Question

I’m new in Android JNI. I’m sending JAVA object from my java file to C code given below. My jObject info contains char[] values in java.Actually i think I’m unable to convert jObject to char and therefore when i compile this code i get the error:

warning: initialization makes integer from pointer without a cast

My C File :

typedef struct {
    unsigned char reg_chal[32];
    unsigned char aid[32];
} reg_info_t;

JNIEXPORT jint JNICALL Java_com_marakana_NativeLib_reg(JNIEnv *env,jclass obj,jobject info ,jchar details,jchar reg_code)
{
    reg_info_t regInfo;
    jclass clazz;
    jfieldID fid;
    jmethodID mid;

    jint status =0; 

    LOGD("NDK:LC: [%s]", "JNI Function call started");
    LOGD("NDK:LC: [%s]", details);
    LOGD("NDK:LC: [%c]", reg_code);

    //GetInfo(entryInfo);   // fills in the entryInfo

    clazz = (*env)->GetObjectClass(env, info);
    if (0 == clazz)
    {
        printf("GetObjectClass returned 0\n");
        return(-1);
    }

    jchar reg_chal = (*env)->NewStringUTF(env,regInfo.reg_chal);
    fid = (*env)->GetFieldID(env,clazz,"reg_chal","Ljava/lang/String;");
    (*env)->SetObjectField(env,info,fid,reg_chal);
    LOGD("NDK:LC: [%c]", reg_chal);

    jchar aid = (*env)->NewStringUTF(env,regInfo.aid );
    fid = (*env)->GetFieldID(env,clazz,"aid ","Ljava/lang/String;");
    (*env)->SetCharField(env,info,fid,aid );
    LOGD("NDK:LC: [%c]", aid);


    //reg_step_1(info ,  details, reg_code);
    //status = reg_step_1(info ,  details, reg_code);
    return status; 

}

Please help me how to fix this error of conversion?

Answer 1

NewStringUTF doesn’t return a jchar; it returns a jstring, which is really just a synonym for jobject.

You should change jchar reg_chal to jstring reg_chal, and change jchar aid to jstring aid.