From a tutorial, this simple app covers getting a JSON response from an HTTP get request and displaying the content in a scrolling ListView.

flutter_http_json_listview

/// NOTE: Need some yamspec.yml to complete from a default configuration.

import 'dart:convert';

import 'package:flutter/material.dart';

import 'package:http/http.dart' as http;
import 'dart:async';
import 'dart:io';

void main() {
  runApp(new MaterialApp(home: new MyApp()));
}

class MyApp extends StatefulWidget {
  @override
  _State createState() => new _State();
}

class _State extends State<MyApp> {
  Map _countries = new Map();

  void _getData() async {
    String url =   "http://country.io/names.json"; // as Uri;  //Uri.('http://country.io/names.json');
    var response = await http.get(Uri.parse(url));

    if (response.statusCode == 200) {
      setState(() => _countries = jsonDecode(response.body));
      var verbose = true;
      print('Loaded ${_countries.length} countries.');
    }
  }

  // This widget is the root of your application.
  @override
  Widget build(BuildContext context) {
    return Scaffold(
        appBar: AppBar(
          title: Text("Udemy List view"),
        ),
        body: new Container(
          padding: EdgeInsets.all(32.0),
          child: new Column(
            children: <Widget>[
              Text("${_countries.length} Countries"),
              new Expanded(
                  child: new ListView.builder(
                itemCount: _countries.length,
                itemBuilder: (BuildContext context, int index) {
                  String key = _countries.keys.elementAt(index);
                  return new Row(
                    children: <Widget>[
                      new Text("$key : "),
                      new Text(_countries[key])
                    ]
                  );
                },
              ))
            ],
          ),
        ));
  }

  @override
  void initState() {
    super.initState();
    _getData();
  }
}