Flutter基础功能插件app_fundamentals的使用

在Flutter开发中，app_fundamentals 并不是一个官方的或广泛认可的包名。然而，从帖子内容来看，它可能指的是一系列用于实现Flutter应用基础功能的插件集合。为了展示如何使用这些基础功能插件，我将列举几个常见的Flutter插件及其基本用法，这些插件通常用于实现如网络请求、状态管理、本地存储等基础功能。

1. 网络请求：http 包

http 包是Flutter中用于发送HTTP请求的一个常用库。以下是一个简单的GET请求示例：

import 'package:flutter/material.dart';
import 'package:http/http.dart' as http;

void main() {
  runApp(MyApp());
}

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      home: Scaffold(
        appBar: AppBar(
          title: Text('Flutter Network Request'),
        ),
        body: Center(
          child: FutureBuilder<String>(
            future: fetchData(),
            builder: (context, snapshot) {
              if (snapshot.connectionState == ConnectionState.done) {
                if (snapshot.hasError) {
                  return Text('Error: ${snapshot.error}');
                } else {
                  return Text('Data: ${snapshot.data}');
                }
              } else {
                return CircularProgressIndicator();
              }
            },
          ),
        ),
      ),
    );
  }

  Future<String> fetchData() async {
    final response = await http.get(Uri.parse('https://jsonplaceholder.typicode.com/todos/1'));
    if (response.statusCode == 200) {
      return response.body;
    } else {
      throw Exception('Failed to load data');
    }
  }
}

2. 状态管理：provider 包

provider 包是Flutter中用于状态管理的一个流行库。以下是一个简单的示例，展示如何使用provider来管理应用状态：

import 'package:flutter/material.dart';
import 'package:provider/provider.dart';

void main() {
  runApp(
    MultiProvider(
      providers: [
        ChangeNotifierProvider(create: (_) => Counter()),
      ],
      child: MyApp(),
    ),
  );
}

class Counter with ChangeNotifier {
  int _count = 0;

  int get count => _count;

  void increment() {
    _count++;
    notifyListeners();
  }
}

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      home: Scaffold(
        appBar: AppBar(
          title: Text('Flutter Provider Example'),
        ),
        body: Center(
          child: Column(
            mainAxisAlignment: MainAxisAlignment.center,
            children: <Widget>[
              Text(
                'You have pushed the button this many times:',
              ),
              Consumer<Counter>(
                builder: (context, counter, child) => Text(
                  '${counter.count}',
                  style: Theme.of(context).textTheme.headline4,
                ),
              ),
            ],
          ),
        ),
        floatingActionButton: FloatingActionButton(
          onPressed: () {
            final counter = Provider.of<Counter>(context, listen: false);
            counter.increment();
          },
          tooltip: 'Increment',
          child: Icon(Icons.add),
        ),
      ),
    );
  }
}

3. 本地存储：shared_preferences 包

shared_preferences 包是Flutter中用于本地存储的一个常用库。以下是一个简单的示例，展示如何使用shared_preferences来存储和读取数据：

import 'package:flutter/material.dart';
import 'package:shared_preferences/shared_preferences.dart';

void main() {
  runApp(MyApp());
}

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      home: Scaffold(
        appBar: AppBar(
          title: Text('Flutter SharedPreferences Example'),
        ),
        body: SharedPreferencesDemo(),
      ),
    );
  }
}

class SharedPreferencesDemo extends StatefulWidget {
  @override
  _SharedPreferencesDemoState createState() => _SharedPreferencesDemoState();
}

class _SharedPreferencesDemoState extends State<SharedPreferencesDemo> {
  String _counterValue = '0';

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

  Future<void> _incrementCounter() async {
    SharedPreferences prefs = await SharedPreferences.getInstance();
    int counter = (prefs.getInt('counter') ?? 0) + 1;
    await prefs.setInt('counter', counter);
    setState(() {
      _counterValue = counter.toString();
    });
  }

  Future<void> _readCounter() async {
    SharedPreferences prefs = await SharedPreferences.getInstance();
    int counter = prefs.getInt('counter') ?? 0;
    setState(() {
      _counterValue = counter.toString();
    });
  }

  @override
  Widget build(BuildContext context) {
    return Center(
      child: Column(
        mainAxisAlignment: MainAxisAlignment.center,
        children: <Widget>[
          Text(
            'You have pushed the button this many times:',
          ),
          Text(
            _counterValue,
            style: Theme.of(context).textTheme.headline4,
          ),
        ],
      ),
      floatingActionButton: FloatingActionButton(
        onPressed: _incrementCounter,
        tooltip: 'Increment',
        child: Icon(Icons.add),
      ),
    );
  }
}

以上代码展示了如何使用http包进行网络请求，provider包进行状态管理，以及shared_preferences包进行本地存储。这些插件是实现Flutter应用基础功能的关键组件。