Chapter 59 — Quiz

Level: intermediate Estimated time: 12 h Prerequisites: PART 1A (chapters 01 to 18), PART 1B (chapters 43 to 54), and projects 55 to 58 What you will be able to do by the end: build a complete quiz app — a question bank in JSON embedded in the assets, asynchronous loading, a pure and testable quiz engine, a per-question countdown, immediate visual feedback, animated transitions, a detailed results screen, a persistent best score, and automated tests.

59.0 — Chapter Objectives

By the end of this chapter, you will be able to:

• model a multiple-choice question with a difficulty enum (recap of chapter 11);
• write a defensive fromJson that rejects a malformed question (recap of chapters 13 and 17);
• store a question bank in JSON format in the assets and declare it in pubspec.yaml (recap of chapter 47);
• load a text asset asynchronously with rootBundle.loadString (recap of chapter 15);
• write a quiz engine as a pure class, with no dependency on Flutter;
• display a home screen with a choice of category and number of questions;
• build a readable, reusable question screen;
• write an answer button that changes appearance across five states;
• give immediate visual feedback, green or red, without ever blocking the interface;
• display an explanation after each answer;
• animate a progress bar with TweenAnimationBuilder;
• manage a per-question countdown with Timer.periodic (recap of chapter 45);
• treat time expiration as an answer in its own right;
• chain questions together with an AnimatedSwitcher transition;
• shuffle questions and answers with shuffle, and make that shuffle testable;
• build a results screen with a message tailored to the score;
• display a question-by-question summary;
• persist the best score per category with shared_preferences (recap of chapter 54);
• move all state, timer included, into a ChangeNotifier exposed by provider (recap of chapter 52);
• make the app usable with a screen reader and correct in dark mode (recap of chapter 51);
• write unit tests for the scoring logic and the shuffle.