How to call Java function from jni

gistfile1.txt

1. Jni:
extern "C" JNIEXPORT void JNICALL
Java_com_example_javaactivity_initApplicationNative(
        JNIEnv* env, jobject obj)
{
    __android_log_print(ANDROID_LOG_VERBOSE, "jni", "jni initApplicationNative");
    env->GetJavaVM(&javaVM);
    jclass cls = env->GetObjectClass(obj);
    activityClass = (jclass) env->NewGlobalRef(cls);
    activityObj = env->NewGlobalRef(obj);
}

void startCamera(jint a,jint b, jint c)
{
    JNIEnv *env;
    javaVM->AttachCurrentThread(&env, NULL);
    jmethodID method = env->GetMethodID(activityClass, "jniCallReady", "(III)V");

    env->CallVoidMethod(activityObj, method,a,b,c);
}

2.Java:
initApplicationNative();//init interface in activity

define function:
public void jniCallReady(int a, int b, int c){
//do st
}