多主题

主题（UI风格、样式、皮肤）

  主题风格可通过 theme 来定义，从而实现整个 App 风格的统一

  一旦设置了主题，那么应用程序中的某些 Widget，就会直接使用主题的样式

组件

  ThemeData

    - Brightness (Brightness.light | Brightness.dark)

    - primaryColor | accentColor

    - buttonTheme | cardTheme | iconTheme | textTheme

// main.dart

import 'package:flutter/material.dart';
import 'package:flutter_localizations/flutter_localizations.dart';
import '11_theme/CustomLocalizations.dart';
import '11_theme/theme_02_style.dart';

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

class MyApp extends StatelessWidget {
  const MyApp({Key? key}) : super(key: key);

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: "Flutter Demo",
      home: const Home(),
      debugShowCheckedModeBanner: false,
      // 设置主题风格
      theme: ThemeData(
        primaryColor: Colors.red,
        // accentColor: Colors.yellow,
        textTheme: const TextTheme(
          subtitle1: TextStyle(
            fontSize: 30,
            color: Colors.purple,
          ),
        ),
        iconTheme: const IconThemeData(
          color: Colors.amber,
          size: 40,
        ),
        cardTheme: CardTheme(
          color: Colors.blueGrey[200],
          shape: Border.all( 10, color: Colors.red),
          elevation: 20,
        ),
      ),
      // 国际化
      localizationsDelegates: [
        // 本地化代理
        CustomLocalizations.delegate,
        GlobalMaterialLocalizations.delegate, // Material 国际化
        GlobalCupertinoLocalizations.delegate, // Cupertino 国际化
        GlobalWidgetsLocalizations.delegate, // 组件国际化
      ],
      supportedLocales: const [
        Locale('en', 'US'), // 美国英语
        Locale('zh', 'CN'), // 简体中文
      ],
      // 检测当前语言
      localeResolutionCallback: (locale, supportedLocales) {
        print('device locale: $locale'); // device locale: zh_Hans_CN
        print('supportedLocales: $supportedLocales'); // [en_US, zh_CN]
        for (var supportedLocale in supportedLocales) {
          print('supportedLocale: $supportedLocale');
          // supportedLocale: en_US
          // supportedLocale: zh_CN
          if (supportedLocale.languageCode == locale?.languageCode &&
              supportedLocale.countryCode == locale?.countryCode) {
            return supportedLocale;
          }
        }
        return supportedLocales.first;
      },
    );
  }
}

  Theme（声明局部主题）

    Theme.of(context) 获取上下文中的主题信息

// theme_02_style.dart

import 'package:flutter/material.dart';

class Home extends StatelessWidget {
  const Home({Key? key}) : super(key: key);

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: const Text('Theme'),
        backgroundColor: Theme.of(context).primaryColor,
      ),
      body: const ThemeDemo(),
    );
  }
}

class ThemeDemo extends StatelessWidget {
  const ThemeDemo({Key? key}) : super(key: key);

  @override
  Widget build(BuildContext context) {
    return Container(
      padding: const EdgeInsets.all(10.0),
      child: Column(
        children: [
          Text(
            'Theme Example',
            style: Theme.of(context).textTheme.subtitle1,
          ),
          ElevatedButton(
            onPressed: () {},
            child: const Text('按钮'),
          ),
          const Icon(Icons.person),
          const Icon(Icons.favorite),
          Card(
            margin: const EdgeInsets.all(10.0),
            child: Column(
              children: const [
                ListTile(
                  leading: Icon(Icons.alarm, size: 50),
                  title: Text(
                    '花果山',
                    style: TextStyle(fontSize: 30),
                  ),
                  subtitle: Text(
                    '水帘洞',
                    style: TextStyle(fontSize: 20),
                  ),
                )
              ],
            ),
          ),
        ],
      ),
    );
  }
}

多主题 - 适配终端

  声明不同的主题 CustomTheme

// main.dart

import 'package:flutter/material.dart';
import 'package:flutter_localizations/flutter_localizations.dart';
import '11_theme/CustomLocalizations.dart';
import '11_theme/theme_02_style.dart';

class MyApp extends StatelessWidget {
  const MyApp({Key? key}) : super(key: key);

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: "Flutter Demo",
      home: const Home(),
      debugShowCheckedModeBanner: false,
      // 适配终端主题风格
      theme: ThemeData.light(),
      darkTheme: ThemeData.dark(),
      // 国际化
      localizationsDelegates: [
        // 本地化代理
        CustomLocalizations.delegate,
        GlobalMaterialLocalizations.delegate, // Material 国际化
        GlobalCupertinoLocalizations.delegate, // Cupertino 国际化
        GlobalWidgetsLocalizations.delegate, // 组件国际化
      ],
      supportedLocales: const [
        Locale('en', 'US'), // 美国英语
        Locale('zh', 'CN'), // 简体中文
      ],
      // 检测当前语言
      localeResolutionCallback: (locale, supportedLocales) {
        print('device locale: $locale'); // device locale: zh_Hans_CN
        print('supportedLocales: $supportedLocales'); // [en_US, zh_CN]
        for (var supportedLocale in supportedLocales) {
          print('supportedLocale: $supportedLocale');
          // supportedLocale: en_US
          // supportedLocale: zh_CN
          if (supportedLocale.languageCode == locale?.languageCode &&
              supportedLocale.countryCode == locale?.countryCode) {
            return supportedLocale;
          }
        }
        return supportedLocales.first;
      },
    );
  }
}

  使用主题

  （1）、import 'CustomTheme.dart';

  （2）、theme: CustomTheme.lightTheme;

  （3）、darkTheme: CustomTheme.darkTheme;

  （4）、theme: ThemeData.light();

  （5）、darkTheme: ThemeData.dark();

// CustomTheme.dart

import 'package:flutter/material.dart';

class CustomTheme {
  // 公共样式
  static const double cardBorderWidth = 10;
  // 高亮主题
  static final ThemeData lightTheme = ThemeData(
    primaryColor: Colors.red,
    cardTheme: CardTheme(
      color: Colors.red[100],
      shape: Border.all( cardBorderWidth, color: Colors.red),
      elevation: 20,
    ),
  );
  // 暗黑主题
  static final ThemeData darkTheme = ThemeData(
    primaryColor: Colors.grey,
    cardTheme: CardTheme(
      color: Colors.grey[100],
      shape: Border.all( cardBorderWidth, color: Colors.black45),
      elevation: 20,
    ),
  );
}

// main.dart

import 'package:flutter/material.dart';
import 'package:flutter_localizations/flutter_localizations.dart';
import '11_theme/CustomLocalizations.dart';
import '11_theme/CustomTheme.dart';
import '11_theme/theme_02_style.dart';

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

class MyApp extends StatelessWidget {
  const MyApp({Key? key}) : super(key: key);

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: "Flutter Demo",
      home: const Home(),
      debugShowCheckedModeBanner: false,
      // 自定主题风格
      theme: CustomTheme.lightTheme,
      darkTheme: CustomTheme.darkTheme,
      // 国际化
      localizationsDelegates: [
        // 本地化代理
        CustomLocalizations.delegate,
        GlobalMaterialLocalizations.delegate, // Material 国际化
        GlobalCupertinoLocalizations.delegate, // Cupertino 国际化
        GlobalWidgetsLocalizations.delegate, // 组件国际化
      ],
      supportedLocales: const [
        Locale('en', 'US'), // 美国英语
        Locale('zh', 'CN'), // 简体中文
      ],
      // 检测当前语言
      localeResolutionCallback: (locale, supportedLocales) {
        print('device locale: $locale'); // device locale: zh_Hans_CN
        print('supportedLocales: $supportedLocales'); // [en_US, zh_CN]
        for (var supportedLocale in supportedLocales) {
          print('supportedLocale: $supportedLocale');
          // supportedLocale: en_US
          // supportedLocale: zh_CN
          if (supportedLocale.languageCode == locale?.languageCode &&
              supportedLocale.countryCode == locale?.countryCode) {
            return supportedLocale;
          }
        }
        return supportedLocales.first;
      },
    );
  }
}

  查看效果，在模拟器中切换主题，Flutter 应用中查看效果