App.js

import React, { Component } from "react";
import { StyleSheet, Text, View, Button, AsyncStorage } from "react-native";

import FetchLocation from "./components/FetchLocation";
import Login from "./components/Login";

export default class App extends React.Component {
  state = {
    userLocation: null
  };

  userTrackingHandler = () => {
    navigator.geolocation.getCurrentPosition(
      position => {
        this.setState({
          userLocation: {
            latitude: position.coords.latitude,
            longitude: position.coords.longitude,
            latitudeDelta: 0.0522,
            longitudeDelta: 0.0421
          }
        });
      },
      err => console.log(err)
    );
  };
  render() {
    return (
      <View style={styles.container}>
        <View style={{ flex: 1, flexDirection: "column" }}>
          <Login />
        </View>
      </View>
    );
  }
}

// <FetchLocation onStartTracking={this.userTrackingHandler} />

const styles = StyleSheet.create({
  container: {
    flex: 1,
    justifyContent: "center",
    alignItems: "center",
    backgroundColor: "#F5FCFF"
  },
  welcome: {
    fontSize: 40,
    textAlign: "center",
    margin: 10
  }
});