jre lib ext - Page 54 - Developer IT

Can I someone point to me what I did wrong? Trying to map VB to Java using JNA to access the library

- by henry

Original Working VB_Code Private Declare Function ConnectReader Lib "rfidhid.dll" () As Integer Private Declare Function DisconnectReader Lib "rfidhid.dll" () As Integer Private Declare Function SetAntenna Lib "rfidhid.dll" (ByVal mode As Integer) As Integer Private Declare Function Inventory Lib "rfidhid.dll" (ByRef tagdata As Byte, ByVal mode As Integer, ByRef taglen As Integer) As Integer Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load Dim desc As String desc = "1. Click ""Connect"" to talk to reader." & vbCr & vbCr desc &= "2. Click ""RF On"" to wake up the TAG." & vbCr & vbCr desc &= "3. Click ""Read Tag"" to get tag PCEPC." lblDesc.Text = desc End Sub Private Sub cmdConnect_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles cmdConnect.Click If cmdConnect.Text = "Connect" Then If ConnectReader() Then cmdConnect.Text = "Disconnect" Else MsgBox("Unable to connect to RFID Reader. Please check reader connection.") End If Else If DisconnectReader() Then cmdConnect.Text = "Connect" End If End If End Sub Private Sub cmdRF_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles cmdRF.Click If cmdRF.Text = "RF On" Then If SetAntenna(&HFF) Then cmdRF.Text = "RF Off" End If Else If SetAntenna(&H0) Then cmdRF.Text = "RF On" End If End If End Sub Private Sub cmdReadTag_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles cmdReadTag.Click Dim tagdata(64) As Byte Dim taglen As Integer, cnt As Integer Dim pcepc As String pcepc = "" If Inventory(tagdata(0), 1, taglen) Then For cnt = 0 To taglen - 1 pcepc &= tagdata(cnt).ToString("X2") Next txtPCEPC.Text = pcepc Else txtPCEPC.Text = "ReadError" End If End Sub Java Code (Simplified) import com.sun.jna.Library; import com.sun.jna.Native; public class HelloWorld { public interface MyLibrary extends Library { public int ConnectReader(); public int SetAntenna (int mode); public int Inventory (byte tagdata, int mode, int taglen); } public static void main(String[] args) { MyLibrary lib = (MyLibrary) Native.loadLibrary("rfidhid", MyLibrary.class); System.out.println(lib.ConnectReader()); System.out.println(lib.SetAntenna(255)); byte[] tagdata = new byte[64]; int taglen = 0; int cnt; String pcepc; pcepc = ""; if (lib.Inventory(tagdata[0], 1, taglen) == 1) { for (cnt = 0; cnt < taglen; cnt++) pcepc += String.valueOf(tagdata[cnt]); } } } The error happens when lib.Inventory is run. lib.Inventory is used to get the tag from the RFID reader. If there is no tag, no error. The error code An unexpected error has been detected by Java Runtime Environment: EXCEPTION_ACCESS_VIOLATION (0xc0000005) at pc=0x0b1d41ab, pid=5744, tid=4584 Java VM: Java HotSpot(TM) Client VM (11.2-b01 mixed mode windows-x86) Problematic frame: C [rfidhid.dll+0x141ab] An error report file with more information is saved as: C:\eclipse\workspace\FelmiReader\hs_err_pid5744.log

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