How to create callbacks between android code and native code?

Question

I have a requirement for creating call backs between native code ( c language code) and Android code . I wrote JNI functions for calling C code from the android like this

JNI code here

#include <android/log.h>

void initSocket(); 

#ifdef __cplusplus
extern "C" {
#endif

  JNIEXPORT void JNICALL Java_org_pjsip_pjsua_pjsua_1appJNI_initSocket(JNIEnv *jenv, jclass jcls) {

    __android_log_write(ANDROID_LOG_INFO, " JNI CODE ", " APP INIT SOCKET");        
    initSocket();        
  }
}

C code looks like this

void initSocket()
{
    /// some more stuff
    printf("  initSocket function ");           
}

static int worker_thread(void *unused)
{       
    /// some more stuff
    return 0;
}

pj_bool_t on_rx_data1(pj_stun_sock *stun_sock, void *pkt, unsigned pkt_len, const pj_sockaddr_t *src_addr, unsigned addr_len)
{      
    /// some more stuff    
    return PJ_TRUE;
}

pj_bool_t on_data_sent1 (pj_stun_sock *stun_sock, pj_ioqueue_op_key_t *send_key, pj_ssize_t sent)
{        
    /// some more stuff
    return PJ_TRUE;  
}
pj_bool_t on_status1(pj_stun_sock *stun_sock, pj_stun_sock_op op, pj_status_t status)
{        
    /// some more stuff
    returnsockaddress();            
    return PJ_TRUE;
}

char* returnsockaddress()
{     
    /// some more stuff   
    return ipinttostring(sock_address);
}

char* ipinttostring(unsigned int addr )
{       
    /// some more stuff
    return fullIP;
}

this is the code i am using in C language, calling initSocket() function from JNI. Now i want to create a callback from this C code when on_status1 function called in this code. this on_status1 will repeat in few seconds when ever it's called i want to call a function in android code.

EDIT

I tried like this, but not succeeded

JNIEXPORT void JNICALL Java_org_pjsip_pjsua_pjsua_1appJNI_initSocket(JNIEnv *jenv, jobject obj) {

      __android_log_write(ANDROID_LOG_INFO, " JNI CODE ", " APP INIT SOCKET");            
      initSocket();             
      jclass cls = jenv->GetObjectClass(obj);
      jmethodID methodid = env->GetMethodID(cls, "callback", "()V");            
      if(!methodid) {
          return;
      }            
      jenv->CallVoidMethod(obj , methodid);            
  }

I was declared function like this in android code.

public static void callback(String value) {
    Log.e(TAG, "value:" + value);
}

Answer 1

Try this :

JNIEXPORT void JNICALL Java_org_pjsip_pjsua_pjsua_1appJNI_initSocket(JNIEnv *jenv, jobject obj) {
  __android_log_write(ANDROID_LOG_INFO, " JNI CODE ", " APP INIT SOCKET");            
  initSocket();             
  // jclass cls = (*jenv)->GetObjectClass(jenv, obj);
  // or something like this :
  jclass cls = (*jenv)->FindClass(jenv, "org/pjsip/pjsua/pjsua_appJNI"); 
  jmethodID methodid = (*jenv)->GetStaticMethodID(jenv, cls, "callback", "(Ljava/lang/String;)V");            
  if(!methodid) {
      return;
  }       
  jstring jstr = (*jenv)->NewStringUTF(jenv, "Hello from C"); 
  (*jenv)->CallStaticVoidMethod(jenv, cls, methodid, jstr); 
  }