Hi , I have some problem to access the twain interface using a callback
function.

Here is the c-code for the function (Plattform is MS-Windows):

#ifdef _MSWIN_ TW_UINT16 FAR PASCAL DSM_Entry( pTW_IDENTITY pOrigin, pTW_IDENTITY pDest, TW_UINT32 DG, TW_UINT16 DAT, TW_UINT16 MSG, TW_MEMREF pData);

and my JNA interface: public interface Twain extends Library { public static interface DSM_Entry extends Callback { public int callback(TW_IDENTITY origin, //source of message TW_IDENTITY dest, //destination of message int dg, //data group ID: DG_xxxx short dat, //data argument type: DAT_xxxx short msg, //message ID: MSG_xxxx Structure data); //pointer to data (TW_MEMREF = LPVOID) }//end class DSM_Entry }//end interface Twain

The C-structure of the pTW_IDENTITY from twain.h:

/* DAT_IDENTITY. Identifies the program/library/code resource. */ typedef struct { TW_UINT32 Id; /* Unique number. In Windows, application hWnd
*/ TW_VERSION Version; /* Identifies the piece of code */ TW_UINT16 ProtocolMajor; /* Application and DS must set to
TWON_PROTOCOLMAJOR */ TW_UINT16 ProtocolMinor; /* Application and DS must set to
TWON_PROTOCOLMINOR */ TW_UINT32 SupportedGroups; /* Bit field OR combination of DG_ constants */ TW_STR32 Manufacturer; /* Manufacturer name, e.g. "Hewlett-Packard" */ TW_STR32 ProductFamily; /* Product family name, e.g. "ScanJet" */ TW_STR32 ProductName; /* Product name, e.g. "ScanJet Plus" */ } TW_IDENTITY, FAR * pTW_IDENTITY;

The java code I tried: public class TW_IDENTITY extends Structure { public int Id; // hWnd public TW_VERSION Version; // TW_VERSION public short ProtocolMajor; // TW_UINT16 public short ProtocolMinor; // TW_UINT16 public int SupportedGroups; // TW_UINT32 public String Manufacturer; // TW_STR32 public String Productfamily; public String ProductName; }//end class

The pData should be a pointer to the user interface: C: /* DAT_USERINTERFACE. Coordinates UI between application and data source. */ typedef struct { TW_BOOL ShowUI; /* TRUE if DS should bring up its UI */ TW_BOOL ModalUI; /* For Mac only - true if the DS's UI is modal */ TW_HANDLE hParent; /* For windows only - Application window handle */ } TW_USERINTERFACE, FAR * pTW_USERINTERFACE;

Java: public class TW_USERINTERFACE extends Structure { public boolean ShowUI; public boolean ModalUI; public Pointer hParent; } //end class TW_Userinterface

I tried this interface but got an Exception in thread "main"
java.lang.NullPointerException

For the sake of completeness the source of the main program: import com.sun.jna.*; import image.twain.*;

public class JCam {

public interface Twain extends Library { public static interface DSM_Entry extends Callback { public int callback(TW_IDENTITY origin, //source of message TW_IDENTITY dest, //destination of message int dg, //data group ID: DG_xxxx short dat, //data argument type: DAT_xxxx short msg, //message ID: MSG_xxxx Structure data); //pointer to data (TW_MEMREF = LPVOID) }//end class DSM_Entry }//end interface Twain

public static Twain.DSM_Entry dsm_entry; public static TW_IDENTITY origin = new TW_IDENTITY(); public static TW_USERINTERFACE ui = new TW_USERINTERFACE();

public static void main(String[] args) { // Twain twain = (Twain) Native.loadLibrary("twain_32", Twain.class);

//Definition of Origin origin.Id = 0; //null; origin.Version.MajorNum = 0; origin.Version.MinorNum = 1; origin.Version.Language = TWAIN.TWLG_GER; origin.Version.Country = TWAIN.TWCY_GERMANY; origin.Version.Info = "JCam 0.1";

origin.ProtocolMajor = TWAIN.TWON_PROTOCOLMAJOR; origin.ProtocolMinor = TWAIN.TWON_PROTOCOLMINOR; origin.SupportedGroups = TWAIN.DG_CONTROL | TWAIN.DG_IMAGE; origin.Manufacturer = "Hans-Guenter Krull"; origin.Productfamily = "Java based image capture"; origin.ProductName = "JCam";

int test = dsm_entry.callback(origin, (TW_IDENTITY) null, TWAIN.DG_CONTROL, TWAIN.DAT_USERINTERFACE, TWAIN.MSG_ENABLEDS, ui); } } //end of class

Sorry for the stupid question

Hans