捕获按键没有焦点 [英] Capturing keystrokes without focus

问题描述

例如。与AOL的Winamp（在Windows上至少），你可以玩游戏全屏背景AOL的Winamp，并使用多媒体按键*来控制声音。 Winamp的不需要获得焦点，允许比赛继续进行全屏。

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.

我宁愿用Java写这不过那可能是行不通的（ 。捕捉按键没有焦点已经很难在Java中据我所知），所以任何C＃解决方案也未尝不可。

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，基本的问题是：如何捕捉击键没有焦点

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

*）我相信前进/后退/停止/邮件/搜索/收藏夹/ Web /主页按钮被称为多媒体按键，而是一个更好的名字是欢迎的。

*) 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

低级别的Windows钩子就是做这件事。这里有一个文章，这里是从的MSDN

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

这是一个什么样的代码可以看起来像一个局部视图：

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);
    }

就实现所有的P / Invoke需要声明，它应该工作。
我用这个方法在我的应用程序，它工作正常。

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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