public class NewProductPresenter implements NewProductContract.Presenter,
      NewProductContract.Model.OnAddProductListener, NewProductContract.Model.OnModifyProductListener {

  private NewProductModel model;
  private NewProductView view;

  public NewProductPresenter(NewProductView view) {
    this.view = view;
    model = new NewProductModel(view.getApplicationContext());
  }

  @Override
  public void addProduct(String name, String category, String quantity, String price, boolean important, byte[] productImage) {
    if (!validData(name, category, quantity, price, important, productImage))
      view.showMessage("Error al validar la información");

    Product product = new Product(name, category, Integer.parseInt(quantity),
                      Float.parseFloat(price), important, productImage);
    model.addProduct(product, this);
  }

  @Override
  public void onAddProductSuccess(Product product) {
    view.showMessage("ok");
  }

  @Override
  public void onAddProductError(String message) {
    view.showMessage("error");
  }
  . . .
  . . .