[Flutter]实现i18n，运行时切换简繁英 [Flutter]实现i18n，运行时切换简

一、导包
引入“flutter_localizations包”，并且“flutter packages get”：

dependencies:...flutter_localizations:sdk: flutter

二、添加协议以及支持语言

import 'package:flutter_localizations/flutter_localizations.dart'; ... return MaterialApp( ... localizationsDelegates: [ GlobalMaterialLocalizations.delegate, GlobalWidgetsLocalizations.delegate, ], supportedLocales: [ const Locale('zh', 'CN'), const Locale('zh', 'HK'), const Locale('zh', 'TW'), const Locale('en', 'US'), ], ); //MaterialApp

三、编写Localizations类
Localizations汇总所有翻译文本

import 'package:flutter/material.dart'; classMyLocalizations { final Locale locale; MyLocalizations(this.locale); static Map> _localizedValuesMap = { 'en_US': { 'test_text': 'Test Text', }, 'zh_CN': { 'test_text': '测试文字', }, 'zh_HK': { 'test_text': '測試文字', }, 'zh_TW': { 'test_text': '測試文字', } }; get testText{ ///注意用 locale.toString()而非locale return _localizedValuesMap[locale.toString()]['test_text']; }///MyLocalizations的实例是在 Localizations中通过 MyLocalizationsDelegate实例化, ///应用中要使用 MyLocalizations的实例需要通过 Localizations这个 Widget来获取。 static MyLocalizations of(BuildContext context){ return Localizations.of(context, MyLocalizations); } }

四、实现LocalizationsDelegate协议，用于初始化Localizations类

import 'package:flutter/foundation.dart'; import 'package:flutter/material.dart'; import 'package:gd_i18n_project/MyLocalizations.dart'; class MyLocalizationsDelegate extends LocalizationsDelegate{ const MyLocalizationsDelegate(); static MyLocalizationsDelegate delegate = const MyLocalizationsDelegate(); @override bool isSupported(Locale locale) { return ['en','zh'].contains(locale.languageCode); }@override Future load(Locale locale) { ///这里初始化 Localizations类 return SynchronousFuture(new MyLocalizations(locale)); }@override bool shouldReload(LocalizationsDelegate old) { return false; } }

添加到"localizationsDelegates":

return MaterialApp( ... localizationsDelegates: [ GlobalMaterialLocalizations.delegate, GlobalWidgetsLocalizations.delegate, ///自定义 LocalizationsDelegate协议； MyLocalizationsDelegate(), ], ... ); ///MaterialApp

五、替换应用的Title

class MyApp extends StatelessWidget { @override Widget build(BuildContext context) { return new MaterialApp( onGenerateTitle: (context){ //默认的 build()的 context对象无法获得 MyLocalizations对象， //所以这里引用 onGenerateTitle的 context对象。 return MyLocalizations.of(context).testText; }, ...

六、替换MyHomePage的Title

Widget build(BuildContext context) { return MaterialApp( ... //修改MyHomePage()的构造函数，去掉title home: MyHomePage(), ...

class _MyHomePageState extends State { @override Widget build(BuildContext context) { return Scaffold( appBar: AppBar( //同第五步，默认的 build()的 context对象无法获得 MyLocalizations对象。 title: Text(MyLocalizations.of(context).testText), ), ...

到这一步应用能跟随系统更改语言。
七、运行时更改语言

import 'package:flutter/material.dart'; ///用于操作子widget运行时更改语言 class MyI18nWidget extends StatefulWidget { final child; MyI18nWidget({this.child, Key key}):super(key:key); @override State createState() => MyI18nWidgetState(); }class MyI18nWidgetState extends State { var _locale; @override void didChangeDependencies() { super.didChangeDependencies(); //获取当前设备语言 _locale = Localizations.localeOf(context); }///动态切换子widget的语言 void changeLanguage(Locale locale){ setState(() { _locale=locale; }); }@override Widget build(BuildContext context) { return Localizations.override( context: context, locale: _locale, child: widget.child, ); } }

void main() => runApp(MyApp()); ///用于外部获取MyI18nWidgetState来调用其changeLanguage(); GlobalKey myI18nWidgetStateKey=GlobalKey(); class MyApp extends StatelessWidget { ... }

return MaterialApp( ... //MyI18nWidget作为MyHomePage的父widget home: MyI18nWidget( key: myI18nWidgetStateKey, child: MyHomePage( ), ), ... )//MaterialApp//指定地方调用，动态更改语言 myI18nWidgetStateKey.currentState.changeLanguage(Locale('en','US'));

参考