почти готовая 6 лаба на депрессивном опять

lib/components/utils/debounce.dart

@@ -0,0 +1,20 @@
+import 'dart:async';
+import 'dart:ui';
+
+class Debounce {
+  factory Debounce() => _instance;
+
+  Debounce._();
+
+  static final Debounce _instance = Debounce._();
+
+  static Timer? _timer;
+
+  static void run (
+      VoidCallback action, {
+        Duration delay = const Duration(milliseconds: 500),
+  }) {
+    _timer?.cancel();
+    _timer = Timer(delay, action);
+  }
+}

lib/data/dtos/characters_dto.dart

@@ -5,8 +5,12 @@ part 'characters_dto.g.dart';
 @JsonSerializable(createToJson: false)
 class CharactersDto {
   final List<CharacterDataDto>? data;
+  final MetaDto? meta;
 
-  const CharactersDto({this.data});
+  const CharactersDto({
+    this.data,
+    this.meta,
+  });
 
   factory CharactersDto.fromJson(Map<String, dynamic> json) => _$CharactersDtoFromJson(json);
 }
@@ -34,3 +38,23 @@ class CharacterAttributesDataDto {
   factory CharacterAttributesDataDto.fromJson(Map<String, dynamic> json) =>
       _$CharacterAttributesDataDtoFromJson(json);
 }
+
+@JsonSerializable(createToJson: false)
+class MetaDto {
+  final PaginationDto? pagination;
+
+  const MetaDto({this.pagination});
+
+  factory MetaDto.fromJson(Map<String, dynamic> json) => _$MetaDtoFromJson(json);
+}
+
+@JsonSerializable(createToJson: false)
+class PaginationDto {
+  final int? current;
+  final int? next;
+  final int? last;
+
+  const PaginationDto({this.current, this.next, this.last});
+
+  factory PaginationDto.fromJson(Map<String, dynamic> json) => _$PaginationDtoFromJson(json);
+}

lib/data/dtos/characters_dto.g.dart

@@ -11,6 +11,9 @@ CharactersDto _$CharactersDtoFromJson(Map<String, dynamic> json) =>
       data: (json['data'] as List<dynamic>?)
           ?.map((e) => CharacterDataDto.fromJson(e as Map<String, dynamic>))
           .toList(),
+      meta: json['meta'] == null
+          ? null
+          : MetaDto.fromJson(json['meta'] as Map<String, dynamic>),
     );
 
 CharacterDataDto _$CharacterDataDtoFromJson(Map<String, dynamic> json) =>
@@ -31,3 +34,16 @@ CharacterAttributesDataDto _$CharacterAttributesDataDtoFromJson(
       died: json['died'] as String?,
       image: json['image'] as String?,
     );
+
+MetaDto _$MetaDtoFromJson(Map<String, dynamic> json) => MetaDto(
+      pagination: json['pagination'] == null
+          ? null
+          : PaginationDto.fromJson(json['pagination'] as Map<String, dynamic>),
+    );
+
+PaginationDto _$PaginationDtoFromJson(Map<String, dynamic> json) =>
+    PaginationDto(
+      current: (json['current'] as num?)?.toInt(),
+      next: (json['next'] as num?)?.toInt(),
+      last: (json['last'] as num?)?.toInt(),
+    );

lib/data/mappers/characters_mapper.dart

@@ -1,9 +1,18 @@
 import 'package:mobilki_lab1/data/dtos/characters_dto.dart';
 import 'package:mobilki_lab1/domain/models/card.dart';
 
+import '../../domain/models/home.dart';
+
 const _imagePlaceholder =
     'https://upload.wikimedia.org/wikipedia/en/archive/b/b1/20210811082420%21Portrait_placeholder.png';
 
+extension CharactersDtoToModel on CharactersDto {
+  HomeData toDomain() => HomeData(
+    data: data?.map((e) => e.toDomain()).toList(),
+    nextPage: meta?.pagination?.next,
+  );
+}
+
 extension CharacterDataDtoToModel on CharacterDataDto {
   CardData toDomain() => CardData(
     attributes?.name ?? 'UNKNOWN',

lib/data/repositories/api_interface.dart

@@ -1,7 +1,8 @@
 import 'package:mobilki_lab1/domain/models/card.dart';
+import 'package:mobilki_lab1/domain/models/home.dart';
 
 typedef OnErrorCallback = void Function(String? error);
 
 abstract class ApiInterface {
-  Future<List<CardData>?> loadData({OnErrorCallback? onError});
+  Future<HomeData?> loadData({OnErrorCallback? onError});
 }

lib/data/repositories/mock_repository.dart

@@ -1,11 +1,13 @@
 import 'package:flutter/material.dart';
 import 'package:mobilki_lab1/data/repositories/api_interface.dart';
 import 'package:mobilki_lab1/domain/models/card.dart';
+import 'package:mobilki_lab1/domain/models/home.dart';
 
 class MockRepository extends ApiInterface {
   @override
-  Future<List<CardData>?> loadData({OnErrorCallback? onError}) async {
+  Future<HomeData?> loadData({OnErrorCallback? onError}) async {
-    return [
+    return HomeData(
+      data: [
         CardData(
           'Freeze',
           descriptionText: 'so cold..',
@@ -25,6 +27,7 @@ class MockRepository extends ApiInterface {
           icon: Icons.warning_amber,
           imageUrl: 'https://furmanagers.com/wp-content/uploads/2019/11/dreamstime_l_22075357.jpg',
         ),
-    ];
+      ],
+    );
   }
 }

lib/data/repositories/pokemon_repository.dart

@@ -1,43 +0,0 @@
-import 'package:dio/dio.dart';
-import 'package:mobilki_lab1/data/dtos/pokemon_dto.dart';
-import 'package:mobilki_lab1/data/mappers/pokemon_mapper.dart';
-import 'package:mobilki_lab1/data/repositories/api_interface.dart';
-import 'package:mobilki_lab1/domain/models/card.dart';
-import 'package:pretty_dio_logger/pretty_dio_logger.dart';
-
-class PokemonRepository extends ApiInterface {
-  static final Dio _dio = Dio()
-    ..interceptors.add(PrettyDioLogger(
-      requestHeader: true,
-      requestBody: true,
-    ));
-
-  static const String _baseUrl = 'https://pokeapi.co/api/v2';
-
-  @override
-  Future<List<CardData>?> loadData({String? q, OnErrorCallback? onError}) async {
-    try {
-      final String url = '$_baseUrl/pokemon';
-
-      final Response<dynamic> response = await _dio.get<Map<dynamic, dynamic>>(
-        url,
-        queryParameters: q != null ? {'name': q} : null,
-      );
-
-      final List<dynamic> results = response.data['results'] as List<dynamic>;
-      final List<CardData> data = [];
-
-      for (final result in results) {
-        final String pokemonUrl = result['url'] as String;
-        final Response<dynamic> pokemonResponse = await _dio.get<Map<dynamic, dynamic>>(pokemonUrl);
-        final PokemonDto pokemonDto = PokemonDto.fromJson(pokemonResponse.data as Map<String, dynamic>);
-        data.add(pokemonDto.toDomain());
-      }
-
-      return data;
-    } on DioException catch (e) {
-      onError?.call(e.response?.statusMessage);
-      return null;
-    }
-  }
-}

lib/data/repositories/potter_repository.dart

@@ -3,6 +3,8 @@ import 'package:mobilki_lab1/data/dtos/characters_dto.dart';
 import 'package:mobilki_lab1/data/mappers/characters_mapper.dart';
 import 'package:mobilki_lab1/data/repositories/api_interface.dart';
 import 'package:mobilki_lab1/domain/models/card.dart';
+import 'package:mobilki_lab1/domain/models/home.dart';
+import 'package:mobilki_lab1/presentation/home_page/bloc/events.dart';
 import 'package:pretty_dio_logger/pretty_dio_logger.dart';
 
 class PotterRepository extends ApiInterface {
@@ -15,20 +17,29 @@ class PotterRepository extends ApiInterface {
   static const String _baseUrl = 'https://api.potterdb.com';
 
   @override
-  Future<List<CardData>?> loadData({String? q, OnErrorCallback? onError}) async {
+  Future<HomeData?> loadData({
+    OnErrorCallback? onError,
+    String? q,
+    int page = 1,
+    int pageSize = 5,
+  }) async {
     try {
       const String url = '$_baseUrl/v1/characters';
 
       final Response<dynamic> response = await _dio.get<Map<dynamic, dynamic>>(
         url,
-        queryParameters: q != null ? {'filter[name_cont]': q} : null,
+        queryParameters: {
+          'filter[name_cont]': q,
+          'page[number]': page,
+          'page[size]': pageSize,
+        },
       );
 
       final CharactersDto dto = CharactersDto.fromJson(response.data as Map<String, dynamic>);
-      final List<CardData>? data = dto.data?.map((e) => e.toDomain()).toList();
+      final HomeData data = dto.toDomain();
       return data;
     } on DioException catch (e) {
-      onError?.call(e.response?.statusMessage);
+      onError?.call(e.error?.toString());
       return null;
     }
   }

lib/domain/models/home.dart

@@ -0,0 +1,8 @@
+import 'card.dart';
+
+class HomeData {
+  final List<CardData>? data;
+  final int? nextPage;
+
+  HomeData({this.data, this.nextPage});
+}

lib/main.dart

@@ -1,5 +1,8 @@
 import 'package:flutter/material.dart';
+import 'package:flutter_bloc/flutter_bloc.dart';
+import 'package:mobilki_lab1/presentation/home_page/bloc/bloc.dart';
 import 'package:mobilki_lab1/presentation/home_page/home_page.dart';
+import 'data/repositories/potter_repository.dart';
 
 void main() {
   runApp(const MyApp());
@@ -17,7 +20,15 @@ class MyApp extends StatelessWidget {
         colorScheme: ColorScheme.fromSeed(seedColor: Colors.deepPurple),
         useMaterial3: true,
       ),
-      home: const MyHomePage(title: 'Чубыкина Полина Павловна'),
+      home: RepositoryProvider<PotterRepository>(
+        lazy: true,
+        create: (_) => PotterRepository(),
+        child: BlocProvider<HomeBloc>(
+          lazy: false,
+          create: (context) => HomeBloc(context.read<PotterRepository>()),
+          child: const MyHomePage(title: 'Чубыкина Полина Павловна'),
+        ),
+      ),
     );
   }
 }

lib/presentation/home_page/bloc/bloc.dart

@@ -0,0 +1,39 @@
+import 'package:flutter_bloc/flutter_bloc.dart';
+import 'package:mobilki_lab1/data/repositories/potter_repository.dart';
+import 'package:mobilki_lab1/presentation/home_page/bloc/events.dart';
+import 'package:mobilki_lab1/presentation/home_page/bloc/state.dart';
+
+class HomeBloc extends Bloc<HomeEvent, HomeState> {
+  final PotterRepository repo;
+
+  HomeBloc(this.repo) : super(const HomeState()) {
+    on<HomeLoadDataEvent>(_onLoadData);
+  }
+
+  Future<void> _onLoadData(HomeLoadDataEvent event, Emitter<HomeState> emit) async {
+    if (event.nextPage == null) {
+      emit(state.copyWith(isLoading: true));
+    } else {
+      emit(state.copyWith(isPaginationLoading: true));
+    }
+
+    String? error;
+
+    final data = await repo.loadData(
+      q: event.search,
+      page: event.nextPage ?? 1,
+      onError: (e) => error = e,
+    );
+
+    if (event.nextPage != null) {
+      data?.data?.insertAll(0, state.data?.data ?? []);
+    }
+
+    emit(state.copyWith(
+      isLoading: false,
+      isPaginationLoading: false,
+      data: data,
+      error: error,
+    ));
+  }
+}

lib/presentation/home_page/bloc/events.dart

@@ -0,0 +1,10 @@
+abstract class HomeEvent {
+  const HomeEvent();
+}
+
+class HomeLoadDataEvent extends HomeEvent {
+  final String? search;
+  final int? nextPage;
+
+  const HomeLoadDataEvent({this.search, this.nextPage});
+}

lib/presentation/home_page/bloc/state.dart

@@ -0,0 +1,29 @@
+import 'package:copy_with_extension/copy_with_extension.dart';
+import 'package:equatable/equatable.dart';
+
+import '../../../domain/models/home.dart';
+
+part 'state.g.dart';
+
+@CopyWith()
+class HomeState extends Equatable {
+  final HomeData? data;
+  final bool isLoading;
+  final bool isPaginationLoading;
+  final String? error;
+
+  const HomeState({
+    this.data,
+    this.isLoading = false,
+    this.isPaginationLoading = false,
+    this.error,
+  });
+
+  @override
+  List<Object?> get props => [
+    data,
+    isLoading,
+    isPaginationLoading,
+    error,
+  ];
+}

lib/presentation/home_page/bloc/state.g.dart

@@ -0,0 +1,92 @@
+// GENERATED CODE - DO NOT MODIFY BY HAND
+
+part of 'state.dart';
+
+// **************************************************************************
+// CopyWithGenerator
+// **************************************************************************
+
+abstract class _$HomeStateCWProxy {
+  HomeState data(HomeData? data);
+
+  HomeState isLoading(bool isLoading);
+
+  HomeState isPaginationLoading(bool isPaginationLoading);
+
+  HomeState error(String? error);
+
+  /// This function **does support** nullification of nullable fields. All `null` values passed to `non-nullable` fields will be ignored. You can also use `HomeState(...).copyWith.fieldName(...)` to override fields one at a time with nullification support.
+  ///
+  /// Usage
+  /// ```dart
+  /// HomeState(...).copyWith(id: 12, name: "My name")
+  /// ````
+  HomeState call({
+    HomeData? data,
+    bool? isLoading,
+    bool? isPaginationLoading,
+    String? error,
+  });
+}
+
+/// Proxy class for `copyWith` functionality. This is a callable class and can be used as follows: `instanceOfHomeState.copyWith(...)`. Additionally contains functions for specific fields e.g. `instanceOfHomeState.copyWith.fieldName(...)`
+class _$HomeStateCWProxyImpl implements _$HomeStateCWProxy {
+  const _$HomeStateCWProxyImpl(this._value);
+
+  final HomeState _value;
+
+  @override
+  HomeState data(HomeData? data) => this(data: data);
+
+  @override
+  HomeState isLoading(bool isLoading) => this(isLoading: isLoading);
+
+  @override
+  HomeState isPaginationLoading(bool isPaginationLoading) =>
+      this(isPaginationLoading: isPaginationLoading);
+
+  @override
+  HomeState error(String? error) => this(error: error);
+
+  @override
+
+  /// This function **does support** nullification of nullable fields. All `null` values passed to `non-nullable` fields will be ignored. You can also use `HomeState(...).copyWith.fieldName(...)` to override fields one at a time with nullification support.
+  ///
+  /// Usage
+  /// ```dart
+  /// HomeState(...).copyWith(id: 12, name: "My name")
+  /// ````
+  HomeState call({
+    Object? data = const $CopyWithPlaceholder(),
+    Object? isLoading = const $CopyWithPlaceholder(),
+    Object? isPaginationLoading = const $CopyWithPlaceholder(),
+    Object? error = const $CopyWithPlaceholder(),
+  }) {
+    return HomeState(
+      data: data == const $CopyWithPlaceholder()
+          ? _value.data
+          // ignore: cast_nullable_to_non_nullable
+          : data as HomeData?,
+      isLoading: isLoading == const $CopyWithPlaceholder() || isLoading == null
+          ? _value.isLoading
+          // ignore: cast_nullable_to_non_nullable
+          : isLoading as bool,
+      isPaginationLoading:
+          isPaginationLoading == const $CopyWithPlaceholder() ||
+                  isPaginationLoading == null
+              ? _value.isPaginationLoading
+              // ignore: cast_nullable_to_non_nullable
+              : isPaginationLoading as bool,
+      error: error == const $CopyWithPlaceholder()
+          ? _value.error
+          // ignore: cast_nullable_to_non_nullable
+          : error as String?,
+    );
+  }
+}
+
+extension $HomeStateCopyWith on HomeState {
+  /// Returns a callable class that can be used as follows: `instanceOfHomeState.copyWith(...)` or like so:`instanceOfHomeState.copyWith.fieldName(...)`.
+  // ignore: library_private_types_in_public_api
+  _$HomeStateCWProxy get copyWith => _$HomeStateCWProxyImpl(this);
+}

lib/presentation/home_page/home_page.dart

@@ -1,9 +1,15 @@
 import 'package:flutter/cupertino.dart';
 import 'package:flutter/material.dart';
+import 'package:flutter_bloc/flutter_bloc.dart';
+import 'package:mobilki_lab1/components/utils/debounce.dart';
 import 'package:mobilki_lab1/data/repositories/potter_repository.dart';
 import 'package:mobilki_lab1/data/repositories/pokemon_repository.dart';
 import 'package:mobilki_lab1/domain/models/card.dart';
+import 'package:mobilki_lab1/main.dart';
 import 'package:mobilki_lab1/presentation/details_page/details_page.dart';
+import 'package:mobilki_lab1/presentation/home_page/bloc/bloc.dart';
+import 'package:mobilki_lab1/presentation/home_page/bloc/events.dart';
+import 'package:mobilki_lab1/presentation/home_page/bloc/state.dart';
 
 part 'card.dart';
 
@@ -24,25 +30,46 @@ class _MyHomePageState extends State<MyHomePage> {
 }
 
 class Body extends StatefulWidget {
-  const Body({super.key});
+  const Body();
 
   @override
-  State<Body> createState() => _BodyState();
+  State<Body> createState() => BodyState();
 }
 
-class _BodyState extends State<Body> {
+class BodyState extends State<Body> {
   final searchController = TextEditingController();
-  late Future<List<CardData>?> data;
+  final scrollController = ScrollController();
-
-  final repo = PokemonRepository();
-  //final repo = PotterRepository();
 
   @override
   void initState() {
-    data = repo.loadData();
+    WidgetsBinding.instance.addPostFrameCallback((_) {
+      context.read<HomeBloc>().add(const HomeLoadDataEvent());
+    });
+
+    scrollController.addListener(_onNextPageListener);
+
     super.initState();
   }
 
+  void _onNextPageListener() {
+    if (scrollController.offset > scrollController.position.maxScrollExtent) {
+      final bloc = context.read<HomeBloc>();
+      if (!bloc.state.isPaginationLoading) {
+        bloc.add(HomeLoadDataEvent(
+          search: searchController.text,
+          nextPage: bloc.state.data?.nextPage,
+        ));
+      }
+    }
+  }
+
+  @override
+  void dispose() {
+    searchController.dispose();
+    scrollController.dispose();
+    super.dispose();
+  }
+
   @override
   Widget build(BuildContext context) {
     return Padding(
@@ -54,40 +81,55 @@ class _BodyState extends State<Body> {
             child: CupertinoSearchTextField(
               controller: searchController,
               onChanged: (search) {
-                setState(() {
+                Debounce.run(() => context.read<HomeBloc>().add(HomeLoadDataEvent(search: search)));
-                  data = repo.loadData(q: search);
-                });
               },
             ),
           ),
-          Expanded(
+          BlocBuilder<HomeBloc, HomeState>(
-            child: Center(
+            builder: (context, state) => state.error != null
-              child: FutureBuilder<List<CardData>?>(
+                ? Text(
-                future: data,
+              state.error ?? '',
-                builder: (context, snapshot) => SingleChildScrollView(
+              style: Theme.of(context).textTheme.headlineSmall?.copyWith(color: Colors.red),
-                  child: snapshot.hasData
+            )
-                      ? Column(
+                : state.isLoading
-                    mainAxisAlignment: MainAxisAlignment.center,
+                ? const CircularProgressIndicator()
-                    children: snapshot.data?.map((data) {
+                : Expanded(
-                      return _Card.fromData(
+              child: RefreshIndicator(
+                onRefresh: _onRefresh,
+                child: ListView.builder(
+                  controller: scrollController,
+                  padding: EdgeInsets.zero,
+                  itemCount: state.data?.data?.length ?? 0,
+                  itemBuilder: (context, index) {
+                    final data = state.data?.data?[index];
+                    return data != null
+                        ? _Card.fromData(
                       data,
-                        onLike: (String title, bool isLiked) =>
+                      onLike: (title, isLiked) =>
                           _showSnackBar(context, title, isLiked),
                       onTap: () => _navToDetails(context, data),
-                      );
-                    }).toList() ??
-                        [],
                     )
-                      : const CircularProgressIndicator(),
+                        : const SizedBox.shrink();
+                  },
                 ),
               ),
             ),
           ),
+          BlocBuilder<HomeBloc, HomeState>(
+            builder: (context, state) => state.isPaginationLoading
+                ? const CircularProgressIndicator()
+                : const SizedBox.shrink(),
+          ),
         ],
       ),
     );
   }
 
+  Future<void> _onRefresh() {
+    context.read<HomeBloc>().add(HomeLoadDataEvent(search: searchController.text));
+    return Future.value(null);
+  }
+
   void _navToDetails(BuildContext context, CardData data) {
     Navigator.push(
       context,
@@ -99,7 +141,7 @@ class _BodyState extends State<Body> {
     WidgetsBinding.instance.addPostFrameCallback((_) {
       ScaffoldMessenger.of(context).showSnackBar(SnackBar(
         content: Text(
-          '${isLiked ? 'Вам понравился $title!' : 'Вам больше не нравится $title :('}',
+          '$title ${isLiked ? 'liked!' : 'disliked :('}',
           style: Theme.of(context).textTheme.bodyLarge,
         ),
         backgroundColor: Colors.orangeAccent,

pubspec.lock

@@ -38,6 +38,14 @@ packages:
       url: "https://pub.dev"
     source: hosted
     version: "2.11.0"
+  bloc:
+    dependency: transitive
+    description:
+      name: bloc
+      sha256: "106842ad6569f0b60297619e9e0b1885c2fb9bf84812935490e6c5275777804e"
+      url: "https://pub.dev"
+    source: hosted
+    version: "8.1.4"
   boolean_selector:
     dependency: transitive
     description:
@@ -158,6 +166,22 @@ packages:
       url: "https://pub.dev"
     source: hosted
     version: "3.1.1"
+  copy_with_extension:
+    dependency: transitive
+    description:
+      name: copy_with_extension
+      sha256: fbcf890b0c34aedf0894f91a11a579994b61b4e04080204656b582708b5b1125
+      url: "https://pub.dev"
+    source: hosted
+    version: "5.0.4"
+  copy_with_extension_gen:
+    dependency: "direct main"
+    description:
+      name: copy_with_extension_gen
+      sha256: "51cd11094096d40824c8da629ca7f16f3b7cea5fc44132b679617483d43346b0"
+      url: "https://pub.dev"
+    source: hosted
+    version: "5.0.4"
   crypto:
     dependency: transitive
     description:
@@ -198,6 +222,14 @@ packages:
       url: "https://pub.dev"
     source: hosted
     version: "2.0.0"
+  equatable:
+    dependency: "direct main"
+    description:
+      name: equatable
+      sha256: c2b87cb7756efdf69892005af546c56c0b5037f54d2a88269b4f347a505e3ca2
+      url: "https://pub.dev"
+    source: hosted
+    version: "2.0.5"
   fake_async:
     dependency: transitive
     description:
@@ -227,6 +259,14 @@ packages:
     description: flutter
     source: sdk
     version: "0.0.0"
+  flutter_bloc:
+    dependency: "direct main"
+    description:
+      name: flutter_bloc
+      sha256: b594505eac31a0518bdcb4b5b79573b8d9117b193cc80cc12e17d639b10aa27a
+      url: "https://pub.dev"
+    source: hosted
+    version: "8.1.6"
   flutter_lints:
     dependency: "direct dev"
     description:
@@ -392,6 +432,14 @@ packages:
       url: "https://pub.dev"
     source: hosted
     version: "2.0.0"
+  nested:
+    dependency: transitive
+    description:
+      name: nested
+      sha256: "03bac4c528c64c95c722ec99280375a6f2fc708eec17c7b3f07253b626cd2a20"
+      url: "https://pub.dev"
+    source: hosted
+    version: "1.0.0"
   package_config:
     dependency: transitive
     description:
@@ -424,6 +472,14 @@ packages:
       url: "https://pub.dev"
     source: hosted
     version: "1.4.0"
+  provider:
+    dependency: transitive
+    description:
+      name: provider
+      sha256: c8a055ee5ce3fd98d6fc872478b03823ffdb448699c6ebdbbc71d59b596fd48c
+      url: "https://pub.dev"
+    source: hosted
+    version: "6.1.2"
   pub_semver:
     dependency: transitive
     description:

pubspec.yaml

@@ -15,6 +15,11 @@ dependencies:
   dio: ^5.4.2+1
   pretty_dio_logger: ^1.3.1
 
+  equatable: ^2.0.5
+  flutter_bloc: ^8.1.5
+
+  copy_with_extension_gen: ^5.0.4
+
 dev_dependencies:
   flutter_test:
     sdk: flutter