Flutter多语言及计算功能插件lingua_calculator的使用

当然，下面是一个关于如何在Flutter项目中使用lingua_calculator插件来实现多语言支持和基本计算功能的代码示例。请注意，lingua_calculator插件实际上是一个假设的插件名称，因为在实际Flutter生态系统中并没有直接名为lingua_calculator的插件，它可能结合了多语言（如flutter_localizations和intl）与计算功能（如自定义计算逻辑）。因此，以下示例将展示如何使用Flutter的多语言支持和实现基本的计算功能。

1. 添加依赖

首先，在你的pubspec.yaml文件中添加国际化支持所需的依赖：

dependencies:
  flutter:
    sdk: flutter
  flutter_localizations:
    sdk: flutter
  intl: ^0.17.0

2. 创建语言文件

在你的项目根目录下创建一个lib/l10n文件夹，并在其中创建两个文件：messages_en.dart和messages_zh.dart（或其他你需要的语言）。

messages_en.dart

import 'package:intl/intl.dart';

final Map<String, String> en = {
  "app_title": "Calculator",
  "add": "Add",
  "subtract": "Subtract",
  "multiply": "Multiply",
  "divide": "Divide",
  "result": "Result",
};

messages_zh.dart

import 'package:intl/intl.dart';

final Map<String, String> zh = {
  "app_title": "计算器",
  "add": "加",
  "subtract": "减",
  "multiply": "乘",
  "divide": "除",
  "result": "结果",
};

3. 本地化委托

创建一个localizations.dart文件来管理本地化委托：

import 'package:flutter/material.dart';
import 'package:intl/intl.dart';
import 'messages_en.dart';
import 'messages_zh.dart';

class AppLocalizations {
  final Locale locale;
  Map<String, String> _localizedValues;

  AppLocalizations(this.locale) {
    _localizedValues = {
      ...en, // Default to English
      ...zh, // Add Chinese translations
      // ...other languages
    };

    if (locale.languageCode == 'zh') {
      _localizedValues = zh;
    }
  }

  String get appTitle => _localizedValues['app_title'] ?? 'Calculator';
  String get addButton => _localizedValues['add'] ?? 'Add';
  String get subtractButton => _localizedValues['subtract'] ?? 'Subtract';
  String get multiplyButton => _localizedValues['multiply'] ?? 'Multiply';
  String get divideButton => _localizedValues['divide'] ?? 'Divide';
  String get resultLabel => _localizedValues['result'] ?? 'Result';
}

class AppLocalizationsDelegate extends LocalizationsDelegate<AppLocalizations> {
  const AppLocalizationsDelegate();

  @override
  bool isSupported(Locale locale) {
    return ['en', 'zh'].contains(locale.languageCode);
  }

  @override
  Future<AppLocalizations> load(Locale locale) async {
    return AppLocalizations(locale);
  }

  @override
  bool shouldReload(AppLocalizationsDelegate oldDelegate) {
    return false;
  }
}

4. 使用MaterialApp进行本地化

在你的主应用程序文件中（通常是main.dart），使用MaterialApp并配置本地化支持：

import 'package:flutter/material.dart';
import 'package:flutter_localizations/flutter_localizations.dart';
import 'localizations.dart';
import 'calculator_page.dart'; // 假设你有一个计算器页面

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

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Calculator',
      theme: ThemeData(
        primarySwatch: Colors.blue,
      ),
      localizationsDelegates: [
        AppLocalizationsDelegate(),
        GlobalMaterialLocalizations.delegate,
        GlobalWidgetsLocalizations.delegate,
        GlobalCupertinoLocalizations.delegate,
      ],
      supportedLocales: [
        Locale('en', ''),
        Locale('zh', ''),
        // Add more locales as needed
      ],
      home: CalculatorPage(),
    );
  }
}

5. 实现计算器页面

创建一个calculator_page.dart文件，并在其中实现基本的计算功能：

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

class CalculatorPage extends StatefulWidget {
  @override
  _CalculatorPageState createState() => _CalculatorPageState();
}

class _CalculatorPageState extends State<CalculatorPage> {
  final TextEditingController _controller = TextEditingController();
  double _firstNum = 0.0;
  double _secondNum = 0.0;
  String _operation = '';

  void _performOperation(String operation) {
    setState(() {
      if (_operation.isEmpty) {
        _firstNum = double.parse(_controller.text);
        _operation = operation;
        _controller.clear();
      } else if (_operation == operation) {
        _secondNum = double.parse(_controller.text) + _firstNum;
        _controller.text = _secondNum.toString();
        _operation = '';
        _firstNum = 0.0;
      } else {
        double result;
        switch (_operation) {
          case '+':
            result = _firstNum + double.parse(_controller.text);
            break;
          case '-':
            result = _firstNum - double.parse(_controller.text);
            break;
          case '*':
            result = _firstNum * double.parse(_controller.text);
            break;
          case '/':
            result = _firstNum / double.parse(_controller.text);
            break;
        }
        _controller.text = result.toString();
        _firstNum = result;
        _operation = operation;
      }
    });
  }

  @override
  Widget build(BuildContext context) {
    final localizations = AppLocalizations.of(context);
    return Scaffold(
      appBar: AppBar(
        title: Text(localizations.appTitle),
      ),
      body: Padding(
        padding: const EdgeInsets.all(16.0),
        child: Column(
          crossAxisAlignment: CrossAxisAlignment.start,
          children: [
            TextField(
              controller: _controller,
              keyboardType: TextInputType.numberWithOptions(decimal: true),
              decoration: InputDecoration(
                labelText: localizations.resultLabel,
              ),
            ),
            SizedBox(height: 16),
            Row(
              mainAxisAlignment: MainAxisAlignment.spaceAround,
              children: [
                ElevatedButton(
                  onPressed: () => _performOperation('+'),
                  child: Text(localizations.addButton),
                ),
                ElevatedButton(
                  onPressed: () => _performOperation('-'),
                  child: Text(localizations.subtractButton),
                ),
              ],
            ),
            Row(
              mainAxisAlignment: MainAxisAlignment.spaceAround,
              children: [
                ElevatedButton(
                  onPressed: () => _performOperation('*'),
                  child: Text(localizations.multiplyButton),
                ),
                ElevatedButton(
                  onPressed: () => _performOperation('/'),
                  child: Text(localizations.divideButton),
                ),
              ],
            ),
          ],
        ),
      ),
    );
  }
}

在这个示例中，我们展示了如何设置Flutter应用程序以支持多语言，并实现了一个基本的计算器功能。你可以根据实际需求进一步扩展和修改这个示例。