yokutango-mobile-reader/lib/screens/home.dart

import 'dart:convert';
import 'dart:io';

import 'package:tangocard_reader/models/yokutango_entry.dart';
import 'package:tangocard_reader/screens/error.dart';
import 'package:tangocard_reader/screens/loading.dart';
import 'package:flutter/material.dart';
import 'package:flutter/services.dart';

class Home extends StatelessWidget {
  const Home({Key? key}) : super(key: key);

  @override
  Widget build(BuildContext context) {
    return Scaffold(
        appBar: AppBar(
          title: const Text("よく単語"),
          centerTitle: true,
        ),
        body: const TangocardList());
  }
}

class TangocardList extends StatelessWidget {
  const TangocardList({Key? key}) : super(key: key);

  Future<Map<File, List<YokutangoEntry>>> get tangocardFilePaths => rootBundle
      .loadString('AssetManifest.json')
      .then(
        (json) => jsonDecode(json)
            .keys
            .where((String key) =>
                key.contains('yokutango/json/') && key.contains('.json'))
            .toList(),
      )
      .then(
        (l) async => Map.fromIterables(
          l.map<File>((f) => File(f)),
          await Future.wait<List<YokutangoEntry>>(
            l
                .map<Future<List<YokutangoEntry>>>(
                  (String t) => rootBundle
                      .loadString(t)
                      .then<List<YokutangoEntry>>((s) => jsonDecode(s)
                          .map<YokutangoEntry>(
                              (e) => YokutangoEntry.fromJson(e))
                          .toList()),
                )
          ),
        ),
      );

  @override
  Widget build(BuildContext context) {
    return FutureBuilder(
      future: tangocardFilePaths,
      builder: (context, snapshot) {
        if (snapshot.hasError) {
          debugPrint(snapshot.error.toString());
          return const ErrorScreen();
        } else if (!snapshot.hasData) {
          return const LoadingScreen();
        }

        return ListView(
          children: (snapshot.data as Map<File, List<YokutangoEntry>>)
              .entries
              .map(
                (e) => ListTile(
                  title: Text(
                      "${e.key.uri.pathSegments.last} - ${e.value.length} cards"),
                  onTap: () => Navigator.pushNamed(context, '/tangolist',
                      arguments: e.key),
                ),
              )
              .toList(),
        );
      },
    );
  }
}