为什么 Flutter 导入提供程序包不起作用？

Question

So following this tutorial for a simple login UI in Flutter

https://medium.com/better-programming/simple-firebase-login-flow-in-flutter-6f44c2b5c58a

Apparently this package in flutter isn't being imported correctly. The particular lines that are not working are these 3 lines of code

import 'package:provider/provider.dart';
ChangeNotifierProvider<AuthService>( //TODO: authservices and provider pages
future: Provider.of<AuthService>(context).getUser(),

I have been searching a bunch and tried reading the docs and couldn't get any easy answers, but anyway thank you to anyone who gets me the answer to this

import 'package:flutter/material.dart';
    import 'package:provider/provider.dart';
    import 'home_page.dart';
    import 'auth.dart';
    import 'login_page.dart';

void main() => runApp(
  ChangeNotifierProvider<AuthService>( //TODO: authservices and provider pages
    child: MyApp(),
    builder: (BuildContext context) {
      return AuthService();
    },
  ),
);

class MyApp extends StatelessWidget {
  // This widget is the root of your application.
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      theme: ThemeData(primarySwatch: Colors.blue),
      home: FutureBuilder(
        future: Provider.of<AuthService>(context).getUser(),
        builder: (context, AsyncSnapshot snapshot) {
          if (snapshot.connectionState == ConnectionState.done) {
            return snapshot.hasData ? HomePage() : LoginPage();
          } else {
            return Container(color: Colors.white);
          }
        },
      ),
    );
  }
}

the pubspec.yaml file for anyone looking

name: login_flutter_app
description: A new Flutter application.

# The following defines the version and build number for your application.
# A version number is three numbers separated by dots, like 1.2.43
# followed by an optional build number separated by a +.
# Both the version and the builder number may be overridden in flutter
# build by specifying --build-name and --build-number, respectively.
# In Android, build-name is used as versionName while build-number used as versionCode.
# Read more about Android versioning at https://developer.android.com/studio/publish/versioning
# In iOS, build-name is used as CFBundleShortVersionString while build-number used as CFBundleVersion.
# Read more about iOS versioning at
# https://developer.apple.com/library/archive/documentation/General/Reference/InfoPlistKeyReference/Articles/CoreFoundationKeys.html
version: 1.0.0+1

environment:
  sdk: ">=2.1.0 <3.0.0"

dependencies:
  flutter:
    sdk: flutter

  # The following adds the Cupertino Icons font to your application.
  # Use with the CupertinoIcons class for iOS style icons.
  cupertino_icons: ^0.1.2

dev_dependencies:
  flutter_test:
    sdk: flutter


# For information on the generic Dart part of this file, see the
# following page: https://dart.dev/tools/pub/pubspec

# The following section is specific to Flutter.
flutter:

  # The following line ensures that the Material Icons font is
  # included with your application, so that you can use the icons in
  # the material Icons class.
  uses-material-design: true

  # To add assets to your application, add an assets section, like this:
  # assets:
  #  - images/a_dot_burr.jpeg
  #  - images/a_dot_ham.jpeg

  # An image asset can refer to one or more resolution-specific "variants", see
  # https://flutter.dev/assets-and-images/#resolution-aware.

  # For details regarding adding assets from package dependencies, see
  # https://flutter.dev/assets-and-images/#from-packages

  # To add custom fonts to your application, add a fonts section here,
  # in this "flutter" section. Each entry in this list should have a
  # "family" key with the font family name, and a "fonts" key with a
  # list giving the asset and other descriptors for the font. For
  # example:
  # fonts:
  #   - family: Schyler
  #     fonts:
  #       - asset: fonts/Schyler-Regular.ttf
  #       - asset: fonts/Schyler-Italic.ttf
  #         style: italic
  #   - family: Trajan Pro
  #     fonts:
  #       - asset: fonts/TrajanPro.ttf
  #       - asset: fonts/TrajanPro_Bold.ttf
  #         weight: 700
  #
  # For details regarding fonts from package dependencies,
  # see https://flutter.dev/custom-fonts/#from-packages

Answer 1

Had to put these into the project

cupertino_icons: ^0.1.2 flutter_blue: ^0.6.3+1 provider: ^4.0.4

Answer 2

Just add dependency provider: ^4.1.1 in pubspec.yaml file. it looks like bellow

dependencies:
  flutter:
   sdk: flutter
  provider: ^4.1.1