Java Question Library and JniWrapper

Wal · Oct 25, 2015

I have made a Library with the Ndk and a Wrapper. The wrapper works with Eclipse, how can I use it at B4A?

Wrapper:

B4X:

#include <jni.h>
#include "./library/test.h"

extern "C" {
    JNIEXPORT jboolean JNICALL Java_de_wal_librarytest_MBJniClass_OpenPort(JNIEnv * env, jobject obj, jboolean usebool);
    JNIEXPORT jboolean JNICALL Java_de_wal_librarytest_MBJniClass_ClosePort(JNIEnv * env, jobject obj);
};

JNIEXPORT jboolean JNICALL Java_de_wal_librarytest_MBJniClass_OpenPort(JNIEnv * env, jobject obj, jboolean usebool)
{
    return OpenPort(usebool);
}

JNIEXPORT jboolean JNICALL Java_de_wal_librarytest_MBJniClass_ClosePort(JNIEnv * env, jobject obj)
{
    return ClosePort();
}

Class:

B4X:

package de.wal.librarytest;

public class MBJniClass {
      static {
         System.loadLibrary("testlibrary");
      }
     
      public static native boolean OpenPort(boolean usebool);
      public static native boolean ClosePort();
}

Eclipse-Example:

B4X:

package de.wal.librarytest;

import de.wal.librarytest.MBJniClass;

import android.app.Activity;
import android.os.Bundle;
import android.view.Menu;
import android.view.MenuItem;

public class MainActivity extends Activity {
     
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
       
        if (MBJniClass.OpenPort(true)) {
           int i = 1    
       }
    }

DonManfred · Oct 25, 2015

You need to wrote a wrapper which can be used in b4a.

Something like

B4X:

import de.wal.MBJniClass;
import anywheresoftware.b4a.AbsObjectWrapper;
import anywheresoftware.b4a.BA;
import anywheresoftware.b4a.BA.Hide;
import anywheresoftware.b4a.BA.ShortName;
import anywheresoftware.b4a.BA.Version;
import anywheresoftware.b4a.BA.Author;

@Version(1.00f)
@Author("...")
@ShortName("MBJni")
//@Permissions(values={"android.permission.INTERNET", "android.permission.ACCESS_NETWORK_STATE"})
//@Events(values={"onSigned(sign As Object)"})
//@DependsOn(values={"android-viewbadger"})
public class MBJniClassWrapper extends AbsObjectWrapper<MBJniClass> {
    private BA ba;
    private String eventName;
    public void Initialize(final BA ba, String EventName) {
        _initialize(ba, null, EventName);
    }
   
    @Hide
    public void _initialize(final BA ba, Object activityClass, String EventName) {
        this.eventName = EventName.toLowerCase(BA.cul);
        this.ba = ba;
        this.setObject(new MBJniClass());
     }
   
    public void ClosePort(){
        this.getObject().ClosePort();
    }
   
    public void ClosePort(boolean usebool){
        this.getObject().OpenPort(usebool);
    }
}

MaFu · Oct 27, 2015

If you use the library only with B4A then you can create the JNI wrapper itself B4A compatible (as in Don Manfreds example), in this case there is no need to create a wrapper for the wrapper.

Wal · Oct 28, 2015

it works, thank you

Wal · Oct 29, 2015

I have a problem with a call. What should be the Jniexport ?

C++ Code:

B4X:

char GetError(int *err)
{   
    DWORD dwBytes;
    unsigned char input[10]={0};
   
    if(!ReadSerialBytes(hSerial, input, 10,&dwBytes,true))
        return -1;

    if(dwBytes < 8)
        return -1;
       
    if(Header(input,dwBytes))
    {
        if (input[5]==0x01)
        {
            *err=0;
            return input[6];
        }
       
        if (input[5]==0x03)
        {
            if (input[6]>0)
            {
                *err=(0xFF & input[7]) << 8 |(0xFF & input[8]);       
                return 1;
            }
            else
                return 0;
        }
       
        return -1;
    }
    else
        return -1;
}

Jni :

B4X:

JNIEXPORT jbyte JNICALL Java_de_wal_library_MBLib_GetError(JNIEnv * env, jobject obj, jint err)
{
    return GetError(&err);
}

not correct

MaFu · Oct 29, 2015

What's the error message?

Wal · Oct 29, 2015

No error message, err is always 0 and not 66.
input[6] is the correct.

For testing, I use this code:

B4X:

if (input[5]==0x01)
        {
            *err=66;
            return input[6];
        }

Wal · Oct 29, 2015

Declare:

B4X:

_extern char GetError(int *err);

Informatix · Oct 29, 2015

Wal said:

I have a problem with a call. What should be the Jniexport ?

C++ Code:

B4X:

char GetError(int *err)
{  
    DWORD dwBytes;
    unsigned char input[10]={0};
  
    if(!ReadSerialBytes(hSerial, input, 10,&dwBytes,true))
        return -1;

    if(dwBytes < 8)
        return -1;
      
    if(Header(input,dwBytes))
    {
        if (input[5]==0x01)
        {
            *err=0;
            return input[6];
        }
      
        if (input[5]==0x03)
        {
            if (input[6]>0)
            {
                *err=(0xFF & input[7]) << 8 |(0xFF & input[8]);      
                return 1;
            }
            else
                return 0;
        }
      
        return -1;
    }
    else
        return -1;
}

Jni :

B4X:

JNIEXPORT jbyte JNICALL Java_de_wal_library_MBLib_GetError(JNIEnv * env, jobject obj, jint err)
{
    return GetError(&err);
}

not correct

When you export something to Java, it must be a JNI type or object. jchar is the JNI type corresponding to char.
http://docs.oracle.com/javase/7/docs/technotes/guides/jni/spec/types.html

Wal · Oct 29, 2015

Informatix said:
When you export something to Java, it must be a JNI type or object. jchar is the JNI type corresponding to char.
http://docs.oracle.com/javase/7/docs/technotes/guides/jni/spec/types.html

The value that is passed to Char is correct. The value that is passed to int *err, is not true.
B4A Code:

B4X:

Dim MB As MBLib
Value = MB.GetError(err)
labErr.Text = err  'not correct
labValue.Text = Value 'correct

Informatix · Oct 29, 2015

Wal said:
The value that is passed to Char is correct. The value that is passed to int *err, is not true.
B4A Code:

B4X:

Dim MB As MBLib Value = MB.GetError(err) labErr.Text = err 'not correct labValue.Text = Value 'correct

Pass a jint, not an int * (Java does not handle pointers).

Wal · Oct 29, 2015

Ok,
i have rewrite the Jni:

B4X:

JNIEXPORT jintArray JNICALL Java_de_wal_library_MBLib_GetError(JNIEnv * env, jobject obj)
{
    jint value[2] = {};
    jint err;
    jintArray arr = env->NewIntArray(2);
    value[0] = GetError(&err);
    value[1] = err;
    env->SetIntArrayRegion(arr, 0, 2, value);
    return arr;
}

How should I declare the wrapper in B4A ?

B4X:

package de.wal.library;

import anywheresoftware.b4a.BA.ShortName;
import anywheresoftware.b4a.BA.Version;
import anywheresoftware.b4a.BA.Author;

@Version(1.00f)
@Author("Ich")
@ShortName("MBLib")

public class MBLib {
      static {
         System.loadLibrary("mblibrary");
      }
      public static native long CommVersion();
      public static native boolean OpenPort(String port, boolean usebool);
      public static native boolean ClosePort();
      public static native ????? GetError();
}

Wal · Oct 29, 2015

The solution is:

B4X:

public static native int[] GetError();

B4A:

B4X:

Dim Err(1) As Int
    Err = MB.GetError
    labErr.Text = Err(0)
    labValue.Text = Err(1)

Thank's

Wal · Oct 30, 2015

Next problem, how can I generate a Unicode string from a array of int.
Jni:

B4X:

public static native int[] GetProgramName();

B4A:

B4X:

Dim ProgramName(400) As Int

ProgramName = MB.GetProgramName

labProgamName.Text = ?????

Informatix · Oct 30, 2015

BytesToString(...)

Java Question Library and JniWrapper

Wal

Member

DonManfred

Expert

MaFu

Well-Known Member

Wal

Member

Wal

Member

MaFu

Well-Known Member

Wal

Member

Wal

Member

Informatix

Expert

Wal

Member

Informatix

Expert

Wal

Member

Wal

Member

Wal

Member

Informatix

Expert

Similar Threads

Java Question Library and JniWrapper

Member

Expert

Well-Known Member

Member

Member

Well-Known Member

Member

Member

Expert

Member

Expert

Member

Member

Member

Expert

Similar Threads

Privacy & Transparency

Privacy & Transparency