一、条形码的读取
用过键盘口式的扫条码工具的朋友就知道，它就如同在鍵盘上按下数字鍵一样，基本不需任何编程和处理。但如果你使用的是其它接口的话，可能你就要为该设备编写通讯代码了。以下有一段简单的25针串口的条码读取器通讯代码。
Option Explicit
Dim sData As String
Private Sub Form_Load()
With MSComm1
.CommPort = 3 设为COM3，试运行的系统而定，你可提供一个Combox让用户选择。
.PortOpen = True 打开通讯端口
End With
End Sub
Private Sub MSComm1_OnComm()
Dim EndPos As Integer
Select Case MSComm1.CommEvent
Case comEvReceive 当有数据传送过来时
sData = sData & Trim(MSComm1.Input)
检索回车,通常读卡机每组数据結尾都返回一个回车作为结束符
EndPos = InStr(1, sData, Chr(13))
If EndPos = 0 Then 如果未结束就继续努力
Else 读完一组。
lblBarCode.Caption = sData 显示一组条形码
With lstBarCode
.AddItem Mid(sData, 1, EndPos - 1) 添加一组条形码到列表
End With
sData = "" 清空
End If
End Select
End Sub
Private Sub cmdEnd_Click()
MSComm1.PortOpen = False 关闭端口
End
End Sub
二、条形码的生成
看完以上关于条码读取的代码是否觉得很容易呢？对，在VB上编程本来就不难。以下关于条形码生成的代码也是很容易理解，只需使用一个OFFICE的附带的BarCode控件就可以轻松打印出11种不同标准的条形码，足以满足我们的要求。下面是条形码生成的代码及有关说明。
源代码主要由两个窗体（frmMain主窗体和frmOption条码设置窗体）和两个模块组成(modGetScreen.bas、SysDLG32.bas)。考虑到篇幅，这里只列出部分较为关键的代码。
新建一个标准工程，添加一个名为(Microsoft Access BarCode Control9)的条形码部件，并添加一个条码控件到窗口，并将窗口改名为frmMain，如图所示。由于控件比较多，这里不便细说，详细内容请看源代码。
模块modGetScreen.bas代码如下：
Option Explicit
声明BitBlt、GetDesktopWindow、GetWindowDC、ReleaseDC这几个API函数略
Public RegUser As Boolean
Sub GetObjImage1(Obj As Object, OwnerForm As PictureBox, Picture1 As PictureBox)
hDC
Dim hWndDesk As Long
Dim hDCDesk As Long
区域表达变量
Dim x As Long
Dim y As Long
Dim w As Long
Dim h As Long
x = Obj.LeftScreen.TwipsPerPixelX
y = Obj.TopScreen.TwipsPerPixelY
w = Obj.WidthScreen.TwipsPerPixelX
h = Obj.HeightScreen.TwipsPerPixelY
hDCDesk = OwnerForm.hdc
取出图像
Call BitBlt(Picture1.hdc, 0, 0, w, h, hDCDesk, x, y, VBSrcCopy)
Call ReleaseDC(hWndDesk, hDCDesk)
End Sub
主窗体frmMain.frm部分代码如下：
Private Sub cmdPrint_Click()
生成条形码图像
Dim r As Long, i As Integer, t As String,cfile As String 临时变量
t = BarCode
For i = 0 To Val(Times) - 1
BarCode1.Value = BarCode + i
DoEvents
Picture1.Refresh
GetObjImage1 BarCode1, Conel, Picture1
If RegUser = False Then 如果未注册添加MASK标记
Picture1.PaintPicture Picture2.Picture, 300, 300
End If
If Dir(SavePath, VBDirectory) = "" Then MkDir SavePath
SavePath = SavePath & IIf(Right(SavePath, 1) <> "", "", "")
cfile = SavePath & BarCode1.Value & ".bmp"
SavePicture Picture1.Image, cfile 将条形码保存为图像文件以便打印
Next
BarCode = t
End Sub
条形码设置窗体frmOption.frm代码如下：
Option Explicit
条形码设置模块
Private Sub cboBig_Click()
BarCode1.Style = cboBig.ListIndex 改变标准
End Sub
Private Sub cboDirection_Click()
BarCode1.Direction = cboDirection.ListIndex 改变方向
End Sub
Private Sub cboLine_Click()
BarCode1.LineWeight = cboLine.ListIndex 改变线宽
End Sub
Private Sub cboSmall_Click()
BarCode1.SubStyle = cboSmall.ListIndex 改变样式
End Sub
Private Sub Check1_Click()
BarCode1.ShowData = Check1.Value 是否显示数据
End Sub
Private Sub cmdChange_Click()
设置长、宽大小
BarWidth = BarCode1.Height
BarHeight = BarCode1.Width
cmdRefresh_Click
End Sub
Private Sub cmdOK_Click()
传送条形码设定到主界面
With frmMain.BarCode1
.LineWeight = BarCode1.LineWeight
.Style = BarCode1.Style
.SubStyle = BarCode1.SubStyle
.Direction = BarCode1.Direction
.Width = BarCode1.Width
.Height = BarCode1.Height
.ShowData = BarCode1.ShowData
Me.Hide
End With
With frmMain
.Picture1.Width = .BarCode1.Width
.Picture1.Height = .BarCode1.Height
.Conel.Width = .BarCode1.Width
.Conel.Height = .BarCode1.Height
End With
End Sub
Private Sub cmdRefresh_Click()
BarCode1.Width = BarWidth
BarCode1.Height = BarHeight
End Sub
Private Sub Form_Load()
LoadBarInfo
BarWidth = BarCode1.Width
BarHeight = BarCode1.Height
End Sub
Sub LoadBarInfo() 初始化选项
LoadBigClass cboBig
LoadSmallClass cboSmall
LoadLineSize cboLine
LoadDirection cboDirection
End Sub
Sub LoadBigClass(cbo As ComboBox) 条码标准
With cbo
.AddItem "UPC-A"
.AddItem "UPC-E"
.AddItem "EAN-13"
.AddItem "EAN-8"
.AddItem "Case Code"
.AddItem "Codabar (NW-T)"
.AddItem "Code-39"
.AddItem "Code-128"
.AddItem "U.S. Postnet"
.AddItem "U.S. Postal FIM"
.AddItem "JP Post"
.ListIndex = 2
End With
End Sub
Sub LoadSmallClass(cbo As ComboBox) 条码样式
With cbo
.AddItem "Standard"
.AddItem "2-Digit Supplement"
.AddItem "5-Digit Supplement"
.AddItem "POS Case Code"
.ListIndex = 0
End With
End Sub
许多人在编写数据库应用程序时，都想要加上条形码功能加强工作效率，尤其是销售管理，图书馆管理这类流量大的应用软件，但由于条形码技术难以掌握、标谁又多以及过去的技术种种原因，使得许多人望而却步。本文介绍的一套简单实用的条形码解决方法，希望能帮助各位完善软件系统的功能。