RxJava + MVP Signup Form Validation

BaseView.java

public interface BaseView {
}

Presenter.java

public interface Presenter<V extends BaseView> {

  void attachView(V mvpView);

  void detachView();
}

SignUpActivity.java

public class SignUpActivity extends Activity implements SignUpView {

  EditText firstName;
  EditText lastName;
  EditText email;
  EditText zipCode;
  EditText password;
  Button submitButton;

  SignUpPresenter presenter;

  @Override
  protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    presenter = new SignUpPresenterImpl(this);

    Observable<Boolean> firstNameObservable =
        RxTextView.afterTextChangeEvents(firstName).map(presenter.isFirstNameValid());

    Observable<Boolean> lastNameObservable =
        RxTextView.afterTextChangeEvents(lastName).map(presenter.isLastNameValid());

    Observable<Boolean> emailObservable =
        RxTextView.afterTextChangeEvents(email).map(presenter.isEmailValid());

    Observable<Boolean> zipCodeObservable =
        RxTextView.afterTextChangeEvents(zipCode).map(presenter.isZipCodeValid());

    Observable<Boolean> passwordObservable =
        RxTextView.afterTextChangeEvents(password).map(presenter.isPasswordValid());

    firstNameObservable.subscribe(presenter.updateFirstNameViewState());
    lastNameObservable.subscribe(presenter.updateLastNameViewState());
    emailObservable.subscribe(presenter.updateEmailViewState());
    zipCodeObservable.subscribe(presenter.updateZipCodeViewState());
    passwordObservable.subscribe(presenter.updatePasswordViewState());

    Observable.combineLatest(firstNameObservable, lastNameObservable, emailObservable,
        zipCodeObservable, passwordObservable, presenter.isFormValid())
        .subscribe(this::updateSubmitButtonViewState);
  }

  @Override
  public void showProgress() {

  }

  @Override
  public void hideProgress() {

  }

  @Override
  public void showFirstNameError(CharSequence error) {
    firstName.setError(error);
  }

  @Override
  public void showLastNameError(CharSequence error) {
    lastName.setError(error);
  }

  @Override
  public void showEmailError(CharSequence error) {
    email.setError(error);
  }

  @Override
  public void showZipCodeError(CharSequence error) {
    zipCode.setError(error);
  }

  @Override
  public void showPasswordError(CharSequence error) {
    password.setError(error);
  }

  @Override
  public void navigateToMainScreen() {

  }

  @Override
  public void updateSubmitButtonViewState(boolean enabled) {
    submitButton.setEnabled(enabled);
  }
}

SignUpPresenter.java

public interface SignUpPresenter extends Presenter<SignUpView> {

  Func1<TextViewAfterTextChangeEvent, Boolean> isFirstNameValid();

  Action1<Boolean> updateFirstNameViewState();

  Func1<TextViewAfterTextChangeEvent, Boolean> isLastNameValid();

  Action1<Boolean> updateLastNameViewState();

  Func1<TextViewAfterTextChangeEvent, Boolean> isEmailValid();

  Action1<Boolean> updateEmailViewState();

  Func1<TextViewAfterTextChangeEvent, Boolean> isZipCodeValid();

  Action1<Boolean> updateZipCodeViewState();

  Func1<TextViewAfterTextChangeEvent, Boolean> isPasswordValid();

  Action1<Boolean> updatePasswordViewState();

  Func5<Boolean, Boolean, Boolean, Boolean, Boolean, Boolean> isFormValid();
}

SignUpPresenterImpl.java

public class SignUpPresenterImpl implements SignUpPresenter {

  private SignUpView signUpView;
  private final Context context;

  public SignUpPresenterImpl(Context context) {
    this.context = context;
  }

  @Override
  public Func1<TextViewAfterTextChangeEvent, Boolean> isFirstNameValid() {
    return textViewAfterTextChangeEvent -> FIRST_NAME_VALIDITY_CHECK;
  }

  @Override
  public Action1<Boolean> updateFirstNameViewState() {
    return isValid -> {
      if (!isValid) {
        signUpView.showFirstNameError(context.getString(R.string.firstname_error));
      }
    };
  }

  @Override
  public Func1<TextViewAfterTextChangeEvent, Boolean> isLastNameValid() {
    return textViewAfterTextChangeEvent -> LAST_NAME_VALIDITY_CHECK;
  }

  @Override
  public Action1<Boolean> updateLastNameViewState() {
    return isValid -> {
      if (!isValid) {
        signUpView.showLastNameError(R.string.lastname_error);
      }
    };
  }

  @Override
  public Func1<TextViewAfterTextChangeEvent, Boolean> isEmailValid() {
    return textViewAfterTextChangeEvent -> EMAIL_VALIDITY_CHECK;
  }

  @Override
  public Action1<Boolean> updateEmailViewState() {
    return isValid -> {
      if (!isValid) {
        signUpView.showEmailError(R.string.email_error);
      }
    };
  }

  @Override
  public Func1<TextViewAfterTextChangeEvent, Boolean> isZipCodeValid() {
    return textViewAfterTextChangeEvent -> ZIPCODE_VALIDITY_CHECK;
  }

  @Override
  public Action1<Boolean> updateZipCodeViewState() {
    return isValid -> {
      if (!isValid) {
        signUpView.showZipCodeError(R.string.zipcode_error);
      }
    };
  }

  @Override
  public Func1<TextViewAfterTextChangeEvent, Boolean> isPasswordValid() {
    return textViewAfterTextChangeEvent -> PASSWORD_VALIDITY_CHECK;
  }

  @Override
  public Action1<Boolean> updatePasswordViewState() {
    return isValid -> {
      if (!isValid) {
        signUpView.showPasswordError(R.string.password_error);
      }
    };
  }

  @Override
  public Func5<Boolean, Boolean, Boolean, Boolean, Boolean, Boolean> isFormValid() {
    return (isFirsNameValid, isLastNameValid, isEmailValid, isZipCodeValid, isPasswordValid) ->
        isFirsNameValid
            && isLastNameValid
            && isEmailValid
            && isZipCodeValid
            && isPasswordValid;
  }

  @Override
  public void attachView(SignUpView mvpView) {
    signUpView = mvpView;
  }

  @Override
  public void detachView() {

  }
}

SignUpView.java

public interface SignUpView extends BaseView {

  void showProgress();

  void hideProgress();

  void showFirstNameError(CharSequence error);

  void showLastNameError(CharSequence error);

  void showEmailError(CharSequence error);

  void showZipCodeError(CharSequence error);

  void showPasswordError(CharSequence error);

  void updateSubmitButtonViewState(boolean enabled);

  void navigateToMainScreen();
}

cool but it leaks