ao code from csipsimple

android_jni_dev.c

JavaVM *android_jvm;

JNIEXPORT jint JNI_OnLoad(JavaVM *vm, void *reserved)
{
    android_jvm = vm;
    
    return JNI_VERSION_1_4;
}

static pj_bool_t attach_jvm(JNIEnv **jni_env)
{
    if ((*android_jvm)->GetEnv(android_jvm, (void **)jni_env,
                               JNI_VERSION_1_4) < 0)
    {
        if ((*android_jvm)->AttachCurrentThread(android_jvm, jni_env, NULL) < 0)
        {
            jni_env = NULL;
            return PJ_FALSE;
        }
        return PJ_TRUE;
    }
    
    return PJ_FALSE;
}

#define detach_jvm(attached) \
    if (attached) \
        (*android_jvm)->DetachCurrentThread(android_jvm);

/* Thread priority utils */
/* TODO : port it to pj_thread functions */
#define THREAD_PRIORITY_AUDIO -16
#define THREAD_PRIORITY_URGENT_AUDIO -19

pj_status_t set_android_thread_priority(int priority)
{
    jclass process_class;
    jmethodID set_prio_method;
    jthrowable exc;
    pj_status_t result = PJ_SUCCESS;
    JNIEnv *jni_env = 0;
    pj_bool_t attached = attach_jvm(&jni_env);
    
    PJ_ASSERT_RETURN(jni_env, PJ_FALSE);

    /* Get pointer to the java class */
    process_class = (jclass)(*jni_env)->NewGlobalRef(jni_env, 
                        (*jni_env)->FindClass(jni_env, "android/os/Process"));
    if (process_class == 0) {
        PJ_LOG(4, (THIS_FILE, "Unable to find os process class"));
        result = PJ_EIGNORED;
        goto on_return;
    }
    
    /* Get the id of set thread priority function */
    set_prio_method = (*jni_env)->GetStaticMethodID(jni_env, process_class,
                                                    "setThreadPriority",
                                                    "(I)V");
    if (set_prio_method == 0) {
        PJ_LOG(4, (THIS_FILE, "Unable to find setThreadPriority() method"));
        result = PJ_EIGNORED;
        goto on_return;
    }
    
    /* Set the thread priority */
    (*jni_env)->CallStaticVoidMethod(jni_env, process_class, set_prio_method,
                                     priority);    
    exc = (*jni_env)->ExceptionOccurred(jni_env);
    if (exc) {
        (*jni_env)->ExceptionDescribe(jni_env);
        (*jni_env)->ExceptionClear(jni_env);
        PJ_LOG(4, (THIS_FILE, "Failure in setting thread priority using "
                              "Java API, fallback to setpriority()"));
        setpriority(PRIO_PROCESS, 0, priority);
    } else {
        PJ_LOG(4, (THIS_FILE, "Setting thread priority successful"));        
    }

on_return:
    detach_jvm(attached);
    return result;
}