错误:CallbackOnCollectedDelegate -如何找到确切的收集项目

本文关键字：项目 CallbackOnCollectedDelegate 何找 错误 | 更新日期: 2023-09-27 18:02:17

成功运行几分钟后，我的应用程序出现了这个错误。

在类型为垃圾收集的委托上进行了回调"myApp ! myApp.globalKeyboardHook + keyboardHookProc:调用"。

我知道这是因为垃圾收集器已经杀死了一个对象或其他东西，而我的代码仍然引用相同的东西。

如果是这种情况，哪个对象或组件更有可能被GC收集。我怎样才能克服这个错误?(有ref ??)

因为我不能弄清楚代码的哪一部分是负责这个问题，我在这里发布完整的类。(我想这对我的其他类没有问题)

class globalKeyboardHook
    {
        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;
        }
        IntPtr hInstance;
        const int WH_KEYBOARD_LL = 13;
        const int WM_KEYDOWN = 0x100;
        const int WM_SYSKEYDOWN = 0x104;
        public List<Keys> HookedKeys = new List<Keys>();
        IntPtr hhook = IntPtr.Zero;
        // Events
        public event KeyEventHandler KeyDown;
        public globalKeyboardHook()
        {
            hook();
        }
        ~globalKeyboardHook()
        {
            unhook();
        }
        public void hook()
        {
            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 (1 == 1)
                {
                    KeyEventArgs kea = new KeyEventArgs(key);
                    if ((wParam == WM_KEYDOWN || wParam == WM_SYSKEYDOWN) && (KeyDown != null))
                    {
                        KeyDown(this, kea);
                    }
                    if (kea.Handled)
                        return 1;
                }
            }
            return CallNextHookEx(hhook, code, wParam, ref lParam);
        }

        // DLL imports
        [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);
    }
}

错误:CallbackOnCollectedDelegate -如何找到确切的收集项目

    hhook = SetWindowsHookEx(WH_KEYBOARD_LL, hookProc, hInstance, 0);

你肯定很难找到收集的项目，它在你的程序中是不可见的。c#语言在这里有点太友好了。您依赖于它的语法糖来自动创建hookProc的委托对象。这段代码编译成:

    keyboardHookProc $unspeakable = new keyboardHookProc(hookProc);
    hhook = SetWindowsHookEx(WH_KEYBOARD_LL, $unspeakable, hInstance, 0);

这是pinvoke中的一个问题，垃圾收集器不知道$unspeakable委托对象实际上正在被本机代码使用。它只能看到对对象的托管引用。因此，它在第0代垃圾收集发生时立即收集对象。当Windows做钩子回调时。

由您决定是否不能收集此委托对象。使用GCHandle.Alloc()。或者用简单的方法，将它显式地存储在一个变量中。这在这里没有问题，因为你让终结器销毁了钩子:

    IntPtr hhook = IntPtr.Zero;
    keyboardHookProc callback;
    public void hook()
    {
        if (callback != null) throw new InvalidOperationException("Hook already installed");
        if (hInstance == IntPtr.Zero) hInstance = LoadLibrary("User32");
        callback = new keyboardHookProc(hookProc);
        hhook = SetWindowsHookEx(WH_KEYBOARD_LL, callback, hInstance, 0);
    }
    public void unhook()
    {
        UnhookWindowsHookEx(hhook);
        callback = null;
    }
相关文章：