pmu_flutter/lec1/lib/main.dart

import 'dart:math';

import 'package:flutter/material.dart';

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

class MyApp extends StatelessWidget {
  const MyApp({super.key});

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'My Test App',
      debugShowCheckedModeBanner: false,
      theme: ThemeData(
        colorScheme: ColorScheme.fromSeed(seedColor: Colors.deepPurple),
        useMaterial3: true,
      ),
      home: const MyHomePage(title: 'My Test App'),
    );
  }
}

class MyHomePage extends StatefulWidget {
  const MyHomePage({super.key, required this.title});

  final String title;

  @override
  State<MyHomePage> createState() => _MyHomePageState();
}

class _MyHomePageState extends State<MyHomePage> {
  int _counter = 0;
  Color _color = Colors.orangeAccent;
  Color _fcolor = Colors.black;

  void _incrementCounter() {
    setState(() {
      _counter++;
      _color = Color((Random().nextDouble() * 0xFFFFFF).toInt()).withOpacity(1);
      _fcolor =
          (_color.computeLuminance() <= 0.3) ? Colors.white : Colors.black;
    });
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        backgroundColor: _color,
        foregroundColor: _fcolor,
        title: Text(widget.title),
      ),
      body: Center(
        child: Column(
          mainAxisAlignment: MainAxisAlignment.center,
          children: <Widget>[
            const Text(
              'You have pushed the button this many times:',
            ),
            Text(
              '$_counter',
              style: Theme.of(context).textTheme.headlineMedium,
            ),
            Visibility(
              visible: _counter > 10,
              child: Text(
                'Why are you clicking?',
                style: Theme.of(context).textTheme.headlineMedium,
              ),
            )
          ],
        ),
      ),
      floatingActionButton: FloatingActionButton(
        backgroundColor: _color,
        foregroundColor: _fcolor,
        onPressed: _incrementCounter,
        tooltip: 'Increment',
        child: const Icon(Icons.add),
      ),
    );
  }
}