main.dart

import 'dart:math';

import 'package:flutter/material.dart';

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

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

  // This widget is the root of your application.
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      theme: ThemeData(
        // This is the theme of your application.
        //
        // Try running your application with "flutter run". You'll see the
        // application has a blue toolbar. Then, without quitting the app, try
        // changing the primarySwatch below to Colors.green and then invoke
        // "hot reload" (press "r" in the console where you ran "flutter run",
        // or simply save your changes to "hot reload" in a Flutter IDE).
        // Notice that the counter didn't reset back to zero; the application
        // is not restarted.
        primarySwatch: Colors.blue,
      ),
      home: const MyHomePage(title: 'Flutter Demo Home Page'),
    );
  }
}

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

  // This widget is the home page of your application. It is stateful, meaning
  // that it has a State object (defined below) that contains fields that affect
  // how it looks.

  // This class is the configuration for the state. It holds the values (in this
  // case the title) provided by the parent (in this case the App widget) and
  // used by the build method of the State. Fields in a Widget subclass are
  // always marked "final".

  final String title;

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

class _MyHomePageState extends State<MyHomePage> {
  int _counter = 0;
  Color? _backgroundColor;

  void _incrementCounter() {
    setState(() {
      // This call to setState tells the Flutter framework that something has
      // changed in this State, which causes it to rerun the build method below
      // so that the display can reflect the updated values. If we changed
      // _counter without calling setState(), then the build method would not be
      // called again, and so nothing would appear to happen.
      _counter++;
      _changeBackgroundcolor();
    });
  }

  void _decrementCounter() {
    if (_counter == 0) return;

    setState(() {
      _counter--;
      _changeBackgroundcolor();
    });
  }

  void _changeBackgroundcolor() {
    _backgroundColor = Color.fromRGBO(
      Random().nextInt(255),
      Random().nextInt(255),
      Random().nextInt(255),
      1.0,
    );
  }

  @override
  void initState() {
    super.initState();
    debugPrint('Estado iniciado: Só é chamado uma vez por inicialização.');
  }

  @override
  void didChangeDependencies() {
    super.didChangeDependencies();
    debugPrint(
        'Dependências é alteradas: Só é chamado quando uma dependência muda, ou na primeira vez que é iniciado o estado, após o initState.');
  }

  @override
  void didUpdateWidget(covariant MyHomePage oldWidget) {
    super.didUpdateWidget(oldWidget);
    debugPrint(
        'Widget atualizado, estado atualizado: Sempre que é atualizado o widget dono deste estado é invococado este método. Podem ser comparadas as propriedades do oldWidget com o widget atual.');
  }

  @override
  void dispose() {
    super.dispose();
    debugPrint(
        'Widget destruído: Só é chamado uma vez, quando o widget é destruído e, correspondentemente, o seu estado.');
  }

  @override
  Widget build(BuildContext context) {
    // This method is rerun every time setState is called, for instance as done
    // by the _incrementCounter method above.
    //
    // The Flutter framework has been optimized to make rerunning build methods
    // fast, so that you can just rebuild anything that needs updating rather
    // than having to individually change instances of widgets.
    return Scaffold(
      backgroundColor: _backgroundColor,
      appBar: AppBar(
        // Here we take the value from the MyHomePage object that was created by
        // the App.build method, and use it to set our appbar title.
        title: Text(widget.title),
      ),
      body: Center(
        // Center is a layout widget. It takes a single child and positions it
        // in the middle of the parent.
        child: Column(
          // Column is also a layout widget. It takes a list of children and
          // arranges them vertically. By default, it sizes itself to fit its
          // children horizontally, and tries to be as tall as its parent.
          //
          // Invoke "debug painting" (press "p" in the console, choose the
          // "Toggle Debug Paint" action from the Flutter Inspector in Android
          // Studio, or the "Toggle Debug Paint" command in Visual Studio Code)
          // to see the wireframe for each widget.
          //
          // Column has various properties to control how it sizes itself and
          // how it positions its children. Here we use mainAxisAlignment to
          // center the children vertically; the main axis here is the vertical
          // axis because Columns are vertical (the cross axis would be
          // horizontal).
          mainAxisAlignment: MainAxisAlignment.center,
          children: <Widget>[
            FlutterLogo(
              size: _counter >= 10 ? 200.0 : 0.0,
            ),
            // Outra maneira de inserir o widget com base na condição. Ao contrário do exemplo anterior, o widget aqui só é
            // inserido mesmo quando a condição é válida, enquanto que no outro caso apenas muda o tamanho de 0 até 200 com base na condição.
            /*
            if(_counter >= 10) const FlutterLogo(
              size:200.0,
            ),*/
            Text(
              '$_counter',
              style: Theme.of(context).textTheme.headline4,
            ),
            ElevatedButton(
                onPressed: () {
                  setState(() {
                    _counter = 0;
                  });
                },
                child: Text("Reset")),
          ],
        ),
      ),
      floatingActionButton: Row(
        mainAxisAlignment: MainAxisAlignment.spaceBetween,
        children: [
          Padding(
            padding: const EdgeInsets.only(left: 30),
            child: FloatingActionButton(
              onPressed: _decrementCounter,
              tooltip: 'Decrement',
              child: const Icon(Icons.remove),
            ),
          ),
          FloatingActionButton(
            onPressed: _incrementCounter,
            tooltip: 'Increment',
            child: const Icon(Icons.add),
          ),
        ],
      ), // This trailing comma makes auto-formatting nicer for build methods.
    );
  }
}