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:photoapp/photo.dart';
import 'package:photoapp/photo_repository.dart';
import 'package:photoapp/photo_view_screen.dart';
import 'package:photoapp/sign_in_screen.dart';

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

class _PhotoListScreenState extends State<PhotoListScreen> {

  // ...

  @override
  Widget build(BuildContext context) {
    final User user = FirebaseAuth.instance.currentUser!;

    return Scaffold(
      // ...
      body: StreamBuilder<List<Photo>>(
        // リポジトリ経由でデータを取得する
        stream: PhotoRepository(user).getPhotoList(),
        builder: (context, snapshot) {
          if (snapshot.hasData == false) {
            return Center(
              child: CircularProgressIndicator(),
            );
          }

          // URL一覧ではなくモデル一覧が取得できる
          final List<Photo> photoList = snapshot.data!;
          return PageView(
            controller: _controller,
            onPageChanged: (int index) => _onPageChanged(index),
            children: [
              //「全ての画像」を表示する部分
              PhotoGridView(
                // 処理を行う際はモデルを受け渡す
                photoList: photoList,
                onTap: (photo) => _onTapPhoto(photo, photoList),
              ),
              //「お気に入り登録した画像」を表示する部分
              PhotoGridView(
                photoList: photoList,
                onTap: (photo) => _onTapPhoto(photo, photoList),
              ),
            ],
          );
        },
      ),
      // ...
    );
  }

  // ...

  void _onTapPhoto(Photo photo, List<Photo> photoList) {
    Navigator.of(context).push(
      MaterialPageRoute(
        // 処理を行う際はモデルを受け渡す
        builder: (_) => PhotoViewScreen(
          photo: photo,
          photoList: photoList,
        ),
      ),
    );
  }
  
  Future<void> _onAddPhoto() async {
    final FilePickerResult? result = await FilePicker.platform.pickFiles(
      type: FileType.image,
    ); 

    if (file != null) {
      // リポジトリ経由でデータを保存する
      final User user = FirebaseAuth.instance.currentUser!;
      final PhotoRepository repository = PhotoRepository(user);
      final File file = File(result.files.single.path!);
      await repository.addPhoto(file);
    }
  }
}

class PhotoGridView extends StatelessWidget {
  const PhotoGridView({
    Key? key,
    required this.photoList,
    required this.onTap,
  }) : super(key: key);

  final List<Photo> photoList;
  final Function(Photo photo) onTap;

  @override
  Widget build(BuildContext context) {
    return GridView.count(
      // ...
      children: photoList.map((Photo photo) {
        return Stack(
          children: [
            SizedBox(
              width: double.infinity,
              height: double.infinity,
              child: InkWell(
                onTap: () => onTap(photo),
                child: Image.network(
                  photo.imageURL,
                  fit: BoxFit.cover,
                ),
              ),
            ),
            // ...
          ],
        );
      }).toList(),
    );
  }
}