[windows/flutter] 增加套件，Stateful

參考網址

1. pubspec.yaml檔案的dependencies中加入套件english_words: ^3.1.0

dev_dependencies:
  flutter_test:
    sdk: flutter
  english_words: ^3.1.0

2.

import 'package:english_words/english_words.dart';

引入套件

3.

final wordPair = WordPair.random();

final就是個不會改變的回傳值

4.

body: Center(
    child: Text(wordPair.asPascalCase)
)

asPascalCase就是大駝峰

5.

class RandomWordsState extends State<RandomWords> {
  @override
  Widget build(BuildContext context) {
    final wordPair = WordPair.random();
    return Text(wordPair.asPascalCase);
  }
}

class RandomWords extends StatefulWidget{
  @override
  RandomWordsState createState() => RandomWordsState();
}

先看結果
6.

class RandomWordsState extends State<RandomWords> {

你今天要自己創一個組件(stateful)的話，就要產生兩個class，第一個是回傳外觀的State

7.

class RandomWords extends StatefulWidget{
  @override
  RandomWordsState createState() => RandomWordsState();
}

第二個是create state的StatefulWidget
( 等於要用createSate這個方法來執行你自己創的class(做的事情是回傳一個外觀) )
8.

import 'package:flutter/material.dart';
import 'package:english_words/english_words.dart';


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

class MyApp extends StatelessWidget{
  @override
  Widget build(BuildContext context){
    return MaterialApp(
      title: 'My Title',
      home: Scaffold(
        appBar: AppBar(
          title: Text('Bar Title')
        ),
        body: Center(
          child: RandomWords()
        )
      )
    );
  }
}


class RandomWordsState extends State<RandomWords> {
  @override
  Widget build(BuildContext context) {
    final wordPair = WordPair.random();
    return Text(wordPair.asPascalCase);
  }
}

class RandomWords extends StatefulWidget{
  @override
  RandomWordsState createState() => RandomWordsState();
}

完全體