firebase_google_login.js

import React, { Component } from 'react';
import {
  Text,
  View,
  TouchableOpacity,
  ActivityIndicator,
  Navigator
} from 'react-native';
import {GoogleSignin} from 'react-native-google-signin';
import Firestack from 'react-native-firestack'

const firestack = new Firestack({debug: true});

export default class Login extends Component {

  constructor(props) {
    super(props);
    this.state = {
      user: null,
      loading: false
    };
  }

  componentDidMount() {
    this.setupGoogleSignIn();
  }

  componentWillMount() {
  	console.log('a');
  }

  async setupGoogleSignIn() {
    try {
      this.setState({loading: true});
      await GoogleSignin.hasPlayServices({ autoResolve: true });
      await GoogleSignin.configure({
        iosClientId: '<IOS-CLIENTID>',
        webClientId: '<WEB-CLIENTID>',
        offlineAccess: true
      });

      GoogleSignin.currentUserAsync().then((user)=> {
      	if(user) {
      		console.log('GoogleUser ', user);
			    this.setState({loading: false, user: user});
      	} else {
      		this.setState({loading: false});
      	}
      });

      firestack.auth.listenForAuth((evt)=> {
        if (!evt.authenticated) {
            console.log(evt.error)
        } else {
          console.log('firebase user ', evt.user);
        }
      })
      .then(() => console.log('Listening for authentication changes'));

    }
    catch(err) {
      this.setState({loading: false});
      console.log("Google signin error", err.code, err.message);
    }
  }

  signIn() {
  	this.setState({loading: true});
    GoogleSignin.signIn()
      .then((user) => {
        this.setState({loading: false, user: user});
      }).catch((err) => {
        console.log('WRONG SIGNIN', err);
      })
      .done();
  }

  signOut() {
  	this.setState({loading: true});
    GoogleSignin.revokeAccess().then(() => GoogleSignin.signOut()).then(() => {
      this.setState({user: null, loading: false});
    })
    .done();
  }

  render() {
  	if(this.state.loading) {
  		return (
  			<View>
	  			<ActivityIndicator
		        	animating={true}
		        	style={{height: 80}}
		        	size="large"
		      	/>
		    </View>
	    );
  	} else {
  		if (!this.state.user) {
	      return (
	        <View>
	        <TouchableOpacity onPress={this.signIn.bind(this)} >
            <Text>Login</Text>
          </TouchableOpacity>
	        </View>
	      );
	    }
	    else {
        firestack.signInWithProvider('google', this.state.user.idToken).then((userFirebase)=>{
              console.log(userFirebase)

            }).catch((error)=> {
              console.log(error.error)
             });
             console.log('logged in user ', this.state.user);
	       return (
	        	<Text>{this.state.user.displayName}</Text>
	      	);
	    }
  	}
  }
}