quiz.dart

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

QuestionBank questionBank = QuestionBank();

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

class Quizzler extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      home: Scaffold(
        backgroundColor: Colors.grey.shade900,
        body: SafeArea(
          child: Padding(
            padding: EdgeInsets.symmetric(horizontal: 10.0),
            child: QuizPage(),
          ),
        ),
      ),
    );
  }
}

class QuizPage extends StatefulWidget {
  @override
  _QuizPageState createState() => _QuizPageState();
}

class _QuizPageState extends State<QuizPage> {
  List<Icon> scoreKeeper = [];

  void checkAnswer(bool userAnswer) {
    bool correctAnswer = questionBank.getCorrectAnswer();

    setState(() {
      if (userAnswer == correctAnswer) {
        scoreKeeper.add(
          Icon(
            Icons.check,
            color: Colors.green,
          ),
        );
      } else {
        scoreKeeper.add(
          Icon(
            Icons.close,
            color: Colors.red,
          ),
        );
      }
      questionBank.nextQuestion();
    });
  }

  @override
  Widget build(BuildContext context) {
    return Column(
      mainAxisAlignment: MainAxisAlignment.spaceBetween,
      crossAxisAlignment: CrossAxisAlignment.stretch,
      children: <Widget>[
        Expanded(
          flex: 5,
          child: QuestionText(),
        ),
        Expanded(
          child: buildAnswerButton(
            buttonColour: Colors.green,
            buttonText: 'True',
            userAnswer: true,
          ),
        ),
        Expanded(
            child: buildAnswerButton(
          buttonColour: Colors.red,
          buttonText: 'False',
          userAnswer: false,
        )),
        Row(
          children: scoreKeeper,
        ),
      ],
    );
  }

 // Refactored as Method
  Widget buildAnswerButton({
    Color buttonColour,
    String buttonText,
    bool userAnswer,
  }) {
    return Padding(
      padding: EdgeInsets.all(15.0),
      child: FlatButton(
        textColor: Colors.white,
        color: buttonColour,
        child: Text(
          buttonText,
          style: TextStyle(
            color: Colors.white,
            fontSize: 20.0,
          ),
        ),
        onPressed: () {
          //The user picked true.
          checkAnswer(userAnswer);
        },
      ),
    );
  }
}

//Refactored as Widget
class QuestionText extends StatelessWidget {
  const QuestionText({
    Key key,
  }) : super(key: key);

  @override
  Widget build(BuildContext context) {
    return Padding(
      padding: EdgeInsets.all(10.0),
      child: Center(
        child: Text(
          questionBank.getQuestionText(),
          textAlign: TextAlign.center,
          style: TextStyle(
            fontSize: 25.0,
            color: Colors.white,
          ),
        ),
      ),
    );
  }
}