Is it fine to create a separate interface for call back function in MVP pattern

Question

I am trying to create an app by using MVP design pattern. This is the first time i am using this pattern, thats the reason i am little concerned that either i am following the pattern correctly or not.

This is what i have done so far. I am not using Dagger2.

Interface

public interface MainActivityMVP {

    interface Model{
        void sendTokenToServer(MainActivityMVP.Presenter presenter);
    }

    interface View{
        boolean isPnTokenRegistered();
        void tokenUpdated();
        void tokenFailedToUpdate();
    }

    interface Presenter{
        void tokenUpdatedSuccessfully();
        void tokenAlreadyExists();
        void detachView();
    }

On MainActivity, I have created an instance of Presenter and Model and pass the Model object to Presenter Constructor

MainActivity

    public class MainActivity extends BaseActivity implements MainActivityMVP.View {

        @Override
        protected void onCreate(Bundle savedInstanceState) {
            super.onCreate(savedInstanceState);
            setContentView(R.layout.activity_base);

            mainPresenter= new MainPresenter(this, new MainModel());
            mainPresenter.sendFCMTokenToServer();
        }

On Presenter I call Model's method to perform operation, and pass presenter reference to it.

Presenter

    public class MainPresenter implements MainActivityMVP.Presenter{

        MainActivityMVP.View view;
        MainActivityMVP.Model model;


        public MainPresenter(MainActivityMVP.View view, MainActivityMVP.Model model){
            this.view= view;
            this.model= model;
        }


        public void sendFCMTokenToServer() {
            model.sendTokenToServer(this);
        }

       @Override
       public void tokenUpdatedSuccessfully() {
         view.tokenUpdated();
       }

        @Override
        public void tokenAlreadyExists() {
          view.tokenFailedToUpdate();
        }

In Model, I create instance of PreferenceManager class that gets data from SharedPreference

public class MainModel implements MainActivityMVP.Model {

    PreferencesHelper preferencesHelper;


    public MainModel(){
        preferencesHelper= new PreferencesHelper();
    }

 @Override
    public void sendTokenToServer(MainActivityMVP.Presenter presenter) {

        if (preferencesHelper.getNotificationSettings().isEmpty()) {
           //do stuff

           presenter.tokenUpdatedSuccessfully();
        }
  }

Now i have these questions.

• Is the above approach of implementing MVP pattern is fine, or i am missing something here.

• Is it fine if i add an other interface for call backs, or passing Presenter to model is better approach, as i have seen some example where they pass interactor reference to model.

• Is it necessary to create Interactor Class in MVP pattern

• Is it fine, and not against MVP rule if i create a separate interface for Repository,

Answer 1

Developers have different varieties of implementing MVP. Few people use interactors. Its is not compulsory to use interactors in MVP. I will suggest you below since you are in a starting stage.

 public interface MainView extends BaseView {
         boolean isPnTokenRegistered();
         void tokenUpdated();
         void tokenFailedToUpdate(); 
}

Then have your basepresenter be like this

public interface BasePresenter<V extends BaseView> {

    void setView(V view);

    void destroyView();

    void destroy();
}

Now your MainPresenter

    public class MainPresenter implements BasePresenter<MainView>{

    MainView view;
    PreferencesHelper preferencesHelper;

   MainPresenter(){
        preferencesHelper= new PreferencesHelper();
   }

      @Override
      public void setView(MainView view) {
        this.view = view;
      }

      @Override
      public void destroyView() {
        this.view = null;
      }

      @Override
      public void destroy() {

      }

       public void sendFCMTokenToServer() {
            //Do whatever you want
        }

    }

Finally have your activity like this,

public class MainActivity extends BaseActivity implements MainView {

        MainPresenter mainPresenter;

        @Override
        protected void onCreate(Bundle savedInstanceState) {
            super.onCreate(savedInstanceState);
            setContentView(R.layout.activity_base);
            mainPresenter= new MainPresenter();
            mainPresenter.attachView(this)
            mainPresenter.sendFCMTokenToServer();

        }