Question

我找到了一种捕获C＃中Print Screen按钮的方法。按下Alt + Print Screen时会弹出一个简单的消息框，说明已按下按键。但它在几秒钟之后没有响应。我不知道为什么会这样。

这是我使用的代码：

static class Program
{
    /// <summary>
    /// The main entry point for the application.
    /// </summary>
    [STAThread]
    static void Main()
    {
        Application.EnableVisualStyles();
        Application.SetCompatibleTextRenderingDefault(false);
        _hookID = SetHook(_proc);
        Application.Run(new Form1());
        UnhookWindowsHookEx(_hookID);  
    }

    /****************************************/
    private const int WH_KEYBOARD_LL = 13;
    //private const int WH_KEYBOARD_LL = 13;  
    private const int WM_KEYDOWN = 0x0100;
    private const int VK_F1 = 0x70;
    private static LowLevelKeyboardProc _proc = HookCallback;
    private static IntPtr _hookID = IntPtr.Zero;

    private static IntPtr SetHook(LowLevelKeyboardProc proc)
    {
        using (Process curProcess = Process.GetCurrentProcess())
        using (ProcessModule curModule = curProcess.MainModule)
        {
            return SetWindowsHookEx(WH_KEYBOARD_LL, proc,
                GetModuleHandle(curModule.ModuleName), 0);
        }
    }

    private delegate IntPtr LowLevelKeyboardProc(
        int nCode, IntPtr wParam, IntPtr lParam);

    private static IntPtr HookCallback(
        int nCode, IntPtr wParam, IntPtr lParam)
    {

        if (nCode >= 0)
        {
            Keys number = (Keys)Marshal.ReadInt32(lParam);
            if (number == Keys.PrintScreen)
            {
                if ((wParam == (IntPtr)260 && Keys.Alt == Control.ModifierKeys && number == Keys.PrintScreen))
                {
                    MessageBox.Show("You pressed alt+ print screen");
                }
            }

        }
        return CallNextHookEx(IntPtr.Zero, nCode, wParam, lParam);

    }

    [DllImport("user32.dll", CharSet = CharSet.Auto, SetLastError = true)]
    private static extern IntPtr SetWindowsHookEx(int idHook,
        LowLevelKeyboardProc lpfn, IntPtr hMod, uint dwThreadId);

    [DllImport("user32.dll", CharSet = CharSet.Auto, SetLastError = true)]
    [return: MarshalAs(UnmanagedType.Bool)]
    private static extern bool UnhookWindowsHookEx(IntPtr hhk);

    [DllImport("user32.dll", CharSet = CharSet.Auto, SetLastError = true)]
    private static extern IntPtr CallNextHookEx(IntPtr hhk, int nCode,
        IntPtr wParam, IntPtr lParam);

    [DllImport("kernel32.dll", CharSet = CharSet.Auto, SetLastError = true)]
    private static extern IntPtr GetModuleHandle(string lpModuleName); 
}

有没有人知道为什么它会挂在消息框之后？

Answer 1

在钩子回调完成执行之前，Windows无法调度下一个键盘消息。很明显，你不想要使用阻止回调的MessageBox.Show（）。 Windows在声明代码被破坏并禁用挂钩之前会持续几秒钟。

改为使用Debug.Print（）。

程序在几秒钟内没有响应

1 个答案: