从0开始，手把手教你用Vue开发一个答题App

项目演示

项目源码

教程说明

本教程适合对Vue基础知识有一点了解，但不懂得综合运用，还未曾使用Vue从头开发过一个小型App的读者。本教程不对所有的Vue知识点进行讲解，而是手把手一步步从0到1，做出一个完整的小项目。目前网上的教程不是只有零散的知识点讲解；就是抛出一个开源的大项目，初级读者下载下来后，运行起来都很费劲，更谈不上理解这个项目是如何一步步开发出来的了。本教程试图弥补这个空白。

1. 项目初始化

1.1使用 Vue CLI 创建项目

如果你还没有安装 VueCLI，请执行下面的命令安装或是升级：
npm install --global @vue/cli

在命令行中输入以下命令创建 Vue 项目：

vue create vue-quiz

Vue CLI v4.3.1

? Please pick a preset:

> default (babel, eslint)

  Manually select features

default：默认勾选 babel、eslint，回车之后直接进入装包

manually：自定义勾选特性配置，选择完毕之后，才会进入装包

选择第 1 种 default.

安装结束，命令提示你项目创建成功，按照命令行的提示在终端中分别输入：

# 进入你的项目目录

cd vue-quiz

# 启动开发服务

npm run serve

启动成功，命令行中输出项目的 http 访问地址。打开浏览器，输入其中任何一个地址进行访问

如果能看到该页面，恭喜你，项目创建成功了。

1.2 初始目录结构

项目创建好以后，下面我们来了解一下初始目录结构：

1.3 调整初始目录结构，实现游戏设置页面

默认生成的目录结构不满足我们的开发需求，所以需要做一些自定义改动。

这里主要处理下面的内容：

删除初始化的默认文件
新增调整我们需要的目录结构

删除默认示例文件：

src/components/HelloWorld.vue
src/assets/logo.png

修改package.json，添加项目依赖：

 "dependencies": {

    "axios": "^0.19.2",

    "bootstrap": "^4.4.1",

    "bootstrap-vue": "^2.5.0",

    "core-js": "^3.6.5",

    "vue": "^2.6.11",

    "vue-router": "^3.1.5"

  },

  "devDependencies": {

    "@vue/cli-plugin-babel": "~4.4.0",

    "@vue/cli-plugin-eslint": "~4.4.0",

    "@vue/cli-plugin-router": "~4.4.0",

    "@vue/cli-service": "~4.4.0",

    "babel-eslint": "^10.1.0",

    "eslint": "^6.7.2",

    "eslint-plugin-vue": "^6.2.2",

    "vue-template-compiler": "^2.6.11"

  },

然后运行yarn install,安装依赖。

修改项目入口文件main.js，引入bootstrap-vue。

import Vue from 'vue'

import App from './App.vue'

import router from './router'

import BootstrapVue from 'bootstrap-vue'

import 'bootstrap/dist/css/bootstrap.css'

import 'bootstrap-vue/dist/bootstrap-vue.css'

Vue.config.productionTip = false

Vue.use(BootstrapVue)

const state = { questions: [] }

new Vue({

  router,

  data: state,

  render: h => h(App)

}).$mount('#app')

定义一个state对象来共享答题数据（答题页面和结果页面共享）

const state = { questions: [] }

src目录下新增eventBus.js消息总线，用来在组件间传递消息，代码如下：

import Vue from 'vue'

const EventBus = new Vue()

export default EventBus

修改App.vue，css样式略，请参考源码。

<template>

  <div id="app" class="bg-light">

    <Navbar></Navbar>

    <b-alert :show="dismissCountdown" dismissible variant="danger" @dismissed="dismissCountdown = 0">

      {{ errorMessage }}

    </b-alert>

    <div class="d-flex justify-content-center">

      <b-card no-body id="main-card" class="col-sm-12 col-lg-4 px-0">

        <router-view></router-view>

      </b-card>

    </div>

  </div>

</template>

<script>

import EventBus from './eventBus'

import Navbar from './components/Navbar'

export default {

  name: 'app',

  components: {

    Navbar

  },

  data() {

    return {

      errorMessage: '',

      dismissSecs: 5,

      dismissCountdown: 0

    }

  },

  methods: {

    showAlert(error) {

      this.errorMessage = error

      this.dismissCountdown = this.dismissSecs

    }

  },

  mounted() {

    EventBus.$on('alert-error', (error) => {

      this.showAlert(error)

    })

  },

  beforeDestroy() {

    EventBus.$off('alert-error')

  }

}

</script>

新增components/Navbar.vue，定义导航部分。

<template>

    <b-navbar id="navbar" class="custom-info" type="dark" sticky>

      <b-navbar-brand id="nav-logo" :to="{ name: 'home' }">Vue-Quiz</b-navbar-brand>

      <b-navbar-nav class="ml-auto">

        <b-nav-item :to="{ name: 'home' }">New Game </b-nav-item>

        <b-nav-item href="#" target="_blank">About</b-nav-item>

      </b-navbar-nav>

    </b-navbar>

</template>

<script>

export default {

  name: 'Navbar'

}

</script>

<style scoped>

</style>

src目录下新增router/index.js，定义首页路由。

import Vue from 'vue'

import VueRouter from 'vue-router'

import MainMenu from '../views/MainMenu.vue'

Vue.use(VueRouter)

const routes = [

  {

    name: 'home',

    path: '/',

    component: MainMenu

  }

]

const router = new VueRouter({

  mode: 'history',

  base: process.env.BASE_URL,

  routes

})

export default router

src下新增views/MainMenu.vue，MainMenu主要包含GameForm组件。

<template>

<div>

  <b-card-header class="custom-info text-white font-weight-bold">New Game</b-card-header>

  <b-card-body class="h-100">

    <GameForm @form-submitted="handleFormSubmitted"></GameForm>

  </b-card-body>

</div>

</template>

<script>

import GameForm from '../components/GameForm'

export default {

  name: 'MainMenu',

  components: {

    GameForm

  },

  methods: {

    /** Triggered by custom 'form-submitted' event from GameForm child component.

     * Parses formData, and route pushes to 'quiz' with formData as query

     * @public

     */

    handleFormSubmitted(formData) {

      const query = formData

      query.difficulty = query.difficulty.toLowerCase()

      this.$router.push({ name: 'quiz', query: query })

    }

  }

}

</script>

新增src/components/GameForm.vue，实现游戏初始设置。

<template>

  <div>

    <LoadingIcon v-if="loading"></LoadingIcon>

    <div v-else>

      <b-form @submit="onSubmit">

        <b-form-group

          id="input-group-number-of-questions"

          label="Select a number"

          label-for="input-number-of-questions"

          class="text-left"

        >

          <b-form-input

            id="input-number-of-questions"

            v-model="form.number"

            type="number"

            :min="minQuestions"

            :max="maxQuestions"

            required

            :placeholder="`Between ${minQuestions} and ${maxQuestions}`"

          ></b-form-input>

        </b-form-group>

        <b-form-group id="input-group-category">

          <b-form-select

            id="input-category"

            v-model="form.category"

            :options="categories"

          ></b-form-select>

        </b-form-group>

        <b-form-group id="input-group-difficulty">

          <b-form-select

            id="input-difficulty"

            v-model="form.difficulty"

            :options="difficulties"

          ></b-form-select>

        </b-form-group>

        <b-form-group id="input-group-type">

          <b-form-select

            id="input-type"

            v-model="form.type"

            :options="types"

          ></b-form-select>

        </b-form-group>

        <b-button type="submit" class="custom-success">Submit</b-button>

      </b-form>

    </div>

  </div>

</template>

<script>

import LoadingIcon from './LoadingIcon'

import axios from 'axios'

export default {

  components: {

    LoadingIcon

  },

  data() {

    return {

      // Form data, tied to respective inputs

      form: {

        number: '',

        category: '',

        difficulty: '',

        type: ''

      },

      // Used for form dropdowns and number input

      categories: [{ text: 'Category', value: '' }],

      difficulties: [{ text: 'Difficulty', value: '' }, 'Easy', 'Medium', 'Hard'],

      types: [

        { text: 'Type', value: '' },

        { text: 'Multiple Choice', value: 'multiple' },

        { text: 'True or False', value: 'boolean'}

      ],

      minQuestions: 10,

      maxQuestions: 20,

      // Used for displaying ajax loading animation OR form

      loading: true

    }

  },

  created() {

    this.fetchCategories()

  },

  methods: {

    fetchCategories() {

      axios.get('https://opentdb.com/api_category.php')

      .then(resp => resp.data)

      .then(resp => {

        resp.trivia_categories.forEach(category => {

          this.categories.push({text: category.name, value: `${category.id}`})

        });

        this.loading = false;

      })

    },

    onSubmit(evt) {

      evt.preventDefault()

       /** Triggered on form submit. Passes form data

        * @event form-submitted

        * @type {number|string}

        * @property {object}

        */

      this.$emit('form-submitted', this.form)

    }

  }

}

</script>

GameForm组件，主要通过axios发起获取全部题目分类请求：

axios.get('https://opentdb.com/api_category.php')

新增src/components/LoadingIcon.vue，在异步请求数据未返回时，渲染等待图标。

<template>

  <div id="loading-icon" class="h-100 d-flex justify-content-center align-items-center">

    <img src="@/assets/ajax-loader.gif" alt="Loading Icon">

  </div>

</template>

<script>

export default {

  name: 'LoadingIcon'

}

</script>

新增src/assets/ajax-loader.gif等待动画文件，请参考项目源码。

1.4 运行项目

yarn run serve

2. 答题页面开发

2.1 修改路由

修改router/index.js：

import Vue from 'vue'

import VueRouter from 'vue-router'

import MainMenu from '../views/MainMenu.vue'

import GameController from '../views/GameController.vue'

Vue.use(VueRouter)

const routes = [

  {

    name: 'home',

    path: '/',

    component: MainMenu

  }, {

    name: 'quiz',

    path: '/quiz',

    component: GameController,

    props: (route) => ({

      number: route.query.number,

      difficulty: route.query.difficulty,

      category: route.query.category,

      type: route.query.type

    })

  }

]

const router = new VueRouter({

  mode: 'history',

  base: process.env.BASE_URL,

  routes

})

export default router

2.2 答题页面

新增views/GameController.vue

本页面是本项目最重要的模块，展示问题，和处理用户提交的答案，简单解析一下：

1.fetchQuestions函数通过请求远程接口获得问题列表。

2.setQuestions保存远程回应的问题列表到本地数组。

3.onAnswerSubmit处理用户提交的选项，调用nextQuestion函数返回下一问题。

<template>

  <div class="h-100">

    <LoadingIcon v-if="loading"></LoadingIcon>

    <Question :question="currentQuestion" @answer-submitted="onAnswerSubmit" v-else></Question>

  </div>

</template>

<script>

import EventBus from '../eventBus'

import ShuffleMixin from '../mixins/shuffleMixin'

import Question from '../components/Question'

import LoadingIcon from '../components/LoadingIcon'

import axios from 'axios'

export default {

  name: 'GameController',

  mixins: [ShuffleMixin],

  props: {

    /** Number of questions */

    number: {

      default: '10',

      type: String,

      required: true

    },

    /** Id of category. Empty string if not included in query */

    category: String,

    /** Difficulty of questions. Empty string if not included in query */

    difficulty: String,

    /** Type of questions. Empty string if not included in query */

    type: String

  },

  components: {

    Question,

    LoadingIcon

  },

  data() {

    return {

      // Array of custom question objects. See setQuestions() for format

      questions: [],

      currentQuestion: {},

      // Used for displaying ajax loading animation OR form

      loading: true

    }

  },

  created() {

    this.fetchQuestions()

  },

  methods: {

    /** Invoked on created()

     * Builds API URL from query string (props).

     * Fetches questions from API.

     * "Validates" return from API and either routes to MainMenu view, or invokes setQuestions(resp).

     * @public

     */

    fetchQuestions() {

      let url = `https://opentdb.com/api.php?amount=${this.number}`

      if (this.category)   url += `&category=${this.category}`

      if (this.difficulty) url += `&difficulty=${this.difficulty}`

      if (this.type)       url += `&type=${this.type}`

      axios.get(url)

        .then(resp => resp.data)

        .then(resp => {

          if (resp.response_code === 0) {

            this.setQuestions(resp)

          } else {

            EventBus.$emit('alert-error', 'Bad game settings. Try another combination.')

            this.$router.replace({ name: 'home' })

          }

        })

    },

    /** Takes return data from API call and transforms to required object setup.

     * Stores return in $root.$data.state.

     * @public

     */

    setQuestions(resp) {

      resp.results.forEach(qst => {

        const answers = this.shuffleArray([qst.correct_answer, ...qst.incorrect_answers])

        const question = {

          questionData: qst,

          answers: answers,

          userAnswer: null,

          correct: null

        }

        this.questions.push(question)

      })

      this.$root.$data.state = this.questions

      this.currentQuestion = this.questions[0]

      this.loading = false

    },

    /** Called on submit.

     * Checks if answer is correct and sets the user answer.

     * Invokes nextQuestion().

     * @public

     */

    onAnswerSubmit(answer) {

      if (this.currentQuestion.questionData.correct_answer === answer) {

        this.currentQuestion.correct = true

      } else {

        this.currentQuestion.correct = false

      }

      this.currentQuestion.userAnswer = answer

      this.nextQuestion()

    },

    /** Filters all unanswered questions,

     * checks if any questions are left unanswered,

     * updates currentQuestion if so,

     * or routes to "result" if not.

     * @public

     */

    nextQuestion() {

      const unansweredQuestions = this.questions.filter(q => !q.userAnswer)

      if (unansweredQuestions.length > 0) {

        this.currentQuestion = unansweredQuestions[0]

      } else {

        this.$router.replace({ name: 'result' })

      }

    }

  }

}

</script>

新增\src\mixins\shuffleMixin.js

打乱问题答案，因为远程返回的答案有规律。mixins是混入的意思，可以混入到我们的某个页面或组件中，补充页面或组件功能，便于复用。

const ShuffleMixin = {

    methods: {

      shuffleArray: (arr) => arr

        .map(a => [Math.random(), a])

        .sort((a, b) => a[0] - b[0])

        .map(a => a[1])

    }

  }

  export default ShuffleMixin

新增src/components/Question.vue

<template>

  <div>

    <QuestionBody :questionData="question.questionData"></QuestionBody>

    <b-card-body class="pt-0">

      <hr>

      <b-form @submit="onSubmit">

        <b-form-group

          label="Select an answer:"

          class="text-left"

        >

          <b-form-radio

            v-for="(ans, index) of question.answers"

            :key="index"

            v-model="answer"

            :value="ans"

          >

            <div v-html="ans"></div>

          </b-form-radio>

        </b-form-group>

        <b-button type="submit" class="custom-success">Submit</b-button>

      </b-form>

    </b-card-body>

  </div>

</template>

<script>

import QuestionBody from './QuestionBody'

export default {

  name: 'Question',

  props: {

    /** Question object containing questionData, possible answers, and user answer information. */

    question: {

      required: true,

      type: Object

    }

  },

  components: {

    QuestionBody

  },

  data() {

    return {

      answer: null

    }

  },

  methods: {

    onSubmit(evt) {

      evt.preventDefault()

      if (this.answer) {

        /** Triggered on form submit. Passes user answer.

        * @event answer-submitted

        * @type {number|string}

        * @property {string}

        */

        this.$emit('answer-submitted', this.answer)

        this.answer = null

      }

    }

  }

}

</script>

新增src/components/QuestionBody.vue

<template>

  <div>

    <b-card-header :class="variant" class="d-flex justify-content-between border-bottom-0">

      <div>{{ questionData.category }}</div>

      <div class="text-capitalize">{{ questionData.difficulty }}</div>

    </b-card-header>

    <b-card-body>

      <b-card-text class="font-weight-bold" v-html="questionData.question"></b-card-text>

    </b-card-body>

  </div>

</template>

<script>

export default {

  name: 'QuestionBody',

  props: {

    /** Object containing question data as given by API. */

    questionData: {

      required: true,

      type: Object

    }

  },

  data() {

    return {

      variants: { easy: 'custom-success', medium: 'custom-warning', hard: 'custom-danger', default: 'custom-info' },

      variant: 'custom-info'

    }

  },

  methods: {

    /** Invoked on mounted().

     * Sets background color of card header based on question difficulty.

     * @public

     */

    setVariant() {

      switch (this.questionData.difficulty) {

        case 'easy':

          this.variant = this.variants.easy

          break

        case 'medium':

          this.variant = this.variants.medium

          break

        case 'hard':

          this.variant = this.variants.hard

          break

        default:

          this.variant = this.variants.default

          break

      }

    }

  },

  mounted() {

    this.setVariant()

  }

}

</script>

<docs>

Simple component displaying question category, difficulty and question text.

Used on both Question component and Answer component.

</docs>

运行：

yarn run serve

启动成功:

如果能看到该页面，恭喜你，项目到此成功了。

2.3 至此项目目录结构

如果你走丢，请下载源码进行对比：

3 实现最终结果展示页面

再次修改router/index.js

import Vue from 'vue'

import VueRouter from 'vue-router'

import MainMenu from '../views/MainMenu.vue'

import GameController from '../views/GameController.vue'

import GameOver from '../views/GameOver'

Vue.use(VueRouter)

const routes = [

  ...

  {

    name: 'result',

    path: '/result',

    component: GameOver

  }

]

...

新增src/views/GameOver.vue：

<template>

  <div class="h-100">

      <b-card-header class="custom-info text-white font-weight-bold">Your Score: {{ score }} / {{ maxScore }}</b-card-header>

    <Answer v-for="(question, index) of questions" :key="index" :question="question"></Answer>

  </div>

</template>

<script>

import Answer from '../components/Answer'

export default {

  name: 'GameOver',

  components: {

    Answer

  },

  data() {

    return {

      questions: [],

      score: 0,

      maxScore: 0

    }

  },

  methods: {

    /** Invoked on created().

     * Grabs data from $root.$data.state.

     * Empties $root.$data.state => This is done to ensure data is cleared when starting a new game.

     * Invokes setScore().

     * @public

     */

    setQuestions() {

      this.questions = this.$root.$data.state || []

      this.$root.$data.state = []

      this.setScore()

    },

    /** Computes maximum possible score (amount of questions * 10)

     * Computes achieved score (amount of correct answers * 10)

     * @public

     */

    setScore() {

      this.maxScore = this.questions.length * 10

      this.score = this.questions.filter(q => q.correct).length * 10

    }

  },

  created() {

    this.setQuestions();

  }

}

</script>

新增src\components\Answer.vue

<template>

  <div>

    <b-card no-body class="answer-card rounded-0">

      <QuestionBody :questionData="question.questionData"></QuestionBody>

      <b-card-body class="pt-0 text-left">

        <hr class="mt-0">

        <b-card-text

          class="px-2"

          v-html="question.questionData.correct_answer"

        >

        </b-card-text>

        <b-card-text

          class="px-2"

          :class="{ 'custom-success': question.correct, 'custom-danger': !question.correct }"

          v-html="question.userAnswer"

        >

        </b-card-text>

      </b-card-body>

    </b-card>

  </div>

</template>

<script>

import QuestionBody from './QuestionBody'

export default {

  name: 'Answer',

  props: {

    /** Question object containing questionData, possible answers, and user answer information. */

    question: {

      required: true,

      type: Object

    }

  },

  components: {

    QuestionBody

  }

}

</script>

<style scoped>

.answer-card >>> .card-header {

  border-radius: 0;

}

</style>

3.1 运行项目

yarn run serve

3.2 项目结构

项目总结

很感谢您和豆约翰走到了这里，至此我们一个小型的Vue项目，全部开发完毕，下一期，豆约翰会带大家见识一个中型的项目，咱们循序渐进，一起加油。

最后

为了将来还能找到我

巴特西