How to definition proto file to support listener parameter?

If I want to definition proto file for followings

main.cpp
      MyLib myLib;
      MyAdapter::Create(){
         myLib.create(this);
      }

      MyAdapter::OnInitialized(int result){
         std::cout << "result:" << result << std::endl;
      }
      ...
    }


myLib.cpp(=libmy.so)
    void My::create(ICreatorListener *listener);

ICreatorListener.h
    class ICreatorListener{
       public:
          virtual void OnInitialized(int result) = 0;
    }

My purpose is to exchange myLib's interface using google protobuf. Because I want to use mylib in c++ or java in universally. But I am not friendly google protobuf yet.

Question) Do I need define mylib.proto like followings? if so, how do I define for ICreatorListener *listener in mylib.proto? callback method is not supported in google protobuf?

MyLib.proto
message Result {
   int value = 1;
}

main.cpp
    MyAdapter::OnInitialized(const char* result){
         int resultVal = getValueFromGoogleProtoBuf(result);
         std::cout << "result:" << resultVal << std::endl;
    }

ICreatorListener.h
    class ICreatorListener{
       public:
          virtual void OnInitialized(const char* result) = 0;
    }