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

void main() {
  return runApp(TestPage());
}

//リスト4.20
class TestPage extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'ListView',
      home: Scaffold(
        appBar: AppBar(title: Text('ListView')),
        body: HogeListWidget()
      )
    );
  }
}

class HogeListWidget extends StatefulWidget {
  @override
  State<HogeListWidget> createState() => _HogeListWidgetState();
}

class _HogeListWidgetState extends State<HogeListWidget> {
  ScrollController? _scrollController;

  @override
  void initState() {
    super.initState();
    _scrollController = ScrollController();
    _scrollController!.addListener(() {
      final positionRate = _scrollController!.offset
          / _scrollController!.position.maxScrollExtent;

      if (positionRate == 1.0) {
        ScaffoldMessenger.of(context).showSnackBar(
            SnackBar(content: const Text('1番下です')));
      }
    });
  }

  @override
  Widget build(BuildContext context) {
    return ListView(
      controller: _scrollController,
      children: List.generate(100, (i) => Text('Item$i')),
    );
  }

  @override
  void dispose() {
    _scrollController?.dispose();
    super.dispose();
  }
}