ListViewWidgetAfter.dart

import 'package:flutter/material.dart';

class ListViewWidget extends StatefulWidget {
  @override
  _ListViewWidgetState createState() => _ListViewWidgetState();
}

class _ListViewWidgetState extends State<ListViewWidget> {
  Future<List<String>> _data;

  @override
  void initState() {
    super.initState();
    _data = HogeData().getHogeData();
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text('List'),
      ),
      floatingActionButton: FloatingActionButton(
        child: Icon(Icons.swap_vert),
        onPressed: () => _reload(),
      ),
      body: FutureBuilder<List<String>>(
          future: _data,
          builder: (context, snapshot) {
            switch (snapshot.connectionState) {
              case ConnectionState.none:
                break;
              case ConnectionState.active:
              case ConnectionState.waiting:
                return Center(child: SizedBox(height: 50.0, width: 50.0, child: CircularProgressIndicator()));
              case ConnectionState.done:
                if (snapshot.hasError) {
                  return Text('${snapshot.error}');
                }

                if (snapshot.hasData) {
                  return ListView.builder(
                    itemCount: snapshot.data.length,
                    itemBuilder: (context, index) => ListItem(snapshot.data[index]),
                  );
                }
            }
            return null;
          }),
    );
  }

  void _reload() {
    _data = HogeData().getHogeData();
    setState(() {}); // ★これ！
  }
}