Flutter - HTTP Request

main.dart

import 'dart:convert';

import 'package:flutter/material.dart';
import 'package:http/http.dart' as http;

void main() {
  runApp(MyApp());
}

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      theme: ThemeData(
        primarySwatch: Colors.blue,
        visualDensity: VisualDensity.adaptivePlatformDensity,
      ),
      home: MyHomePage(title: 'Flutter Demo Home Page'),
    );
  }
}

class MyHomePage extends StatefulWidget {
  MyHomePage({Key key, this.title}) : super(key: key);
  final String title;

  @override
  _MyHomePageState createState() => _MyHomePageState();
}

class _MyHomePageState extends State<MyHomePage> {
  final TextEditingController _controller = TextEditingController();
  Future<Response> futureResponse;
  Future<Response> _futureResponse;

  @override
  void initState() {
    super.initState();
    futureResponse = fetchText();
  }

  Future<Response> fetchText() async {
    final response = await http.get('http://localhost:8080');

    if (response.statusCode == 200) {
      return Response.fromJson(json.decode(response.body));
    } else {
      throw Exception('Failed to load album');
    }
  }

  Future<Response> updateText(String text) async {
    final http.Response response = await http.post(
      'http://localhost:8080/post',
      headers: <String, String>{
        'Content-Type': 'application/json; charset=UTF-8',
      },
      body: jsonEncode(<String, String>{
        'text': text,
      }),
    );
    if (response.statusCode == 200) {
      return Response.fromJson(json.decode(response.body));
    } else {
      throw Exception('Failed to load text');
    }
  }

  FutureBuilder<Response> buildFuture() {
    return FutureBuilder<Response>(
      future: (_futureResponse == null) ? futureResponse : _futureResponse,
      builder: (context, snapshot) {
        if (snapshot.hasData) {
          return Text(snapshot.data.text);
        } else if (snapshot.hasError) {
          return Text("${snapshot.error}");
        }
        return CircularProgressIndicator();
      },
    );
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text(widget.title),
      ),
      body: Padding(
        padding: const EdgeInsets.all(16.0),
        child: Center(
          child: Column(
            mainAxisAlignment: MainAxisAlignment.center,
            children: <Widget>[
              buildFuture(),
              TextField(
                controller: _controller,
              ),
              RaisedButton(
                child: Text("Update Text"),
                onPressed: () {
                  setState(() {
                    _futureResponse = updateText(_controller.text);
                  });
                },
              ),
            ],
          ),
        ),
      ),
    );
  }
}

class Response {
  final String text;

  Response({this.text});

  factory Response.fromJson(Map<String, dynamic> json) {
    return Response(
      text: json['text'],
    );
  }
}