在没有焦点的情况下捕获击键

2022-01-13 00:00:00 keyboard c# java

例如使用 winamp(至少在 Windows 上)，您可以在后台使用 winamp 全屏播放游戏，并使用媒体按钮* 来控制声音.Winamp 不需要获得焦点，让游戏继续全屏.

E.g. with winamp (on Windows at least), you can play a game fullscreen with winamp in the background, and use the media buttons* to control the sound. Winamp doesn't need to get focus, allowing the game to continue fullscreen.

我更喜欢用 Java 编写它，但这可能行不通(在 Java afaik 中捕获没有焦点的击键已经很困难了)，所以任何 C# 解决方案也可以.

I'd prefer to write this in Java but that probably isn't going to work (capturing keystrokes without focus is already difficult in Java afaik), so any C# solution is also fine.

所以基本问题是:如何捕捉没有焦点的击键?

So the basic question is: how to capture keystrokes without focus?

*) 我相信后退/前进/停止/邮件/搜索/收藏夹/web/home"按钮被称为媒体按钮，但欢迎使用更好的名称:).

*) I believe the 'back/forward/stop/mail/search/favorites/web/home' buttons are called media buttons, but a better name would be welcome :).

推荐答案

低级 windows hooks 是一种方法.这是一篇 文章，这里是来自 MSDN.

Low-Level windows hooks is one way to do it. Here is one article and here is a little more info from MSDN.

这是该代码的部分视图:

This is a partial view of what that code can look like:

    private IntPtr LowLevelKeyboardHook(int nCode, WindowsMessages wParam, [In] KBDLLHOOKSTRUCT lParam)
    {
        bool callNext = true;

        bool isKeyDown = (wParam == WindowsMessages.KEYDOWN || wParam == WindowsMessages.SYSKEYDOWN);
        bool isKeyUp = (wParam == WindowsMessages.KEYUP || wParam == WindowsMessages.SYSKEYUP);

        if ((nCode >= 0) && (isKeyDown || isKeyUp))
        {
            // the virtual key codes and the winforms Keys have the same enumeration
            // so we can freely cast back and forth between them
            Keys key = (Keys)lParam.vkCode;

            // Do your other processing here...
        }

        // if any handler returned false, trap the message
        return (callNext) ? User32.CallNextHookEx(_mainHook, nCode, wParam, lParam) : _nullNext;
    }


    /// <summary>
    /// Registers the user's LowLevelKeyboardProc with the system in order to
    /// intercept any keyboard events before processed in the regular fashion.
    /// This can be used to log all keyboard events or ignore them.
    /// </summary>
    /// <param name="hook">Callback function to call whenever a keyboard event occurs.</param>
    /// <returns>The IntPtr assigned by the Windows's sytem that defines the callback.</returns>
    private IntPtr RegisterLowLevelHook(LowLevelKeyboardProc hook)
    {
        IntPtr handle = IntPtr.Zero;

        using (Process currentProcess = Process.GetCurrentProcess())
        using (ProcessModule currentModule = currentProcess.MainModule)
        {
            IntPtr module = Kernel32.GetModuleHandle(currentModule.ModuleName);
            handle = User32.SetWindowsHookEx(HookType.KEYBOARD_LL, hook, module, 0);
        }

        return handle;
    }

    /// <summary>
    /// Unregisters a previously registered callback from the low-level chain.
    /// </summary>
    /// <param name="hook">IntPtr previously assigned to the low-level chain.
    /// Users should have stored the value given by 
    /// <see cref="Drs.Interop.Win32.LowLevelKeyboard.RegisterLowLevelHook"/>,
    /// and use that value as the parameter into this function.</param>
    /// <returns>True if the hook was removed, false otherwise.</returns>
    private bool UnregisterLowLevelHook(IntPtr hook)
    {
        return User32.UnhookWindowsHookEx(hook);
    }

只需实现所需的所有 P/Invoke 声明，它就可以工作.我在我的应用程序中使用了这种方法，并且效果很好.

Just implement all the P/Invoke declarations needed, and it should work. I use this approach in my application and it works fine.

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