C# Winform中无焦点状态下获取键盘输入或者USB扫描枪数据

类文件：

C#类文件
using System;
using System.Collections.Generic;
using System.Text;
using System.Runtime.InteropServices;
using System.Reflection;

namespace Common
{
    public class BardCodeHooK
    {
        public delegate void BardCodeDeletegate(BarCodes barCode);
        public event BardCodeDeletegate BarCodeEvent;

        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
            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);

        delegate int HookProc(int nCode, Int32 wParam, IntPtr lParam);
        BarCodes barCode = new BarCodes();
        int hKeyboardHook = ;
        string strBarCode = "";

        private int KeyboardHookProc(int nCode, Int32 wParam, IntPtr lParam)
        {
            if (nCode == )
            {
                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();
                    if (GetKeyNameText(barCode.ScanCode * , strKeyName, ) > )
                    {
                        barCode.KeyName = strKeyName.ToString().Trim(new char[] { ' ', '\0' });
                    }
                    else
                    {
                        barCode.KeyName = "";
                    }
                    byte[] kbArray = new byte[];
                    uint uKey = ;
                    GetKeyboardState(kbArray);

                    if (ToAscii(barCode.VirtKey, barCode.ScanCode, kbArray, ref uKey, ))
                    {
                        barCode.Ascll = uKey;
                        barCode.Chr = Convert.ToChar(uKey);
                    }

                    TimeSpan ts = DateTime.Now.Subtract(barCode.Time);

                    if (ts.TotalMilliseconds > )
                    {
                        strBarCode = barCode.Chr.ToString();
                    }
                    else
                    {
                        if ((msg.message & 0xff) ==  && strBarCode.Length > )
                        {
                            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 == )
            {
                //WH_KEYBOARD_LL=13
                hKeyboardHook = SetWindowsHookEx(, new HookProc(KeyboardHookProc), Marshal.GetHINSTANCE(Assembly.GetExecutingAssembly().GetModules()[]), );
            }
            return (hKeyboardHook != );
        }

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

页面中用法：

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Text;
using System.Windows.Forms;

namespace Common
{
    public partial class FrmMain : Form
    {
        BardCodeHooK BarCode = new BardCodeHooK();
        public FrmMain()
        {
            InitializeComponent();
            BarCode.BarCodeEvent += new BardCodeHooK.BardCodeDeletegate(BarCode_BarCodeEvent);
        }

private delegate void ShowInfoDelegate(BardCodeHooK.BarCodes barCode);
        private void ShowInfo(BardCodeHooK.BarCodes barCode)
        {
            if (this.InvokeRequired)
            {
                this.BeginInvoke(new ShowInfoDelegate(ShowInfo), new object[] { barCode });
            }
            else
            {
                textBox1.Text = barCode.KeyName;
                textBox2.Text = barCode.VirtKey.ToString();
                textBox3.Text = barCode.ScanCode.ToString();
                textBox4.Text = barCode.Ascll.ToString();
                textBox5.Text = barCode.Chr.ToString();
                textBox6.Text = barCode.IsValid? barCode.BarCode : "";//是否为扫描枪输入，如果为true则是 否则为键盘输入
                textBox7.Text += barCode.KeyName;
                //MessageBox.Show(barCode.IsValid.ToString());
            }
        }

//C#中判断扫描枪输入与键盘输入

//Private DateTime _dt = DateTime.Now;  //定义一个成员函数用于保存每次的时间点
        //private void textBox1_KeyPress(object sender, KeyPressEventArgs e)
        //{
        //    DateTime tempDt = DateTime.Now;          //保存按键按下时刻的时间点
        //    TimeSpan ts = tempDt .Subtract(_dt);     //获取时间间隔
        //    if (ts.Milliseconds > 50)                           //判断时间间隔，如果时间间隔大于50毫秒，则将TextBox清空
        //        textBox1.Text = "";
        //    dt = tempDt ;
        //}

void BarCode_BarCodeEvent(BardCodeHooK.BarCodes barCode)
        {
            ShowInfo(barCode);
        }

private void FrmMain_Load(object sender, EventArgs e)
        {
            BarCode.Start();
        }

private void FrmMain_FormClosed(object sender, FormClosedEventArgs e)
        {
            BarCode.Stop();
        }

private void textBox6_TextChanged(object sender, EventArgs e)
        {
            if (textBox6.Text.Length > 0)
            {
                MessageBox.Show("条码长度：" + textBox6.Text.Length + "\n条码内容：" + textBox6.Text, "系统提示");
            }
        }
    }
}