vue-element-template实战（六）实现顶部一级菜单，左侧二级及二级以下菜单

总思路：

一、在layout里加了一个Topbar组件，地址为：src/layout/components/Topbar.vue

Topbar.vue代码如下：

<template>
  <div class="top-nav">
    <div class="log">一级导航</div>
    <el-menu
      :active-text-color="variables.menuActiveText"
      :default-active="activeMenu"
      mode="horizontal"
      @select="handleSelect"
    >
      <div v-for="item in routes" :key="item.path" class="nav-item">
        <app-link :to="resolvePath(item)">
          <el-menu-item
            v-if="!item.hidden"
            :index="item.path"
          >{{ item.meta ? item.meta.title : item.children[0].meta.title }}</el-menu-item>
        </app-link>
      </div>
    </el-menu>

    <div class="right-menu">
      <el-dropdown class="avatar-container" trigger="click">
        <div class="avatar-wrapper">
          <img :src="avatar+'?imageView2/1/w/80/h/80'" class="user-avatar">
          <i class="el-icon-caret-bottom" />
        </div>
        <el-dropdown-menu slot="dropdown" class="user-dropdown">
          <router-link to="/">
            <el-dropdown-item>Home</el-dropdown-item>
          </router-link>
          <a href="https://github.com/PanJiaChen/vue-admin-template/" target="_blank">
            <el-dropdown-item>Github</el-dropdown-item>
          </a>
          <a href="https://panjiachen.github.io/vue-element-admin-site/#/" target="_blank">
            <el-dropdown-item>Docs</el-dropdown-item>
          </a>
          <el-dropdown-item divided @click.native="logout">
            <span style="display:block;">Log Out</span>
          </el-dropdown-item>
        </el-dropdown-menu>
      </el-dropdown>
    </div>
  </div>
</template>

<script>
import { mapGetters } from 'vuex'
import AppLink from './Sidebar/Link'
import { constantRoutes } from '@/router'
import variables from '@/styles/variables.scss'
import { isExternal } from '@/utils/validate'

export default {
  name: 'Topbar',
  components: {
    AppLink
  },
  data() {
    return {
      routes: constantRoutes
    }
  },
  computed: {
    activeMenu() {
      const route = this.$route
      const { meta, path } = route
      // if set path, the sidebar will highlight the path you set
      if (meta.activeMenu) {
        return meta.activeMenu
      }
      // 如果是首页，首页高亮
      if (path === '/dashboard') {
        return '/'
      }
      // 如果不是首页，高亮一级菜单
      const activeMenu = '/' + path.split('/')[1]
      return activeMenu
    },
    variables() {
      return variables
    },
    sidebar() {
      return this.$store.state.app.sidebar
    },
    ...mapGetters(['avatar'])
  },
  mounted() {
    this.initCurrentRoutes()
  },
  methods: {
    // 通过当前路径找到二级菜单对应项，存到store，用来渲染左侧菜单
    initCurrentRoutes() {
      const { path } = this.$route
      let route = this.routes.find(
        item => item.path === '/' + path.split('/')[1]
      )
      // 如果找不到这个路由，说明是首页
      if (!route) {
        route = this.routes.find(item => item.path === '/')
      }
      this.$store.commit('permission/SET_CURRENT_ROUTES', route)
      this.setSidebarHide(route)
    },
    // 判断该路由是否只有一个子项或者没有子项，如果是，则在一级菜单添加跳转路由
    isOnlyOneChild(item) {
      if (item.children && item.children.length === 1) {
        return true
      }
      return false
    },
    resolvePath(item) {
      // 如果是个完成的url直接返回
      if (isExternal(item.path)) {
        return item.path
      }
      // 如果是首页，就返回重定向路由
      if (item.path === '/') {
        const path = item.redirect
        return path
      }

      // 如果有子项，默认跳转第一个子项路由
      let path = ''
      /**
       * item 路由子项
       * parent 路由父项
       */
      const getDefaultPath = (item, parent) => {
        // 如果path是个外部链接（不建议），直接返回链接，存在个问题：如果是外部链接点击跳转后当前页内容还是上一个路由内容
        if (isExternal(item.path)) {
          path = item.path
          return
        }
        // 第一次需要父项路由拼接，所以只是第一个传parent
        if (parent) {
          path += (parent.path + '/' + item.path)
        } else {
          path += ('/' + item.path)
        }
        // 如果还有子项，继续递归
        if (item.children) {
          getDefaultPath(item.children[0])
        }
      }

      if (item.children) {
        getDefaultPath(item.children[0], item)
        return path
      }

      return item.path
    },
    handleSelect(key, keyPath) {
      // 把选中路由的子路由保存store
      const route = this.routes.find(item => item.path === key)
      this.$store.commit('permission/SET_CURRENT_ROUTES', route)
      this.setSidebarHide(route)
    },
    // 设置侧边栏的显示和隐藏
    setSidebarHide(route) {
      if (!route.children || route.children.length === 1) {
        this.$store.dispatch('app/toggleSideBarHide', true)
      } else {
        this.$store.dispatch('app/toggleSideBarHide', false)
      }
    },
    async logout() {
      await this.$store.dispatch('user/logout')
      this.$router.push(`/login?redirect=${this.$route.fullPath}`)
    }
  }
}
</script>

二、修改src/layout/index.vue

<template>
  <div :class="classObj" class="app-wrapper">
    <topbar />  <!-- 此处增加topbar-->
    <div v-if="device==='mobile'&&sidebar.opened" class="drawer-bg" @click="handleClickOutside" />
    <!-- 侧边栏展示的li列表-->
    <sidebar class="sidebar-container" />
    <div class="main-container">
      <div :class="{'fixed-header':fixedHeader}">
        <!-- 导航 -->
        <navbar />
      </div>
      <tags-view />  <!-- 此处增加tag-->
      <!-- 主体部分 -->
      <app-main />
    </div>
  </div>
</template>

import { Navbar, Sidebar, AppMain, TagsView ,Topbar } from './components'

  components: {
    Navbar,
    Sidebar,
    AppMain,
    TagsView,
    Topbar
  },

.app-wrapper {
    @include clearfix;
    position: relative;
    //height: 100%;
    height: $contentHeight;
     100%;
    &.mobile.openSidebar{
      position: fixed;
      top: 0;
    }
  }

三、修改src/styles/variables.scss

$sideBarWidth: 210px;
$topBarHeight: 56px;
$contentHeight: calc(100vh - 56px);

四、新增src/store/modules/permission.js

import { constantRoutes } from '@/router'

const state = {
  routes: [],
  addRoutes: [],
  currentRoutes: {}
}

const mutations = {
  SET_ROUTES: (state, routes) => {
    state.addRoutes = routes
    state.routes = constantRoutes.concat(routes)
  },
  SET_CURRENT_ROUTES: (state, routes) => {
    state.currentRoutes = routes
  }
}

export default {
  namespaced: true,
  state,
  mutations
}

五、修改src/store/index.js

import Vue from 'vue'
import Vuex from 'vuex'
import getters from './getters'
import app from './modules/app'
import settings from './modules/settings'
import user from './modules/user'
import tagsView from './modules/tagsView'
import permission from './modules/permission'  //新增

Vue.use(Vuex)

const store = new Vuex.Store({
  modules: {
    app,
    settings,
    tagsView,
    user,
    permission   //新增
  },
  getters
})

export default store

六、

src/store/modules/permission.js