Example: ActiveX client application using helper methods for data type conversion

Generally, data type conversion between ActiveX (Visual Basic and VBScript) and Java methods occurs automatically. converting data types. However, the byte helper function and currency helper function are provided for cases where automatic conversion is not possible:

• Byte helper function Because the Java Byte data type is signed (-127 through 128) and the Visual Basic Byte data type is unsigned (0 through 255), convert unsigned Bytes to a Visual Basic Integers, which look like the Java signed byte. To make this conversion, we can use the following helper function:

   Private Function GetIntFromJava Byte(Byte jByte) as Integer
         GetIntFromJava Byte = (CInt(jByte) + 128) Mod 256 - 128 End Function
  

• Currency helper function Visual Basic 6.0 cannot properly handle 64-bit integers like Java methods can (as the Long data type). Therefore, Visual Basic uses the Currency type, which is intrinsically a 64-bit data type. The only side effect of using the Currency type (the Variant type VT_CY) is that a decimal point is inserted into the type. To extract and manipulate the 64-bit Long value in Visual Basic, use code like the following example. For more details on this technique for converting Currency data types, see Q189862, "HOWTO: Do 64-bit Arithmetic in VBA", on the Microsoft Knowledge Base.

  ' Currency Helper Types Private Type MungeCurr
      Value As Currency End Type Private Type Munge2Long
      LoValue As Long
      HiValue As Long End Type
  
  ' Currency Helper Functions Private Function CurrToText(ByVal Value As Currency) As String
      Dim Temp As String, L As Long
      Temp = Format$(Value, "#.0000")
      L = Len(Temp)
      Temp = Left$(Temp, L - 5) & Right$(Temp, 4)
      Do While Len(Temp) > 1 And Left$(Temp, 1) = "0"
          Temp = Mid$(Temp, 2)
      Loop
      Do While Len(Temp) > 2 And Left$(Temp, 2) = "-0"
          Temp = "-" & Mid$(Temp, 3)
      Loop
      CurrToText = Temp End Function
   Private Function TextToCurr(ByVal Value As String) As Currency
      Dim L As Long, Negative As Boolean
      Value = Trim$(Value)
      If Left$(Value, 1) = "-" Then
          Negative = True
          Value = Mid$(Value, 2)
      End If
      L = Len(Value)
      If L < 4 Then
          TextToCurr = CCur(IIf(Negative, "-0.", "0.") & _
                            Right$("0000" & Value, 4))
      Else
          TextToCurr = CCur(IIf(Negative, "-", "") & _
                            Left$(Value, L - 4) & "." & Right$(Value, 4))
      End If End Function
  
  ' Java Long as Currency Usage Example Dim LC As MungeCurr Dim L2 As Munge2Long
  
  ' Assign a Currency Value (really a Java Long)
  ' to the MungeCurr type variable LC.Value = cyTestIn
  
  ' Coerce the value to the Munge2Long type variable LSet L2 = LC
  
  ' Perform some operation on the value, now that we
  ' have it available in two 32-bit chunks L2.LoValue = L2.LoValue + 1
  
  ' Coerce the Munge value back into a currency value LSet LC = L2 cyTestIn = LC.Value
  

---

 

Related concepts

ActiveX to EJB Bridge

 

Related tasks

Develop ActiveX client application code

 

Related

ActiveX to Java primitive data type conversion values