main.dart

// https://gist.github.com/NearHuscarl/29b150557e866b7910e50a84c11bb18e
// https://dartpad.dev/29b150557e866b7910e50a84c11bb18e?null_safety=true

import 'package:flutter/material.dart';

void main() => runApp(MyApp());

void main1() {
  const a = <String>[];

  a.add('1');
}

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      debugShowCheckedModeBanner: false,
      theme: ThemeData(
        primarySwatch: Colors.blue,
      ),
      home: Scaffold(
        body: Center(
          child: Column(
            mainAxisAlignment: MainAxisAlignment.center,
            children: <Widget>[
              ElevatedButton(
                onPressed: () {},
                child: Text('Button 1'),
                style: ButtonStyle(
                  backgroundColor: MaterialStateProperty.all(Colors.purple),
                ),
              ),
              SizedBox(height: 10),
              ElevatedButton(
                onPressed: () {},
                child: Text('Button 2'),
                style: ButtonStyle(
                  backgroundColor: MaterialStateProperty.resolveAs(
                      Colors.green, {MaterialState.hovered}),
                ),
              ),
              SizedBox(height: 10),
              ElevatedButton(
                onPressed: () {},
                child: Text('Button 3'),
                style: ButtonStyle(
                  backgroundColor: MaterialStateProperty.resolveWith<Color>(
                    (states) {
                      if (states.contains(MaterialState.hovered)) {
                        return Colors.orange;
                      } else if (states.contains(MaterialState.pressed)) {
                        return Colors.red;
                      }
                      return Colors.amber;
                    },
                  ),
                ),
              ),
            ],
          ),
        ),
      ),
    );
  }
}