// 抽象类 Shape
abstract class Shape {
  // 抽象方法：计算面积，子类必须实现
  double getArea();

  // 非抽象方法：打印信息
  void printInfo() {
    print("This is a shape.");
  }
}

// Circle 类继承 Shape
class Circle extends Shape {
  double radius;

  Circle(this.radius);

  @override
  double getArea() {
    return 3.14159 * radius * radius;
  }

  @override
  void printInfo() {
    super.printInfo(); // 调用父类的非抽象方法
    print("This is a circle with radius $radius.");
  }
}

// Rectangle 类继承 Shape
class Rectangle extends Shape {
  double width;
  double height;

  Rectangle(this.width, this.height);

  @override
  double getArea() {
    return width * height;
  }
}

void main() {
  // Shape shape = Shape(); // 错误：抽象类不能直接实例化

  var circle = Circle(5.0);
  print("Circle Area: ${circle.getArea()}"); // 输出: Circle Area: 78.53975
  circle.printInfo(); // 输出: This is a shape.
                      //       This is a circle with radius 5.0.

  var rectangle = Rectangle(4.0, 6.0);
  print("Rectangle Area: ${rectangle.getArea()}"); // 输出: Rectangle Area: 24.0
}

// 定义一个行为接口 (隐式接口)
class Flyable {
  void fly() {
    print("I can fly!");
  }
}

class Swimmable {
  void swim() {
    print("I can swim!");
  }
}

// Bird 类实现 Flyable 接口
class Bird implements Flyable {
  String name;

  Bird(this.name);

  @override
  void fly() {
    print("$name is flying high.");
  }
}

// Duck 类实现 Flyable 和 Swimmable 接口
class Duck implements Flyable, Swimmable {
  String name;

  Duck(this.name);

  @override
  void fly() {
    print("$name is flying low.");
  }

  @override
  void swim() {
    print("$name is swimming in the pond.");
  }
}

void main() {
  var bird = Bird("Eagle");
  bird.fly(); // 输出: Eagle is flying high.

  var duck = Duck("Donald");
  duck.fly();  // 输出: Donald is flying low.
  duck.swim(); // 输出: Donald is swimming in the pond.
}

import 'package:flutter/material.dart';

// 抽象类：定义主题的通用接口
abstract class AppTheme {
  String get themeName;
  Color get primaryColor;
  Color get accentColor;
  Color get textColor;
  Color get backgroundColor;

  // 抽象方法，子类实现具体的主题样式
  ThemeData getThemeData();
}

// 亮色主题实现
class LightTheme implements AppTheme {
  @override
  String get themeName => '亮色主题';

  @override
  Color get primaryColor => Colors.blue;

  @override
  Color get accentColor => Colors.lightBlueAccent;

  @override
  Color get textColor => Colors.black87;

  @override
  Color get backgroundColor => Colors.white;

  @override
  ThemeData getThemeData() {
    return ThemeData(
      brightness: Brightness.light,
      primaryColor: primaryColor,
      colorScheme: ColorScheme.light(
        primary: primaryColor,
        secondary: accentColor,
      ),
      scaffoldBackgroundColor: backgroundColor,
      textTheme: TextTheme(
        bodyMedium: TextStyle(color: textColor),
      ),
      appBarTheme: AppBarTheme(
        backgroundColor: primaryColor,
        foregroundColor: Colors.white,
      ),
    );
  }
}

// 暗色主题实现
class DarkTheme implements AppTheme {
  @override
  String get themeName => '暗色主题';

  @override
  Color get primaryColor => Colors.deepPurple;

  @override
  Color get accentColor => Colors.purpleAccent;

  @override
  Color get textColor => Colors.white70;

  @override
  Color get backgroundColor => Colors.grey[900]!;

  @override
  ThemeData getThemeData() {
    return ThemeData(
      brightness: Brightness.dark,
      primaryColor: primaryColor,
      colorScheme: ColorScheme.dark(
        primary: primaryColor,
        secondary: accentColor,
      ),
      scaffoldBackgroundColor: backgroundColor,
      textTheme: TextTheme(
        bodyMedium: TextStyle(color: textColor),
      ),
      appBarTheme: AppBarTheme(
        backgroundColor: primaryColor,
        foregroundColor: Colors.white,
      ),
    );
  }
}

class ThemeSwitcherApp extends StatefulWidget {
  const ThemeSwitcherApp({super.key});

  @override
  State<ThemeSwitcherApp> createState() => _ThemeSwitcherAppState();
}

class _ThemeSwitcherAppState extends State<ThemeSwitcherApp> {
  AppTheme _currentTheme = LightTheme(); // 初始主题为亮色主题

  void _toggleTheme() {
    setState(() {
      // 根据当前主题切换到另一个主题
      if (_currentTheme is LightTheme) {
        _currentTheme = DarkTheme();
      } else {
        _currentTheme = LightTheme();
      }
    });
  }

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      theme: _currentTheme.getThemeData(), // 应用当前主题
      home: Scaffold(
        appBar: AppBar(
          title: Text(_currentTheme.themeName), // 显示当前主题名称
        ),
        body: Center(
          child: Column(
            mainAxisAlignment: MainAxisAlignment.center,
            children: <Widget>[
              Text(
                'Hello, Flutter!',
                style: TextStyle(
                  fontSize: 30,
                  color: _currentTheme.textColor, // 使用当前主题的文本颜色
                ),
              ),
              const SizedBox(height: 20),
              ElevatedButton(
                onPressed: _toggleTheme,
                child: const Text('切换主题'),
              ),
            ],
          ),
        ),
      ),
    );
  }
}

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