一个足够长的委托对象的附加引用。例如，您可以使用GCHandle。或者更简单，只需自己存储引用，以便垃圾收集器始终可以看到引用。在您的班级中添加一个字段。使其静止是确保无法收集对象的可靠方法：
private static keyboardHookProc callbackDelegate;
public void hook()
{
if (callbackDelegate != null) throw new InvalidOperationException("Can't hook more than once");
IntPtr hInstance = LoadLibrary("User32");
callbackDelegate = new keyboardHookProc(hookProc);
hhook = SetWindowsHookEx(WH_KEYBOARD_LL, callbackDelegate, hInstance, 0);
if (hhook == IntPtr.Zero) throw new Win32Exception();
}
public void unhook()
{
if (callbackDelegate == null) return;
bool ok = UnhookWindowsHookEx(hhook);
if (!ok) throw new Win32Exception();
callbackDelegate = null;
}
无需pinvoke FreeLibrary，在程序终止之前，始终会加载user32.dll。
答案 1 :(得分：0)
很快就完成了！ 在 Hans Passant的答案和GitHub项目之后，这是一个具有最新修复程序（定义和实现）的良好工作实现。
//file Win32Api.cs
using System;
using System.Runtime.InteropServices;
using YourProjectNamespace.Hooks;
namespace YourProjectNamespace
{
public delegate int keyboardHookProc(int code, int wParam, ref keyboardHookStruct lParam);
/// <summary>
/// Pcursor info
/// </summary>
[StructLayout(LayoutKind.Sequential)]
public struct PCURSORINFO
{
public Int32 Size;
public Int32 Flags;
public IntPtr Cursor;
public POINTAPI ScreenPos;
}
/// <summary>
/// Point
/// </summary>
[StructLayout(LayoutKind.Sequential)]
public struct POINTAPI
{
public int x;
public int y;
}
/// <summary>
/// keyboard hook struct
/// </summary>
public struct keyboardHookStruct
{
public int dwExtraInfo;
public int flags;
public int scanCode;
public int time;
public int vkCode;
}
/// <summary>
/// Wrapper for windows 32 calls.
/// </summary>
public class Win32Api
{
public const Int32 CURSOR_SHOWING = 0x00000001;
public const int WH_KEYBOARD_LL = 13;
public const int WM_KEYDOWN = 0x100;
public const int WM_KEYUP = 0x101;
public const int WM_SYSKEYDOWN = 0x104;
public const int WM_SYSKEYUP = 0x105;
[DllImport("user32.dll")]
public static extern bool GetCursorInfo(out PCURSORINFO cinfo);
[DllImport("user32.dll")]
public static extern bool DrawIcon(IntPtr hDC, int X, int Y, IntPtr hIcon);
[DllImport("winmm.dll")]
private static extern int mciSendString(string MciComando, string MciRetorno, int MciRetornoLeng, int CallBack);
[DllImport("user32")]
private static extern int GetKeyboardState(byte[] pbKeyState);
[DllImport("user32.dll", CharSet = CharSet.Auto, CallingConvention = CallingConvention.StdCall)]
private static extern short GetKeyState(int vKey);
[DllImport("user32")]
public static extern int ToAscii(
int uVirtKey,
int uScanCode,
byte[] lpbKeyState,
byte[] lpwTransKey,
int fuState);
[DllImport("user32.dll", CharSet = CharSet.Auto,
CallingConvention = CallingConvention.StdCall)]
public static extern int CallNextHookEx(
IntPtr idHook,
int nCode,
int wParam,
ref keyboardHookStruct lParam);
[DllImport("user32.dll", CharSet = CharSet.Auto,
CallingConvention = CallingConvention.StdCall, SetLastError = true)]
public static extern int UnhookWindowsHookEx(IntPtr idHook);
[DllImport("user32.dll", CharSet = CharSet.Auto,
CallingConvention = CallingConvention.StdCall, SetLastError = true)]
public static extern IntPtr SetWindowsHookEx(
int idHook,
keyboardHookProc lpfn,
IntPtr hMod,
int dwThreadId);
[DllImport("kernel32.dll")]
public static extern IntPtr LoadLibrary(string dllToLoad);
//Constants
} // class Win32
**File GlobalKeyboardHook.cs**
using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Runtime.InteropServices;
using System.Windows.Forms;
using log4net;
namespace ScreenRecorder.Hooks
{
public class GlobalKeyboardHook
{
private static readonly ILog log = LogManager.GetLogger(typeof (GlobalKeyboardHook).Name);
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;
public List<Keys> HookedKeys = new List<Keys>();
private IntPtr keyboardHook = IntPtr.Zero;
/// <summary>
public GlobalKeyboardHook()
{
Hook();
}
~GlobalKeyboardHook() {
Unhook();
}
public event KeyEventHandler KeyDown;
public event KeyEventHandler KeyUp;
public int HookProc(int nCode, int wParam, ref keyboardHookStruct lParam)
{
if (nCode >= 0)
{
var key = (Keys) lParam.vkCode;
if (HookedKeys.Contains(key))
{
var kArgs = new KeyEventArgs(key);
if ((wParam == Win32Api.WM_KEYDOWN || wParam == Win32Api.WM_SYSKEYDOWN) && (KeyDown != null))
{
KeyDown(this, kArgs);
}
else if ((wParam == Win32Api.WM_KEYUP || wParam == Win32Api.WM_SYSKEYUP) && (KeyUp != null))
{
KeyUp(this, kArgs);
}
if (kArgs.Handled)
return 1;
}
}
return Win32Api.CallNextHookEx(keyboardHook, nCode, wParam, ref lParam);
}
public void Hook()
{
// Create an instance of HookProc.
//if (callbackDelegate != null) throw new InvalidOperationException("Multiple hooks are not allowed!");
IntPtr hInstance = Win32Api.LoadLibrary("User32");
callbackDelegate = new keyboardHookProc(HookProc);
//install hook
keyboardHook = Win32Api.SetWindowsHookEx( Win32Api.WH_KEYBOARD_LL, callbackDelegate, hInstance, 0);
//If SetWindowsHookEx fails.
if (keyboardHook == IntPtr.Zero)
{
//Returns the error code returned by the last unmanaged function called using platform invoke that has the DllImportAttribute.SetLastError flag set.
var errorCode = Marshal.GetLastWin32Error();
log.Error("Unable to install keyboard hook.", new Win32Exception(errorCode));
}
}
/// <summary>
/// Unsubscribe for keyboard hook
/// </summary>
public void Unhook()
{
if (callbackDelegate == null) return;
if (keyboardHook != IntPtr.Zero)
{
//uninstall hook
var retKeyboard = Win32Api.UnhookWindowsHookEx(keyboardHook);
//reset invalid handle
keyboardHook = IntPtr.Zero;
//if failed and exception must be thrown
if (retKeyboard == 0)
{
//Returns the error code returned by the last unmanaged function called using platform invoke that has the DllImportAttribute.SetLastError flag set.
var errorCode = Marshal.GetLastWin32Error();
//Initializes and throws a new instance of the Win32Exception class with the specified error.
log.Error("Error while uninstalling keyboard hook", new Win32Exception(errorCode));
}
}
callbackDelegate = null;
}
}
}