PersonModel.java

class PersonsModel {
  // In a real application fields would be private
  // and we would have getters to access them
  final boolean loading;
  final List<Person> persons;
  final Throwable error;

  public(boolean loading, List<Person> persons, Throwable error){
    this.loading = loading;
    this.persons = persons;
    this.error = error;
  }
  
  // ... getters ...
}

PersonsActivity.java

class PersonsActivity extends MviActivity<PersonsPresenter> implements PersonsView {
    
  private PersonsAdapter adatper;
  
  // ... other things like onCreate() etc.

  @Override public Observable<Boolean> load() {
    return Observable.just(true);
  }
  
  @Override public void render(PersonsModelWithDiff viewState){
      if (viewState.isLoading() ) {
        // Show Loading
        loadingView.setVisisbility(View.VISIBLIE)
        erroView.setVisibility(View.GONE);
        recyclerView.setVisibility(View.GONE);
      } else if (viewState.getError() != null) {
        // Show Error
        loadingView.setVisisbility(View.GONE)
        erroView.setVisibility(View.VISIBLE);
        recyclerView.setVisibility(View.GONE);
      } else if (viewState.getPersons() != null ){
        // Show Content (RecyclerView)
        adapter.setPersons(viewState.getPersons());
        viewState.getDiffResult().dispatchTo(adapter);
        
        loadingView.setVisisbility(View.GONE)
        erroView.setVisibility(View.GONE);
        recyclerView.setVisibility(View.VISIBLE);
      } else {
        throw new IllegalStateException("Don't know how to render "+viewState);
      }
  }
}

PersonsInteractor.java

// This class is responsible to load a list of persons from backend
class PersonsInteractor {
  private Backend backend;
  
   public Observable<PersonsModel> loadPersons(){
        return backend.getPersons() // Executes an http call i.e. with retrofit; returns Observable<List<Person>>
               .map( persons -> new PersonModel(false, persons, null) )
               .startWith( new PersonModel(true, null, null) )  // Indicates Loading
               .onErrorReturn( error -> new PersonModel(false, null, error) ); // Indicates Error
   }
}

PersonsModelWithDiff.java

class PersonsModelWithDiff {
  // In a real application fields would be private
  // and we would have getters to access them
  final boolean loading;
  final List<Person> persons;
  final DiffResult result;
  final Throwable error;

  public(PersonModel originalModel, DiffResult diffResult){
    this.loading = originalModel.getLoading();
    this.persons = originalModel.getPersons();
    this.error = originalModel.getError();
    this.diffResult = diffResult;
  }
  
  // ... getters ...
}

PersonsPresenter.java

class PersonsPresenter extends MviBasePresenter<PersonsView, PersonsModelWithDiff> {

  private final PersonsInteractor interactor;
  // This will interally hold a list to the previous List<Person>;
  // However, that means that the function using this callback is not pure anymore (because it is a sideeffect to hold internally previous List<Person>
  // To make it pure one could use RxJava scan operator.
  private final DiffUtil.Callback callback; 
  
  public void bindIntents(){
  
    Observable<PersonsModelWithDiff> observable = intent(PersonsView::load)
       .flatMap( ignored -> interactor.load() )
       .map( personModel -> {
         if (personModel.getPersons() != null)
            return new PersonsModelWithDiff(personModel, DiffUtils.calculateDiff(callback));
         else
            return new PersonsModelWithDiff(personModel, null);
       })
      .subscribeOn(Schedulers.io())
      .observeOn(AndroidSchedulers.mainThread());
    
    subscribeViewState(observable, PersonsView::render);
  }
}