转发 https://www.cnblogs.com/TBW-Superhero/p/8659306.html
1.扫描枪获取数据原理基本相当于键盘数据，获取扫描枪扫描出来的数据，一般分为两种实现方式。
a）文本框输入获取焦点，扫描后自动显示在文本框内。
b）使用键盘钩子，勾取扫描枪虚拟按键，根据按键频率进行手动输入和扫描枪扫描判断。
2.要实现系统钩子其实很简单，调用三个Win32的API即可。
SetWindowsHookEx 用于设置钩子。（设立一道卡子，盘查需要的信息）
CallNextHookEx 用于传递钩子（消息是重要的，所以从哪里来，就应该回到哪里去，除非你决定要封锁消息）
UnhookWindowsHookEx 卸载钩子（卸载很重要，卡子设多了会造成拥堵）
版本一：
using System;
using System.Collections.Generic;
using System.Text;
using System.Runtime.InteropServices;
using System.Reflection;
using System.Diagnostics;
namespace SaomiaoTest2
{
/// <summary>
/// 获取键盘输入或者USB扫描枪数据 可以是没有焦点 应为使用的是全局钩子
/// USB扫描枪 是模拟键盘按下
/// 这里主要处理扫描枪的值，手动输入的值不太好处理
/// </summary>
public class BardCodeHooK
{
public delegate void BardCodeDeletegate(BarCodes barCode);
public event BardCodeDeletegate BarCodeEvent;
//定义成静态，这样不会抛出回收异常
private static HookProc hookproc;
public struct BarCodes
{
public int VirtKey;//虚拟吗
public int ScanCode;//扫描码
public string KeyName;//键名
public uint Ascll;//Ascll
public char Chr;//字符
public string BarCode;//条码信息 保存最终的条码
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 IParam, 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[] lpKeySate, ref uint lpChar, int uFlags);
[DllImport("kernel32.dll")]
public static extern IntPtr GetModuleHandle(string name);
delegate int HookProc(int nCode, Int32 wParam, IntPtr lParam);
BarCodes barCode = new BarCodes();
int hKeyboardHook = 0;
string strBarCode = "";
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;//虚拟吗
barCode.ScanCode = msg.paramL & 0xff;//扫描码
StringBuilder strKeyName = new StringBuilder(225);
if (GetKeyNameText(barCode.ScanCode * 65536, strKeyName, 255) > 0)
{
barCode.KeyName = strKeyName.ToString().Trim(new char[] { ' ', ' ' });
}
else
{
barCode.KeyName = "";
}
byte[] kbArray = new byte[256];
uint uKey = 0;
GetKeyboardState(kbArray);
if (ToAscii(barCode.VirtKey, barCode.ScanCode, kbArray, ref uKey, 0))
{
barCode.Ascll = uKey;
barCode.Chr = Convert.ToChar(uKey);
}
TimeSpan ts = DateTime.Now.Subtract(barCode.Time);
if (ts.TotalMilliseconds > 50)
{//时间戳，大于50 毫秒表示手动输入
strBarCode = barCode.Chr.ToString();
}
else
{
if ((msg.message & 0xff) == 13 && strBarCode.Length > 3)
{//回车
barCode.BarCode = strBarCode;
barCode.IsValid = true;
}
strBarCode += barCode.Chr.ToString();
}
barCode.Time = DateTime.Now;
if (BarCodeEvent != null)
BarCodeEvent(barCode);//触发事件
barCode.IsValid = false;
}
}
return CallNextHookEx(hKeyboardHook, nCode, wParam, lParam);
}
//安装钩子
public bool Start()
{
if (hKeyboardHook == 0)
{
hookproc = new HookProc(KeyboardHookProc);
//GetModuleHandle 函数 替代 Marshal.GetHINSTANCE
//防止在 framework4.0中 注册钩子不成功
IntPtr modulePtr = GetModuleHandle(Process.GetCurrentProcess().MainModule.ModuleName);
//WH_KEYBOARD_LL=13
//全局钩子 WH_KEYBOARD_LL
// hKeyboardHook = SetWindowsHookEx(13, hookproc, Marshal.GetHINSTANCE(Assembly.GetExecutingAssembly().GetModules()[0]), 0);
hKeyboardHook = SetWindowsHookEx(13, hookproc, modulePtr, 0);
}
return (hKeyboardHook != 0);
}
//卸载钩子
public bool Stop()
{
if (hKeyboardHook != 0)
{
return UnhookWindowsHookEx(hKeyboardHook);
}
return true;
}
}
}
在实践过程中，发现版本一的代码只能扫描条形码，如伴随二维码中的字母出现就不能正确获取数据。
版本二：
按 Ctrl+C 复制代码
按 Ctrl+C 复制代码
版本二中的代码，实践中发现出现了获取扫描数据却省略“+”加号的情况出现。
因此在版本二中备选处添加
//判断是+ 强制添加+
else if (_key.Length == 5 && msg.paramH == 0&&msg.paramL==78&&msg.message==107)// && msg.paramH == 0
{
// 根据键盘状态和shift缓存判断输出字符
_cur = Convert.ToChar('+').ToString();
_result[_result.Count - 1] += _cur;
}
3.winform在无焦点情况下的使用方式：
using BarcodeScanner;
using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;
namespace BarCodeTest
{
public partial class Form1 : Form
{
private ScanerHook listener = new ScanerHook();
public Form1()
{
InitializeComponent();
listener.ScanerEvent += Listener_ScanerEvent;
}
private void Listener_ScanerEvent(ScanerHook.ScanerCodes codes)
{
textBox3.Text = codes.Result;
}
private void Form1_Load(object sender, EventArgs e)
{
listener.Start();
}
private void Form1_FormClosed(object sender, FormClosedEventArgs e)
{
listener.Stop();
}
}
}