vb 调用DLL问题

fxhswu 2012-03-22 03:11:05

dll内有以下函数：

int DecCard (int ComPort,int CardNumLength,unsigned char *CardNum,int DecMoney)

'入口参数:
' CardNumLength：显示卡号长度（字节数），最小可设置为10，最大可设置为17
' CardNum: 显示卡号(ASCII码)，显示卡号长度等于CardNumLength
' DecMoney: 要扣除的金额

在vb中这样声明对吗？
Public Declare Function DecCard Lib "C:\WINDOWS\SYSTEM32\SmartCom411SFJ.dll" (ByVal ComPort As Long, ByVal CardNumLength As Long, ByRef CardNum As Byte, ByRef DecMoney As Long) As Long

Dim DecCardRuturn as Long
Dim CardNum() As Byte
DecMoney =Val(Text11.Text)
CardNum() = StrConv(Trim(Text3.Text) & vbNullChar, vbFromUnicode) ' 将字符串转换成字节数组
DecCardRuturn = SMT_DecCard(ComPort, CardNumLength, CardNum(0), DecMoney)

怎么老是操作不成功啊？请各位大虾指点指点！

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worldy 2012-03-23

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int DecCard (int ComPort,int CardNumLength,unsigned char *CardNum,int DecMoney)
'入口参数:
' CardNumLength：显示卡号长度（字节数），最小可设置为10，最大可设置为17
' CardNum: 显示卡号(ASCII码)，显示卡号长度等于CardNumLength
' DecMoney: 要扣除的金额

Public Declare Function DecCard Lib "C:\WINDOWS\SYSTEM32\SmartCom411SFJ.dll" (ByVal ComPort As Long, ByVal CardNumLength As Long, Byval CardNum As string, Byval DecMoney As Long) As Long

东方之珠 2012-03-23

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[Quote=引用 3 楼 fxhswu 的回复:]
不好意思，再问一下楼主，我把DLL内函数中参数 &写掉了，应该是int DecCard (int ComPort,int CardNumLength,unsigned char *CardNum,int &DecMoney，是否应该把DecMoney 前面的 ByVal 改成 ByRef ?即
Public Declare Function DecCard Lib "C:\WIN……
[/Quote]
没错，是这样。

Public Declare Function DecCard Lib "C:\WINDOWS\SYSTEM32\SmartCom411SFJ.dll" (ByVal ComPort As Long, ByVal CardNumLength As Long, ByRef CardNum As Byte, ByRef DecMoney As Long) As Long

    

  Dim DecCardRuturn as Long

  Dim CardNum() As Byte

  DecMoney =Clng(Text11.Text)

  CardNum() = StrConv(Text3.Text & chr(0), vbFromUnicode) ' 将字符串转换成字节数组

  DecCardRuturn = SMT_DecCard(ComPort, CardNumLength, CardNum(0), DecMoney)

fxhswu 2012-03-23

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不好意思，再问一下楼主，我把DLL内函数中参数 &写掉了，应该是int DecCard (int ComPort,int CardNumLength,unsigned char *CardNum,int &DecMoney，是否应该把DecMoney 前面的 ByVal 改成 ByRef ?即
Public Declare Function DecCard Lib "C:\WINDOWS\SYSTEM32\SmartCom411SFJ.dll" (ByVal ComPort As Long, ByVal CardNumLength As Long, ByRef CardNum As Byte, ByRef DecMoney As Long) As Long

东方之珠 2012-03-22

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DecMoney =Clng(Text11.Text)

东方之珠 2012-03-22

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Public Declare Function DecCard Lib "C:\WINDOWS\SYSTEM32\SmartCom411SFJ.dll" (ByVal ComPort As Long, ByVal CardNumLength As Long, ByRef CardNum As Byte, ByVal DecMoney As Long) As Long

    

  Dim DecCardRuturn as Long

  Dim CardNum() As Byte

  DecMoney =Val(Text11.Text)

  CardNum() = StrConv(Text3.Text & chr(0), vbFromUnicode) ' 将字符串转换成字节数组

  DecCardRuturn = SMT_DecCard(ComPort, CardNumLength, CardNum(0), DecMoney)