从0开始，手把手教你用Vue开发一个答题App01之项目创建及答题设置页面开发

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