App.js

/**
 * Sample React Native App
 * https://github.com/facebook/react-native
 *
 * @format
 * @flow
 */

import React, {Component} from 'react';
import {Platform, StyleSheet, Text, View} from 'react-native';
import Web3 from 'web3';

const instructions = Platform.select({
  ios: 'Press Cmd+R to reload,\n' + 'Cmd+D or shake for dev menu',
  android:
    'Double tap R on your keyboard to reload,\n' +
    'Shake or press menu button for dev menu',
});

const provider = Platform.select({
  ios: 'ws://localhost:8545',
  android: 'ws://10.0.2.2:8545'
});

type Props = {};
export default class App extends Component<Props> {
  state = {
    accounts: 'EMPTY'
  }
  
  componentWillMount() {
    this.web3  = new Web3(provider);
    this.web3.eth.getBlock('latest').then(console.log).catch(console.log);
    var that = this;
    this.web3.eth.getAccounts(function(error,res) {
      if(!error) {
        console.log(res);
        that.setState({
          accounts: JSON.stringify(res)
        })
      } else {
        console.log(error);
        that.setState({
          accounts: 'error'
        })
      }
    });
  }

  render() {
    return (
      <View style={styles.container}>
        <Text style={styles.welcome}>Welcome to React Native!</Text>
        <Text style={styles.instructions}>To get started, edit App.js</Text>
        <Text style={styles.instructions}>{instructions}</Text>
        <Text>{this.state.accounts}</Text>
      </View>
    );
  }
}

const styles = StyleSheet.create({
  container: {
    flex: 1,
    justifyContent: 'center',
    alignItems: 'center',
    backgroundColor: '#F5FCFF',
  },
  welcome: {
    fontSize: 20,
    textAlign: 'center',
    margin: 10,
  },
  instructions: {
    textAlign: 'center',
    color: '#333333',
    marginBottom: 5,
  },
});