public class NewProductView extends AppCompatActivity implements NewProductContract.View {

  private int SELECT_PICTURE_RESULT = 1;
  private NewProductPresenter presenter;
  private Action action;
  private Product product;

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

    // Tenemos una enumeración definida para saber si tenemos que Registrar o Modificar un producto
    // Eso nos permite reutilizar el formulario que usamos para la recogida de datos
    action = Action.valueOf(getIntent().getStringExtra("ACTION"));
    if (action == PUT) {
      product = getIntent().getParcelableExtra("product");
      fillProductDetails();    // TODO No está hecho para este ejemplo
    }

    presenter = new NewProductPresenter(this);
  }

  public void addProduct(View view) {
    EditText etName = findViewById(R.id.product_name);
    EditText etCategory = findViewById(R.id.product_category);
    EditText etQuantity = findViewById(R.id.product_quantity);
    EditText etPrice = findViewById(R.id.product_price);
    CheckBox checkImportant = findViewById(R.id.important_product);
    ImageView productImageView = findViewById(R.id.product_image);

    String name = etName.getText().toString();
    String category = etCategory.getText().toString();
    String quantity = etQuantity.getText().toString();
    String price = etPrice.getText().toString();
    boolean important = checkImportant.isChecked();
    byte[] productImage = ImageUtils.fromImageViewToByteArray(productImageView);

    if (action == POST)
      presenter.addProduct(name, category, quantity, price, important, productImage);
    else
      presenter.modifyProduct(product.getId(), name, category, quantity, price, important, productImage);

    etName.setText("");
    etCategory.setText("");
    etQuantity.setText("");
    etPrice.setText("");
    checkImportant.setChecked(false);
    etName.requestFocus();
  }

  @Override
  public void showMessage(String message) {
    Toast.makeText(this, message, Toast.LENGTH_SHORT).show();
  }

  public void selectPicture(View view) {
    Intent intent = new Intent(Intent.ACTION_PICK, android.provider.MediaStore.Images.Media.EXTERNAL_CONTENT_URI);
    startActivityForResult(intent, SELECT_PICTURE_RESULT);
  }

  @Override
  protected void onActivityResult(int requestCode, int resultCode, Intent data) {
    super.onActivityResult(requestCode, resultCode, data);
    if ((requestCode == SELECT_PICTURE_RESULT) && (resultCode == RESULT_OK)
                                               && (data != null)) {
       Picasso.get().load(data.getData())
                    .noPlaceholder()
                    .centerCrop()
                    .fit()
                    .into((ImageView) findViewById(R.id.product_image));
    }
  }
  . . .
  . . .
}