How to disable the back button on certain React Navigation routes with React Native

Hello, I'm working with React Navigation and I'm having problems with the "back" button on certain screens.

My navigator is as follows:

import React from 'react'
import { FluidNavigator } from 'react-navigation-fluid-transitions'

import SplashScreen from '../../screens/SplashScreen'
import LoginScreen from '../../screens/LoginScreen'
import RegisterCodeScreen from '../../screens/RegisterScreen/RegisterCodeScreen'
import RegisterEmailScreen from '../../screens/RegisterScreen/RegisterEmailScreen'
import RegisterInfoScreen from '../../screens/RegisterScreen/RegisterInfoScreen'
import LanScreen from '../../screens/LanScreen'

export default Navigator = FluidNavigator({
  SplashScreen: { screen: SplashScreen },
  LoginScreen: { screen: LoginScreen, },
  RegisterEmailScreen: { screen: RegisterEmailScreen },
  RegisterCodeScreen: { screen: RegisterCodeScreen },
  RegisterInfoScreen: { screen: RegisterInfoScreen },
  LanScreen: { screen: LanScreen }
});

I need to lock the "back" only on the LoginScreen and LanScreen screens, and for that (currently) I'm using the resource below:

export defaut class LoginScreen extends React.Component {

  componentDidMount() {
    BackHandler.addEventListener('hardwareBackPress', () => true);
  }

  // ....

}

The problem is that using BackHandler causes it to disable on all routes and I do not want this ... How to solve?