从0开始手把手教你使用React Hooks开发答题App

Posted 豆约翰

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项目演示地址

项目源码

项目源码


视频教程





项目代码结构

前言

React 框架的优雅不言而喻,组件化的编程思想使得React框架开发的项目代码简洁,易懂,但早期 React 类组件的写法略显繁琐。React Hooks 是 React 16.8 发布以来最吸引人的特性之一,她简化了原有代码的编写,是未来 React 应用的主流写法。

在本项目中,会用到以下知识点:

  • React 组件化设计思想

  • React State 和 Props

  • React 函数式组件的使用

  • React Hooks useState 的使用

  • React Hooks useEffect 的使用

  • React 使用 Axios 请求远程接口获取问题及答案

  • React 使用Bootstrap美化界面

Hello React

(1)安装node.js     官网链接

(2)安装vscode  官网链接

(3)安装 creat-react-app 功能组件,该组件可以用来初始化一个项目, 即按照一定的目录结构,生成一个新项目。打开cmd 窗口 输入:

npm install --g create-react-app
npm install --g yarn

(-g 代表全局安装)

如果安装失败或较慢。需要换源,可以使用淘宝NPM镜像,设置方法为:

npm config set registry https://registry.npm.taobao.org

设置完成后,重新执行

npm install --g create-react-app
npm install --g yarn

 

(4)在你想创建项目的目录下  例如 D:/project/ 打开cmd命令 输入  

create-react-app react-exam

去使用creat-react-app命令创建名字是react-exam的项目

安装完成后,移至新创建的目录并启动项目

cd react-exam
yarn start

一旦运行此命令,localhost:3000新的React应用程序将弹出一个新窗口。从0开始手把手教你使用React Hooks开发答题App

项目目录结构

右键react-exam目录,使用vscode打开该目录。react-exam项目目录中有一个/public和/src目录,以及node_modules,.gitignore,README.md,和package.json。

从0开始手把手教你使用React Hooks开发答题App

在目录/public中,重要文件是index.html,其中一行代码最重要

<div id="root"></div>

该div做为我们整个应用的挂载点

/src目录将包含我们所有的React代码。

要查看环境如何自动编译和更新您的React代码,请找到文件/src/App.js将其中的

        <a
        className="App-link"
        href="https://reactjs.org"
        target="_blank"
        rel="noopener noreferrer"
      >
        Learn React
      </a>

修改为

        <a
        className="App-link"
        href="https://reactjs.org"
        target="_blank"
        rel="noopener noreferrer"
      >
        和豆约翰 Learn React
      </a>

保存文件后,您会注意到localhost:3000编译并刷新了新数据。从0开始手把手教你使用React Hooks开发答题App

React-Exam项目实战

1. 首页制作

1.安装项目依赖,在package.json中添加:

  "dependencies": {
"@testing-library/jest-dom": "^4.2.4",
"@testing-library/react": "^9.3.2",
"@testing-library/user-event": "^7.1.2",
"react": "^16.13.1",
"react-dom": "^16.13.1",
"react-scripts": "3.4.1",
"axios": "^0.19.2",
"bootstrap": "^4.5.0",
"he": "^1.2.0",
"react-loading": "^2.0.3",
"reactstrap": "^8.4.1"
},

执行命令:

yarn install

修改index.js,导入bootstrap样式

import "bootstrap/dist/css/bootstrap.min.css";

修改App.css代码

html {
width: 80%;
margin-left: 10%;
margin-top: 2%;
}

.ansButton {
margin-right: 4%;
margin-top: 4%;
}

修改App.js,引入Quiz组件

import React from 'react';
import './App.css'
import { Quiz } from './Exam/Quiz';

function App() {
return (
<div className = 'layout'>
<Quiz></Quiz>
</div>
);
}

export default App;

在项目src目录下新增Exam目录,Exam目录中新建Quiz.js

Quiz组件的定义如下:Quiz.js,引入开始页面组件Toggle。

import React, { useState } from "react";
import { Toggle } from "./Toggle";
export const Quiz = () => {
const [questionData, setQuestionData] = useState([]);
const questions = questionData.map(({ question }) => [question]);
const answers = questionData.map(({ incorrect_answers, correct_answer }) =>
[correct_answer, incorrect_answers].flat()
);
return (
<>
<Toggle
setQuestionData={setQuestionData}
/>
</>
);
};

Toggle.js,点击开始按钮,通过axios访问远程接口,获得题目及答案。

import React from "react";
import axios from "axios";
import ToggleHeader from "./ToggleHeader";
import {
Button,
Form,
} from "reactstrap";

export const Toggle = ({
setQuestionData,
}) => {
const getData = async () => {
try {
const incomingData = await axios.get(
`https://opentdb.com/api.php?amount=10&category=18&difficulty=easy&type=multiple`
);
setQuestionData(incomingData.data.results);
} catch (err) {
console.error(err);
}
};

return (
<>
<ToggleHeader />
<Form
onSubmit={(e) => {
e.preventDefault();
getData();
}}
>
<Button color="primary">开始</Button>
</Form>
</>
);
};

ToggleHeader.js

import React from "react";
import { Jumbotron, Container} from "reactstrap";

export default function ToggleHeader() {
return (
<Jumbotron fluid>
<Container fluid>
<h1 className="display-4">计算机知识小测验</h1>
</Container>
</Jumbotron>
);
}

https://opentdb.com/api.php接口返回的json数据格式为

{
"response_code": 0,
"results": [{
"category": "Science: Computers",
"type": "multiple",
"difficulty": "easy",
"question": "The numbering system with a radix of 16 is more commonly referred to as ",
"correct_answer": "Hexidecimal",
"incorrect_answers": ["Binary", "Duodecimal", "Octal"]
}, {
"category": "Science: Computers",
"type": "multiple",
"difficulty": "easy",
"question": "This mobile OS held the largest market share in 2012.",
"correct_answer": "iOS",
"incorrect_answers": ["android", "BlackBerry", "Symbian"]
}, {
"category": "Science: Computers",
"type": "multiple",
"difficulty": "easy",
"question": "How many values can a single byte represent?",
"correct_answer": "256",
"incorrect_answers": ["8", "1", "1024"]
}, {
"category": "Science: Computers",
"type": "multiple",
"difficulty": "easy",
"question": "In computing, what does MIDI stand for?",
"correct_answer": "Musical Instrument Digital Interface",
"incorrect_answers": ["Musical Interface of Digital Instruments", "Modular Interface of Digital Instruments", "Musical Instrument Data Interface"]
}, {
"category": "Science: Computers",
"type": "multiple",
"difficulty": "easy",
"question": "In computing, what does LAN stand for?",
"correct_answer": "Local Area Network",
"incorrect_answers": ["Long Antenna Node", "Light Access Node", "Land Address Navigation"]
}]
}

程序运行效果:从0开始手把手教你使用React Hooks开发答题App当前项目目录结构为:从0开始手把手教你使用React Hooks开发答题App

2. 问题展示页面

Quiz.js,新增toggleView变量用来切换视图。

  const [toggleView, setToggleView] = useState(true);

Quiz.js,其中Question和QuestionHeader 组件,参见后面。

import { Question } from "./Question";
import { Jumbotron } from "reactstrap";
import QuestionHeader from "./QuestionHeader";

...
export const Quiz = () => {
var [index, setIndex] = useState(0);
const [questionData, setQuestionData] = useState([]);
...
return (
<>
{toggleView && (
<Toggle
setIndex={setIndex}
setQuestionData={setQuestionData}
setToggleView={setToggleView}
/>
)}
{!toggleView &&
(
<Jumbotron>
<QuestionHeader
setToggleView={setToggleView}
/>
<Question question={questions[index]} />
</Jumbotron>
)}
</>
);

使用index控制题目索引

var [index, setIndex] = useState(0);

修改Toggle.js获取完远程数据,通过setToggleView(false);切换视图。

export const Toggle = ({
setQuestionData,
setToggleView,
setIndex,
}) => {

...

return (
<>
<ToggleHeader />
<Form
onSubmit={(e) => {
e.preventDefault();
getData();
setToggleView(false);
setIndex(0);
}}
>
<Button color="primary">开始</Button>
</Form>
</>
);
};

QuestionHeader.js代码:同样的,点击 返回首页按钮 setToggleView(true),切换视图。

import React from "react";
import { Button } from "reactstrap";
export default function QuestionHeader({ setToggleView, category }) {
return (
<>
<Button color="link" onClick={() => setToggleView(true)}>
返回首页
</Button>
</>
);
}

Question.js代码接受父组件传过来的question对象,并显示。其中he.decode是对字符串中的特殊字符进行转义。

import React from "react";
import he from "he";
export const Question = ({ question }) => {
// he is a oddly named library that decodes html into string values

var decode = he.decode(String(question));

return (
<div>
<hr className="my-2" />
<h1 className="display-5">
{decode}
</h1>
<hr className="my-2" />
<br />
</div>
);
};

程序运行效果:首页从0开始手把手教你使用React Hooks开发答题App点击开始后,显示问题:从0开始手把手教你使用React Hooks开发答题App

当前项目目录结构为:从0开始手把手教你使用React Hooks开发答题App

3. 加载等待动画

新增LoadingSpin.js

import React from "react";
import { Spinner } from "reactstrap";
export default function LoadingSpin() {
return (
<>
<Spinner type="grow" color="primary" />
<Spinner type="grow" color="secondary" />
<Spinner type="grow" color="success" />
<Spinner type="grow" color="danger" />
</>
);
}

修改Quiz.js

import LoadingSpin from "./LoadingSpin";

export const Quiz = () => {

const [isLoading, setLoading] = useState(false);


return (
<>
{toggleView && (
<Toggle
...
setLoading={setLoading}
/>
)}
{!toggleView &&
(isLoading ? (
<LoadingSpin />
) :
(
...
))}
</>
);
};

修改Toggle.js

export const Toggle = ({
...
setLoading,
}) => {
const getData = async () => {
try {
setLoading(true);
const incomingData = await axios.get(
`https://opentdb.com/api.php?amount=10&category=18&difficulty=easy&type=multiple`
);
setQuestionData(incomingData.data.results);
setLoading(false);
} catch (err) {
console.error(err);
}
};

...
};

运行效果:从0开始手把手教你使用React Hooks开发答题App目前代码结构:从0开始手把手教你使用React Hooks开发答题App

4. 实现下一题功能

新增Answer.js,用户点击下一题按钮,修改index,触发主界面刷新,显示下一题:

import React from "react";
import { Button } from "reactstrap";

export const Answer = ({ setIndex, index }) => {
function answerResult() {
setIndex(index + 1);
}

return (
<Button className="ansButton" onClick={answerResult}>
下一题
</Button>
);
};

修改Quiz.js,添加Answer组件:

import { Answer } from "./Answer";
...
{!toggleView &&
(isLoading ? (
<LoadingSpin />
) :
(
<Jumbotron>
...
<Answer
setIndex={setIndex}
index={index}
/>
</Jumbotron>

))}

运行效果:从0开始手把手教你使用React Hooks开发答题App点击下一题:从0开始手把手教你使用React Hooks开发答题App


5. 实现选项展示

新增AnswerList.js。通过属性answers传进来的选项列表,需要被打乱顺序(shuffle )

import React from "react";
import { Answer } from "./Answer";

export const AnswerList = ({ answers, index, setIndex }) => {
if (answers) var correctAns = answers[0];

const shuffle = (array) => {
return array.sort(() => Math.random() - 0.5);
};
const arrayCheck = (arg) => {
return Array.isArray(arg) ? arg : [];
};

return (
<>
{shuffle(arrayCheck(answers)).map((text,ind) => (
<Answer
text={text}
correct={correctAns}
setIndex={setIndex}
index={index}
key={ind}
/>
))}
</>
);
};

修改Answer.js

import React from "react";
import he from "he";
import { Button } from "reactstrap";
export const Answer = ({ text, correct, setIndex, index }) => {
function answerResult() {
setIndex(index + 1);
}


var decode = he.decode(String(text));

return (
<Button className="ansButton" onClick={answerResult}>
{decode}
</Button>
);
};

修改Quiz.js

// import { Answer } from "./Answer";
import { AnswerList } from "./AnswerList";


export const Quiz = () => {
...
return (
<>
...
{!toggleView &&
(isLoading ? (
<LoadingSpin />
) :
(
...
<AnswerList
answers={answers[index]}
index={index}
setIndex={setIndex}
/>
</Jumbotron>

))}
</>
);
};

运行效果:项目结构:

6. 记录用户成绩

修改quiz.js,添加setResult,并传递给AnswerList

export const Quiz = () => {

var [result, setResult] = useState(null);
...
return (
<>
...
{!toggleView &&
(isLoading ? (
<LoadingSpin />
) :
(
<Jumbotron>
...
<AnswerList
answers={answers[index]}
index={index}
setIndex={setIndex}
setResult={setResult}
/>
</Jumbotron>

))}
</>
);
};

修改AnswerList.js,传递setResult

import React from "react";
import { Answer } from "./Answer";

export const AnswerList = ({ answers, index,setResult, setIndex }) => {
...

return (
<>
{shuffle(arrayCheck(answers)).map((text,ind) => (
<Answer
text={text}
correct={correctAns}
setIndex={setIndex}
setResult={setResult}
index={index}
key={ind}
/>
))}
</>
);
};

修改Answer.js,用户点击选项,回调setResult,通知Quiz组件,本次选择是对是错。

import React from "react";
import { Button } from "reactstrap";
import he from 'he'


export const Answer = ({ text, correct, setResult,setIndex, index }) => {
function answerResult() {
setIndex(index + 1);
correct === text ? setResult(true) : setResult(false);
}

var decode = he.decode(String(text));

return (
<Button className="ansButton" onClick={answerResult}>
{decode}
</Button>
);
};

修改Quiz.js,放一个隐藏的GameOver组件,每当index发生变化的时候,触发GameOver中的useEffect代码,累计用户答对题目的数目(setRight)

import GameOver from "./GameOver";

export const Quiz = () => {

const [right, setRight] = useState(0);
const [gameIsOver, setGameOver] = useState(false);


return (
<>
{toggleView && (
<Toggle
setIndex={setIndex}
setQuestionData={setQuestionData}
setToggleView={setToggleView}
setLoading={setLoading}
/>
)}
{!toggleView &&
(isLoading ? (
<LoadingSpin />
) :
(
<Jumbotron>
<QuestionHeader
setToggleView={setToggleView}
/>
<Question question={questions[index]} />
<AnswerList
answers={answers[index]}
index={index}
setIndex={setIndex}
setResult={setResult}
/>
</Jumbotron>
))}
<GameOver
right={right}
setRight={setRight}
quizLength={questions.length}
setGameOver={setGameOver}
result={result}
index={index}
/>
</>
);
};

新增GameOver.js组件,当index === quizLength && index时,setGameOver(true)设置游戏结束,显示用户得分。

import React, { useEffect } from "react";

export default function GameOver({
right,
setRight,
setGameOver,
index,
quizLength,
result,
}) {
useEffect(() => {
if (result === true) {
setRight(right + 1);
}

if (index === quizLength && index) {
setGameOver(true);
}
}, [index]);

return <div></div>;
}

7. 游戏结束,展示用户得分

新增ScoreBoard.js

import React from "react";

export const ScoreBoard = ({ finalScore, right }) => {
// if index === 0 then right === 0 --> this way when index is reset in toggle so is right answers
const scoreFormatted = score => {
if (score === 1) {
return 100;
} else if (score === 0) {
return 0;
} else {
return score.toFixed(2) * 100;
}
}

return (
<>
<>
<h1 className="display-4">Correct Answers: {right}</h1>
<hr className="my-2" />

<h1 className="display-4">
Final Score: %{scoreFormatted(finalScore)}
</h1>

<hr className="my-2" />
</>
<p>谢谢使用 </p>
</>
);
};

ScoreHeader.js

import React from "react";
import { Button } from "reactstrap";
export default function ScoreHeader({ setGameOver, setToggleView }) {
return (
  <Button
    color="link"
    onClick={() => {
      setGameOver(false);
      setToggleView(true);
    }}
  >
    返回首页
  </Button>
);
}

修改Quiz.js,当gameIsOver 变量为true时,显示得分页面。

import { ScoreBoard } from "./ScoreBoard";
import ScoreHeader from "./ScoreHeader";

export const Quiz = () => {

...

return (
  <>

    {!toggleView &&
      !gameIsOver &&
      (isLoading ? (
        <LoadingSpin />
      ) :
      (
        ...
        ))}
           
    {gameIsOver && (
      <Jumbotron>
        <ScoreHeader
          setToggleView={setToggleView}
          setGameOver={setGameOver}
        />
        <ScoreBoard right={right} finalScore={right / index} />
      </Jumbotron>
    )}
     
  ...
  </>
);
};


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