Question

jni 返回java对象有什么需要注意的地方

Answer 1

JNIEXPORT jobject JNICALL Java_com_example_filltriangle_GL2JNILib_test(JNIEnv* env, jclass tis)  
    {  
        jclass m_login_msg = env->FindClass("hzcw/msgdata/LoginMsg");  
        jmethodID m_method_login_msg_init = env->GetMethodID(m_login_msg,"<init>","()V");  
        jobject m_login_msg_obj = env->NewObject(m_login_msg, m_method_login_msg_init);  
        jfieldID  m_fid_controlDictionary = env->GetFieldID(m_login_msg,"controlDictionary","Ljava/util/HashMap;");  
  
        // new一个hashmap对象  
        jclass class_hashmap=env->FindClass("java/util/HashMap");  
        jmethodID hashmap_construct_method=env->GetMethodID(class_hashmap, "<init>","()V");  
        jobject obj_hashmap =env->NewObject(class_hashmap, hashmap_construct_method, "");  
        jmethodID hashmap_put_method= env->GetMethodID(class_hashmap,"put","(Ljava/lang/Object;Ljava/lang/Object;)Ljava/lang/Object;");  
  
        // new一个ArrayList对象  
        jclass class_arraylist=env->FindClass("java/util/ArrayList");  
        jmethodID arraylist_construct_method=env->GetMethodID(class_arraylist, "<init>","()V");  
        jobject obj_arraylist =env->NewObject(class_arraylist, arraylist_construct_method, "");  
        jmethodID arraylist_add_method= env->GetMethodID(class_arraylist,"add","(Ljava/lang/Object;)Z");  
  
        // new一个ControlDictionaryValue对象  
        jclass m_cls_ControlDictionaryValue = env->FindClass("hzcw/datastruct/ControlDictionaryValue");  
        jmethodID m_mid_ControlDictionaryValue = env->GetMethodID(m_cls_ControlDictionaryValue,"<init>","()V");  
        jobject m_obj_ControlDictionaryValue = env->NewObject(m_cls_ControlDictionaryValue, m_mid_ControlDictionaryValue, "");  
        // 获取ControlDictionaryValue对象的value变量  
        jfieldID  m_fid_ControlDictionaryValue_value = env->GetFieldID(m_cls_ControlDictionaryValue,"value","Ljava/lang/String;");  
        env->SetObjectField(m_obj_ControlDictionaryValue,m_fid_ControlDictionaryValue_value,env->NewStringUTF("牙科"));  
  
        env->CallBooleanMethod(obj_arraylist, arraylist_add_method, m_obj_ControlDictionaryValue);  
  
        env->CallObjectMethod(obj_hashmap,hashmap_put_method,env->NewStringUTF((char*)"科室"), obj_arraylist);  
  
        env->SetObjectField(m_login_msg_obj,m_fid_controlDictionary,obj_hashmap);  
  
        env->DeleteLocalRef(m_obj_ControlDictionaryValue);  //删除局部引用  
        env->DeleteLocalRef(obj_arraylist);  //删除局部引用  
        env->DeleteLocalRef(obj_hashmap);  //删除局部引用  
  
        return m_login_msg_obj;  
    }