lib/photo_list_screen.dart

import 'dart:io';

import 'package:file_picker/file_picker.dart';
import 'package:firebase_auth/firebase_auth.dart';
import 'package:flutter/material.dart';
import 'package:flutter_riverpod/flutter_riverpod.dart';
import 'package:photoapp/photo.dart';
import 'package:photoapp/photo_repository.dart';
import 'package:photoapp/photo_view_screen.dart';
import 'package:photoapp/providers.dart';
import 'package:photoapp/sign_in_screen.dart';

class PhotoListScreen extends StatefulWidget {
  @override
  _PhotoListScreenState createState() => _PhotoListScreenState();
}

class _PhotoListScreenState extends State<PhotoListScreen> {
  late PageController _controller;

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

    _controller = PageController(
      // Riverpodを使いデータを受け取る
      initialPage: context.read(photoListIndexProvider).state,
    );
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      // ...
      body: PageView(
        controller: _controller,
        onPageChanged: (int index) => _onPageChanged(index),
        children: [
          // 「全ての画像」を表示する部分
          Consumer(builder: (context, watch, child) {
            // 画像データ一覧を受け取る
            final asyncPhotoList = watch(photoListProvider);
            return asyncPhotoList.when(
              data: (List<Photo> photoList) {
                return PhotoGridView(
                  photoList: photoList,
                  onTap: (photo) => _onTapPhoto(photo, photoList),
                );
              },
              loading: () {
                return Center(
                  child: CircularProgressIndicator(),
                );
              },
              error: (e, stackTrace) {
                return Center(
                  child: Text(e.toString()),
                );
              },
            );
          }),
          //「お気に入り登録した画像」を表示する部分
          Consumer(builder: (context, watch, child) {
            // 画像データ一覧を受け取る
            final asyncPhotoList = watch(photoListProvider);
            return asyncPhotoList.when(
              data: (List<Photo> photoList) {
                return PhotoGridView(
                  photoList: photoList,
                  onTap: (photo) => _onTapPhoto(photo, photoList),
                );
              },
              loading: () {
                return Center(
                  child: CircularProgressIndicator(),
                );
              },
              error: (e, stackTrace) {
                return Center(
                  child: Text(e.toString()),
                );
              },
            );
          }),
        ],
      ),
      // ...
      bottomNavigationBar: Consumer(
        builder: (context, watch, child) {
          // 現在のページを受け取る
          final photoIndex = watch(photoListIndexProvider).state;

          return BottomNavigationBar(
            // ...
          );
        },
      ),
    );
  }

  void _onPageChanged(int index) {
    // ページの値を更新する
    context.read(photoListIndexProvider).state = index;
  }

  void _onTapBottomNavigationItem(int index) {
    _controller.animateToPage(
      index,
      duration: Duration(milliseconds: 300),
      curve: Curves.easeIn,
    );
    // ページの値を更新する
    context.read(photoListIndexProvider).state = index;
  }

  void _onTapPhoto(Photo photo, List<Photo> photoList) {
    final initialIndex = photoList.indexOf(photo);

    Navigator.of(context).push(
      MaterialPageRoute(
        // ProviderScopeを使いScopedProviderの値を上書きできる
        // ここでは、最初に表示する画像の番号を指定
        builder: (_) => ProviderScope(
          overrides: [
            photoViewInitialIndexProvider.overrideWithValue(initialIndex)
          ],
          child: PhotoViewScreen(),
        ),
      ),
    );
  }

  // ...
}

// ...