App.js

import React from "react";
import { createAppContainer } from "react-navigation";
import Amplify, { Auth } from "aws-amplify";
import { createRootNavigator } from "./router";
import config from "./config";

Amplify.configure({
  Auth: {
    mandatorySignIn: true,
    region: config.AWS.cognito.REGION,
    userPoolId: config.AWS.cognito.USER_POOL_ID,
    identityPoolId: config.AWS.cognito.IDENTITY_POOL_ID,
    userPoolWebClientId: config.AWS.cognito.APP_CLIENT_ID
  }
});

class App extends React.Component {
  state = {
    isAuthenticated: false
  };

  async componentDidMount() {
    try {
      await Auth.currentSession();
      this.setState({ isAuthenticated: true });
    } catch (error) {
      if (error !== "No current user") {
        console.log(error);
      }
    }
  }

  render() {
    const RootNavigator = createRootNavigator(this.state.isAuthenticated);
    const AppContainer = createAppContainer(RootNavigator);

    return (
      <AppContainer />
    );
  }
}