Location.js

import React from "react";
import { View, Text, Platform } from "react-native";
import { Constants, Location, Permissions } from "expo";

class PermissionsExample extends React.Component {
  state = {
    message: null,
    location: null
  };
  
  async componentWillMount() {
    try {
      if (Platform.OS === 'android' && !Constants.isDevice) {
        this.setState({ message: "This doesn't work on Android simulator!" });
        return;
      }
      
      const { status } = await Permissions.askAsync(Permissions.LOCATION);
      if (status !== "granted") {
        this.setState({ message: "Location permission was NOT granted!" });
        return;
      }
      
      const location = await Location.getCurrentPositionAsync({});
      this.setState({ location });
    } catch (err) {
      console.log(err);
    }
  }
  
  render() {
    let text = "Fetching location";
    const { message, location } = this.state;
    if (message !== null) {
      text = message;
    } else {
      text = JSON.stringify(location);
    }
    
    return (
      <View>
        <Text>{text}</Text>
      </View>
    );
  }
};