App.js

import React, { Component } from 'react';
import { FlatList, AppRegistry, ActivityIndicator, Text, View } from 'react-native';

export default class FetchExample extends Component {
    constructor(props){
        super(props);
        this.state ={ isLoading: true}
    }

    componentDidMount(){
        return fetch('https://facebook.github.io/react-native/movies.json')
            .then((response) => response.json())
            .then((responseJson) => {
                this.setState({
                    isLoading: false,
                    dataSource: responseJson.movies,
                }, function () {

                });
        })
            .catch((error) =>{
                console.error(error);
            });
    }

    render() {
        if(this.state.isLoading){
            return(
                <View style={{flex:1, padding: 20}}>
                    <ActivityIndicator/>
                </View>
            )
        }

        return(
            <View style={{flex:1, paddingTop:20}}>
                <FlatList
                    data={this.state.dataSource}
                    renderItem={({item}) => <Text>{item.title}, {item.releaseYear}</Text>}
                    keyExtractor={(item, index) => index}
                />
            </View>
        );
  }
}

AppRegistry.registerComponent('react-native-tutorial', () => FetchExample);