无焦点下获取条码枪返回值的Hook（改良版）代码,CSharp代码库,德仔网

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【CSharp】无焦点下获取条码枪返回值的Hook（改良版）
作者:我叫李冠男 / 发布于2013/12/26/ 617
此版本是改良过网络上流行的代码的 1.去除了.net4.0的MDA风险; 2.修正了原有代码中，扫描出的内容有问题部分
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Runtime.InteropServices;
using System.Reflection;

namespace BookLibraryManagement.CommonTools
{
  class BarCodeHook
  {
    public delegate void BarCodeDelegate(BarCodes barCode);
    public event BarCodeDelegate BarCodeEvent;

    public struct BarCodes
    {
      public int VirtKey;   //虚拟码 
      public int ScanCode;   //扫描码 
      public string KeyName;  //键名 
      public uint AscII;    //AscII 
      public char Chr;     //字符 

      public string BarCode;  //条码信息 
      public bool IsValid;   //条码是否有效 
      public DateTime Time;  //扫描时间 
    }

    private struct EventMsg
    {
      public int message;
      public int paramL;
      public int paramH;
      public int Time;
      public int hwnd;
    }

    [DllImport("user32.dll", CharSet = CharSet.Auto, CallingConvention = CallingConvention.StdCall)]
    private static extern int SetWindowsHookEx(int idHook, HookProc lpfn, IntPtr hInstance, int threadId);

    [DllImport("user32.dll", CharSet = CharSet.Auto, CallingConvention = CallingConvention.StdCall)]
    private static extern bool UnhookWindowsHookEx(int idHook);

    [DllImport("user32.dll", CharSet = CharSet.Auto, CallingConvention = CallingConvention.StdCall)]
    private static extern int CallNextHookEx(int idHook, int nCode, Int32 wParam, IntPtr lParam);

    [DllImport("user32", EntryPoint = "GetKeyNameText")]
    private static extern int GetKeyNameText(int lParam, StringBuilder lpBuffer, int nSize);

    [DllImport("user32", EntryPoint = "GetKeyboardState")]
    private static extern int GetKeyboardState(byte[] pbKeyState);

    [DllImport("user32", EntryPoint = "ToAscii")]
    private static extern bool ToAscii(int VirtualKey, int ScanCode, byte[] lpKeyState, ref uint lpChar, int uFlags);

    delegate int HookProc(int nCode, Int32 wParam, IntPtr lParam);

    BarCodes barCode = new BarCodes();
    int hKeyboardHook = 0;
    //此处使用char List 避免了原有代码中扫描出的结果是乱码的情况
    List<char> _barcode = new List<char>(100);
    private int KeyboardHookProc(int nCode, Int32 wParam, IntPtr lParam)
    {
      if (nCode == 0)
      {
        EventMsg msg = (EventMsg)Marshal.PtrToStructure(lParam, typeof(EventMsg));

        if (wParam == 0x100)  //WM_KEYDOWN = 0x100 
        {
          barCode.VirtKey = msg.message & 0xff; //虚拟码 
          barCode.ScanCode = msg.paramL & 0xff; //扫描码 

          StringBuilder strKeyName = new StringBuilder(255);
          if (GetKeyNameText(barCode.ScanCode * 65536, strKeyName, 255) > 0)
          {
            barCode.KeyName = strKeyName.ToString().Trim(new char[] { ' ', '\0' });
          }
          else
          {
            barCode.KeyName = "";
          }

          byte[] kbArray = new byte[256];
          uint uKey = 0;
          GetKeyboardState(kbArray);
          if (ToAscii(barCode.VirtKey, barCode.ScanCode, kbArray, ref uKey, 0))
          {
            barCode.AscII = uKey;
            barCode.Chr = Convert.ToChar(uKey);
          }

          if (DateTime.Now.Subtract(barCode.Time).TotalMilliseconds > 100)
          {
            _barcode.Clear();
          }
          else
          {
            if ((msg.message & 0xff) == 13 && _barcode.Count > 0)  //回车 
            {
              barCode.BarCode = new String(_barcode.ToArray());
              barCode.IsValid = true;
            }
            _barcode.Add(Convert.ToChar(msg.message & 0xff));
          }

          barCode.Time = DateTime.Now;
          if (BarCodeEvent != null) BarCodeEvent(barCode);  //触发事件 
          barCode.IsValid = false;
        }
      }
      return CallNextHookEx(hKeyboardHook, nCode, wParam, lParam);
    }

    //增加了一个静态变量，放置GC将钩子回收掉
    private static HookProc hookproc;
    // 安装钩子 
    public bool Start()
    {
      if (hKeyboardHook == 0)
      {
        hookproc = new HookProc(KeyboardHookProc);
        //WH_KEYBOARD_LL = 13 
        hKeyboardHook = SetWindowsHookEx(13, hookproc, Marshal.GetHINSTANCE(Assembly.GetExecutingAssembly().GetModules()[0]), 0);
      }
      return (hKeyboardHook != 0);
    }

    // 卸载钩子 
    public bool Stop()
    {
      if (hKeyboardHook != 0)
      {
        return UnhookWindowsHookEx(hKeyboardHook);
      }
      return true;
    }
  }
}
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