[flutter] StatelessWidget / StatefulWidget 실습

StatelessWidget 실습

import 'package:flutter/material.dart';
 
void main() {
  runApp(MyApp());
}
 
class MyApp extends StatelessWidget {
  // This widget is the root of your application.
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      theme: ThemeData(
        primarySwatch: Colors.blue,
        visualDensity: VisualDensity.adaptivePlatformDensity,
      ),
      home: Scaffold(
        appBar: AppBar(
          title:Text('Hello World'),
        ),
        body: Text(
          'Hello World',
          style: TextStyle(fontSize: 40),
        ),
      )
    );
  }
}

stless의 경우 home에 바로 작성이 가능하지만, 보통 가독성을 위해 별도의 클래스로 분리함.

 

//별도의 클래스로 분리한 경우. 작동은 위와 동일
 
import 'package:flutter/material.dart';
 
//앱 시작 부분
void main() {
  runApp(MyApp());
}
 
class MyApp extends StatelessWidget {
  // This widget is the root of your application.
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      theme: ThemeData(
        primarySwatch: Colors.blue,
        visualDensity: VisualDensity.adaptivePlatformDensity,
      ),
      home: MyHomePage(),
    );
  }
}
 
class MyHomePage extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title:Text('Hello World'),
      ),
      body: Text(
        'Hello World',
        style: TextStyle(fontSize: 40),
      ),
    );
  }
}

 

 

 

StatefulWidget 실습

버튼을 누르면 글자가 변경되는 예제.

import 'package:flutter/material.dart';
 
//앱 시작 부분
void main() {
  runApp(MyApp());
}
 
class MyApp extends StatelessWidget {
  // This widget is the root of your application.
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      theme: ThemeData(
        primarySwatch: Colors.blue,
        visualDensity: VisualDensity.adaptivePlatformDensity,
      ),
      home: MyHomePage(),
    );
  }
}
 
class MyHomePage extends StatefulWidget {
  @override
  _MyHomePageState createState() => _MyHomePageState();
}
 
class _MyHomePageState extends State<MyHomePage> {
  var _text = "Wow";
 
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text('Hello world'),
      ),
      body: Text(
        _text,
        style: TextStyle(fontSize: 40),
      ),
      floatingActionButton: FloatingActionButton(
        onPressed: (){
          setState(() {
            _text = "hello!";
          });
        },
        child: Icon(Icons.wb_sunny),
      ),
    );
  }
}