前言

基本上后台管理系统都需要有多页签的功能，但是因为一些脚手架项目基本都把这个功能给集成好了，导致在学习或者修改的时候不知道该如何下手。今天这篇文章就来聊一聊，vue-element-admin项目是如何实现多页签功能的。

一、效果图

实现之后的效果如下图所示，点击左边的不同的菜单会打开多个页签，并且右键页签可以操作关闭页签。
在这里插入图片描述

二、实现思路

利用Vue的内置组件keepalive和routeLink解决，数据是通过vuex进行管理。

1. 新建 tags-view.js

在…\store\modules文件夹下新建一个tags-view.js，里面定义相关标签新建、关闭的操作方法，代码如下（示例）：

const state = {
  // 用户访问过的页面 就是标签栏导航显示的一个个 tag 数组集合
  visitedViews: [],
  // 实际 keep-alive 的路由。可以在配置路由的时候通过 meta.noCache 来设置是否需要缓存这个路由 默认都缓存。
  cachedViews: []
}

const mutations = {
  // 添加标签
  ADD_VISITED_VIEW: (state, view) => {
    // 如果标签跳转的路由存在就不添加，否则就添加进标签组
    if (state.visitedViews.some(v => v.path === view.path)) return
    state.visitedViews.push(
      Object.assign({}, view, {
        title: view.meta.title || 'no-name'
      })
    )
  },
  // 添加缓存标签
  ADD_CACHED_VIEW: (state, view) => {
    // 已存在缓存就不缓存了
    if (state.cachedViews.includes(view.name)) return
    if (view.meta && !view.meta.noCache) {
      state.cachedViews.push(view.name)
    }
  },
  // 删除选择的标签
  DEL_VISITED_VIEW: (state, view) => {
    for (const [i, v] of state.visitedViews.entries()) {
      if (v.path === view.path) {
        state.visitedViews.splice(i, 1)
        break
      }
    }
  },
  // 删除缓存标签
  DEL_CACHED_VIEW: (state, view) => {
    const index = state.cachedViews.indexOf(view.name)
    index > -1 && state.cachedViews.splice(index, 1)
  },
  // 删除其它标签
  DEL_OTHERS_VISITED_VIEWS: (state, view) => {
    state.visitedViews = state.visitedViews.filter(v => {
      return v.meta.affix || v.path === view.path
    })
  },
  // 删除其它缓存标签
  DEL_OTHERS_CACHED_VIEWS: (state, view) => {
    const index = state.cachedViews.indexOf(view.name)
    if (index > -1) {
      state.cachedViews = state.cachedViews.slice(index, index + 1)
    } else {
      state.cachedViews = []
    }
  },
  // 删除所有标签
  DEL_ALL_VISITED_VIEWS: state => {
    // 过滤出固定的标签，只保留固定标签
    const affixTags = state.visitedViews.filter(tag => tag.meta.affix)
    state.visitedViews = affixTags
  },
  // 删除所有缓存标签
  DEL_ALL_CACHED_VIEWS: state => {
    state.cachedViews = []
  },

  UPDATE_VISITED_VIEW: (state, view) => {
    for (let v of state.visitedViews) {
      if (v.path === view.path) {
        v = Object.assign(v, view)
        break
      }
    }
  },
  // 删除右侧标签
  DEL_RIGHT_VIEWS: (state, view) => {
    const index = state.visitedViews.findIndex(v => v.path === view.path)
    if (index === -1) {
      return
    }
    state.visitedViews = state.visitedViews.filter((item, idx) => {
      if (idx <= index || (item.meta && item.meta.affix)) {
        return true
      }
      const i = state.cachedViews.indexOf(item.name)
      if (i > -1) {
        state.cachedViews.splice(i, 1)
      }
      return false
    })
  },
  // 删除左侧标签
  DEL_LEFT_VIEWS: (state, view) => {
    const index = state.visitedViews.findIndex(v => v.path === view.path)
    if (index === -1) {
      return
    }
    state.visitedViews = state.visitedViews.filter((item, idx) => {
      if (idx >= index || (item.meta && item.meta.affix)) {
        return true
      }
      const i = state.cachedViews.indexOf(item.name)
      if (i > -1) {
        state.cachedViews.splice(i, 1)
      }
      return false
    })
  }
}

const actions = {
  // 新增当前路由标签和标签缓存
  addView({ dispatch }, view) {
    dispatch('addVisitedView', view)
    dispatch('addCachedView', view)
  },
  // 新增当前路由标签
  addVisitedView({ commit }, view) {
    commit('ADD_VISITED_VIEW', view)
  },
  // 新增当前路由标签缓存
  addCachedView({ commit }, view) {
    commit('ADD_CACHED_VIEW', view)
  },
  // 删除当前路由标签和标签缓存
  delView({ dispatch, state }, view) {
    return new Promise(resolve => {
      dispatch('delVisitedView', view)
      dispatch('delCachedView', view)
      resolve({
        visitedViews: [...state.visitedViews],
        cachedViews: [...state.cachedViews]
      })
    })
  },
  // 删除当前路由标签
  delVisitedView({ commit, state }, view) {
    return new Promise(resolve => {
      commit('DEL_VISITED_VIEW', view)
      resolve([...state.visitedViews])
    })
  },
  // 删除当前路由标签缓存
  delCachedView({ commit, state }, view) {
    return new Promise(resolve => {
      commit('DEL_CACHED_VIEW', view)
      resolve([...state.cachedViews])
    })
  },
  // 删除其他路由标签和标签缓存
  delOthersViews({ dispatch, state }, view) {
    return new Promise(resolve => {
      dispatch('delOthersVisitedViews', view)
      dispatch('delOthersCachedViews', view)
      resolve({
        visitedViews: [...state.visitedViews],
        cachedViews: [...state.cachedViews]
      })
    })
  },
  // 删除其他路由标签
  delOthersVisitedViews({ commit, state }, view) {
    return new Promise(resolve => {
      commit('DEL_OTHERS_VISITED_VIEWS', view)
      resolve([...state.visitedViews])
    })
  },
  // 删除其他路由标签缓存
  delOthersCachedViews({ commit, state }, view) {
    return new Promise(resolve => {
      commit('DEL_OTHERS_CACHED_VIEWS', view)
      resolve([...state.cachedViews])
    })
  },
  // 删除所有路由标签和标签缓存
  delAllViews({ dispatch, state }, view) {
    return new Promise(resolve => {
      dispatch('delAllVisitedViews', view)
      dispatch('delAllCachedViews', view)
      resolve({
        visitedViews: [...state.visitedViews],
        cachedViews: [...state.cachedViews]
      })
    })
  },
  // 删除所有路由标签
  delAllVisitedViews({ commit, state }) {
    return new Promise(resolve => {
      commit('DEL_ALL_VISITED_VIEWS')
      resolve([...state.visitedViews])
    })
  },
  // 删除所有路由标签缓存
  delAllCachedViews({ commit, state }) {
    return new Promise(resolve => {
      commit('DEL_ALL_CACHED_VIEWS')
      resolve([...state.cachedViews])
    })
  },

  updateVisitedView({ commit }, view) {
    commit('UPDATE_VISITED_VIEW', view)
  },
  // 删除右侧路由标签缓存
  delRightTags({ commit }, view) {
    return new Promise(resolve => {
      commit('DEL_RIGHT_VIEWS', view)
      resolve([...state.visitedViews])
    })
  },
  // 删除左侧路由标签缓存
  delLeftTags({ commit }, view) {
    return new Promise(resolve => {
      commit('DEL_LEFT_VIEWS', view)
      resolve([...state.visitedViews])
    })
  },
}

export default {
  namespaced: true,
  state,
  mutations,
  actions
}

2. 在Vuex里面引入 tags-view.js

在store 目录下 index.js 文件修改，代码如下（示例）：

import Vue from 'vue'
import Vuex from 'vuex'
...
// 新加
import tagsView from './modules/tags-view'

Vue.use(Vuex)

const store = new Vuex.Store({
  modules: {
   ...
   // 新加
    tagsView
  },
  getters
})

export default store

3. 新建 tabsView 组件

在 layout/components 目录下新建目录 TabsView，在该目录下新建 index.vue 文件，代码如下（示例）：

<template>
  <div id="tags-view-container" class="tags-view-container">
    <!-- 路由标签显示区域（滚动）组件 -->
    <scroll-pane ref="scrollPane" class="tags-view-wrapper" @scroll="handleScroll">
      <router-link
        v-for="tag in visitedViews"
        ref="tag"
        :key="tag.path"
        :class="isActive(tag)?'active':''"
        :to="{ path: tag.path, query: tag.query, fullPath: tag.fullPath }"
        tag="span"
        class="tags-view-item"
        :style="activeStyle(tag)"
        @click.middle.native="!isAffix(tag)?closeSelectedTag(tag):''"
        @contextmenu.prevent.native="openMenu(tag,$event)"
      >
        {{ tag.title }}
        <!-- 这个地方一定要click加个stop阻止，不然会因为事件冒泡一直触发父元素的点击事件，无法跳转另一个路由 -->
        <span v-if="!isAffix(tag)" class="el-icon-close" @click.prevent.stop="closeSelectedTag(tag)" />
      </router-link>
    </scroll-pane>
    <ul v-show="visible" :style="{left:left+'px',top:top+'px'}" class="contextmenu">
      <li @click="refreshSelectedTag(selectedTag)"><i class="el-icon-refresh-right"></i> 刷新页面</li>
      <li v-if="!isAffix(selectedTag)" @click="closeSelectedTag(selectedTag)"><i class="el-icon-close"></i> 关闭当前</li>
      <li @click="closeOthersTags"><i class="el-icon-circle-close"></i> 关闭其他</li>
      <li v-if="!isFirstView()" @click="closeLeftTags"><i class="el-icon-back"></i> 关闭左侧</li>
      <li v-if="!isLastView()" @click="closeRightTags"><i class="el-icon-right"></i> 关闭右侧</li>
      <li @click="closeAllTags(selectedTag)"><i class="el-icon-circle-close"></i> 全部关闭</li>
    </ul>
  </div>
</template>

<script>
  import ScrollPane from './ScrollPane'
  import path from 'path'

  export default {
    components: { ScrollPane },
    data() {
      return {
        // 右键菜单隐藏对应布尔值
        visible: false,
        //右键菜单对应位置
        top: 0,
        left: 0,
        // 选择的标签
        selectedTag: {},
        // 固钉标签，不可删除
        affixTags: []
      }
    },
    // 计算属性
    computed: {
      visitedViews() {
        return this.$store.state.tagsView.visitedViews
      },
      routes() {
        return this.$store.state.permission.routes
      },
    },
    // 监听
    watch: {
      // 监听路由变化
      $route() {
        this.addTags()
        this.moveToCurrentTag()
      },
      //监听右键菜单的值是否为true，如果是就创建全局监听点击事件，触发closeMenu事件隐藏菜单，如果是false就删除监听
      visible(value) {
        if (value) {
          document.body.addEventListener('click', this.closeMenu)
        } else {
          document.body.removeEventListener('click', this.closeMenu)
        }
      }
    },
    // 页面渲染后初始化
    mounted() {
      this.initTags()
      this.addTags()
    },
    methods: {
      isActive(route) {
        return route.path === this.$route.path
      },
      activeStyle(tag) {
        if (!this.isActive(tag)) return {};
        return {
          "background-color": this.theme,
          "border-color": this.theme
        };
      },
      isAffix(tag) {
        return tag.meta && tag.meta.affix
      },
      isFirstView() {
        try {
          return this.selectedTag.fullPath === this.visitedViews[1].fullPath || this.selectedTag.fullPath === '/index'
        } catch (err) {
          return false
        }
      },
      isLastView() {
        try {
          return this.selectedTag.fullPath === this.visitedViews[this.visitedViews.length - 1].fullPath
        } catch (err) {
          return false
        }
      },
      filterAffixTags(routes, basePath = '/') {
        let tags = []
        routes.forEach(route => {
          if (route.meta && route.meta.affix) {
            const tagPath = path.resolve(basePath, route.path)
            tags.push({
              fullPath: tagPath,
              path: tagPath,
              name: route.name,
              meta: { ...route.meta }
            })
          }
          if (route.children) {
            const tempTags = this.filterAffixTags(route.children, route.path)
            if (tempTags.length >= 1) {
              tags = [...tags, ...tempTags]
            }
          }
        })
        return tags
      },
      initTags() {
        const affixTags = this.affixTags = this.filterAffixTags(this.routes)
        for (const tag of affixTags) {
          // Must have tag name
          if (tag.name) {
            this.$store.dispatch('tagsView/addVisitedView', tag)
          }
        }
      },
      /* 添加页签 */
      addTags() {
        const { name } = this.$route
        if (name) {
          this.$store.dispatch('tagsView/addView', this.$route)
        }
        return false
      },
      /* 移动到当前页签 */
      moveToCurrentTag() {
        const tags = this.$refs.tag
        this.$nextTick(() => {
          for (const tag of tags) {
            if (tag.to.path === this.$route.path) {
              this.$refs.scrollPane.moveToTarget(tag)
              // when query is different then update
              if (tag.to.fullPath !== this.$route.fullPath) {
                this.$store.dispatch('tagsView/updateVisitedView', this.$route)
              }
              break
            }
          }
        })
      },
      refreshSelectedTag(view) {
        this.$store.dispatch('tagsView/delCachedView', view).then(() => {
          const { fullPath } = view
          this.$nextTick(() => {
            this.$router.replace({
              path: '/redirect' + fullPath
            })
          })
        })
      },
      closeSelectedTag(view) {
        this.$store.dispatch('tagsView/delView', view).then(({ visitedViews }) => {
          if (this.isActive(view)) {
            this.toLastView(visitedViews, view)
          }
        })
      },
      closeRightTags() {
        this.$store.dispatch('tagsView/delRightTags', this.selectedTag).then(visitedViews => {
          if (!visitedViews.find(i => i.fullPath === this.$route.fullPath)) {
            this.toLastView(visitedViews)
          }
        })
      },
      closeLeftTags() {
        this.$store.dispatch('tagsView/delLeftTags', this.selectedTag).then(visitedViews => {
          if (!visitedViews.find(i => i.fullPath === this.$route.fullPath)) {
            this.toLastView(visitedViews)
          }
        })
      },
      closeOthersTags() {
        this.$router.push(this.selectedTag)
        this.$store.dispatch('tagsView/delOthersViews', this.selectedTag).then(() => {
          this.moveToCurrentTag()
        })
      },
      closeAllTags(view) {
        this.$store.dispatch('tagsView/delAllViews').then(({ visitedViews }) => {
          if (this.affixTags.some(tag => tag.path === this.$route.path)) {
            return
          }
          this.toLastView(visitedViews, view)
        })
      },
      toLastView(visitedViews, view) {
        const latestView = visitedViews.slice(-1)[0]
        if (latestView) {
          this.$router.push(latestView.fullPath)
        } else {
          // now the default is to redirect to the home page if there is no tags-view,
          // you can adjust it according to your needs.
          if (view.name === 'Dashboard') {
            // to reload home page
            this.$router.replace({ path: '/redirect' + view.fullPath })
          } else {
            this.$router.push('/')
          }
        }
      },
      openMenu(tag, e) {
        const menuMinWidth = 105
        const offsetLeft = this.$el.getBoundingClientRect().left // container margin left
        const offsetWidth = this.$el.offsetWidth // container width
        const maxLeft = offsetWidth - menuMinWidth // left boundary
        const left = e.clientX - offsetLeft + 15 // 15: margin right

        if (left > maxLeft) {
          this.left = maxLeft
        } else {
          this.left = left
        }

        this.top = e.clientY
        this.visible = true
        this.selectedTag = tag
      },
      closeMenu() {
        this.visible = false
      },
      handleScroll() {
        this.closeMenu()
      }
    }
  }
</script>

<style lang="scss" scoped>
  .tags-view-container {
    height: 34px;
    width: 100%;
    background: #fff;
    border-bottom: 1px solid #d8dce5;
    box-shadow: 0 1px 3px 0 rgba(0, 0, 0, .12), 0 0 3px 0 rgba(0, 0, 0, .04);
    .tags-view-wrapper {
      .tags-view-item {
        display: inline-block;
        position: relative;
        cursor: pointer;
        height: 26px;
        line-height: 26px;
        border: 1px solid #d8dce5;
        color: #495060;
        background: #fff;
        padding: 0 8px;
        font-size: 12px;
        margin-left: 5px;
        margin-top: 4px;
        &:first-of-type {
          margin-left: 15px;
        }
        &:last-of-type {
          margin-right: 15px;
        }
        &.active {
          background-color: #42b983;
          color: #fff;
          border-color: #42b983;
          &::before {
            content: '';
            background: #fff;
            display: inline-block;
            width: 8px;
            height: 8px;
            border-radius: 50%;
            position: relative;
            margin-right: 2px;
          }
        }
      }
    }
    .contextmenu {
      margin: 0;
      background: #fff;
      z-index: 3000;
      position: absolute;
      list-style-type: none;
      padding: 5px 0;
      border-radius: 4px;
      font-size: 12px;
      font-weight: 400;
      color: #333;
      box-shadow: 2px 2px 3px 0 rgba(0, 0, 0, .3);
      li {
        margin: 0;
        padding: 7px 16px;
        cursor: pointer;
        &:hover {
          background: #eee;
        }
      }
    }
  }
</style>

<style lang="scss">
  //reset element css of el-icon-close
  .tags-view-wrapper {
    .tags-view-item {
      .el-icon-close {
        width: 16px;
        height: 16px;
        vertical-align: 2px;
        border-radius: 50%;
        text-align: center;
        transition: all .3s cubic-bezier(.645, .045, .355, 1);
        transform-origin: 100% 50%;
        &:before {
          transform: scale(.6);
          display: inline-block;
          vertical-align: -3px;
        }
        &:hover {
          background-color: #b4bccc;
          color: #fff;
        }
      }
    }
  }
</style>

4. 新建 ScrollPane 组件

这个组件主要是控制路由标签长度超出时左右按钮的滚动功能。在 TabsView 目录下，新建 ScrollPane.vue 文件，代码如下（示例）：

<template>
  <el-scrollbar ref="scrollContainer" :vertical="false" class="scroll-container" @wheel.native.prevent="handleScroll">
    <slot />
  </el-scrollbar>
</template>

<script>
const tagAndTagSpacing = 4 // tagAndTagSpacing

export default {
  name: 'ScrollPane',
  data() {
    return {
      left: 0
    }
  },
  computed: {
    scrollWrapper() {
      return this.$refs.scrollContainer.$refs.wrap
    }
  },
  mounted() {
    this.scrollWrapper.addEventListener('scroll', this.emitScroll, true)
  },
  beforeDestroy() {
    this.scrollWrapper.removeEventListener('scroll', this.emitScroll)
  },
  methods: {
    handleScroll(e) {
      const eventDelta = e.wheelDelta || -e.deltaY * 40
      const $scrollWrapper = this.scrollWrapper
      $scrollWrapper.scrollLeft = $scrollWrapper.scrollLeft + eventDelta / 4
    },
    emitScroll() {
      this.$emit('scroll')
    },
    moveToTarget(currentTag) {
      const $container = this.$refs.scrollContainer.$el
      const $containerWidth = $container.offsetWidth
      const $scrollWrapper = this.scrollWrapper
      const tagList = this.$parent.$refs.tag

      let firstTag = null
      let lastTag = null

      // find first tag and last tag
      if (tagList.length > 0) {
        firstTag = tagList[0]
        lastTag = tagList[tagList.length - 1]
      }

      if (firstTag === currentTag) {
        $scrollWrapper.scrollLeft = 0
      } else if (lastTag === currentTag) {
        $scrollWrapper.scrollLeft = $scrollWrapper.scrollWidth - $containerWidth
      } else {
        // find preTag and nextTag
        const currentIndex = tagList.findIndex(item => item === currentTag)
        const prevTag = tagList[currentIndex - 1]
        const nextTag = tagList[currentIndex + 1]

        // the tag's offsetLeft after of nextTag
        const afterNextTagOffsetLeft = nextTag.$el.offsetLeft + nextTag.$el.offsetWidth + tagAndTagSpacing

        // the tag's offsetLeft before of prevTag
        const beforePrevTagOffsetLeft = prevTag.$el.offsetLeft - tagAndTagSpacing

        if (afterNextTagOffsetLeft > $scrollWrapper.scrollLeft + $containerWidth) {
          $scrollWrapper.scrollLeft = afterNextTagOffsetLeft - $containerWidth
        } else if (beforePrevTagOffsetLeft < $scrollWrapper.scrollLeft) {
          $scrollWrapper.scrollLeft = beforePrevTagOffsetLeft
        }
      }
    }
  }
}
</script>

<style lang="scss" scoped>
.scroll-container {
  white-space: nowrap;
  position: relative;
  overflow: hidden;
  width: 100%;
  ::v-deep {
    .el-scrollbar__bar {
      bottom: 0px;
    }
    .el-scrollbar__wrap {
      height: 49px;
    }
  }
}
</style>

5. 引入 tabsView 组件

修改 layout/components/index.js 文件，引入组件，代码如下（示例）：

export { default as TagsView } from './TagsView/index.vue'

修改 layout/index.vue 文件，使用 tabsView 组件，代码如下（示例）：

<template>
  <div :class="classObj" class="app-wrapper">
    <div v-if="device==='mobile'&&sidebar.opened" class="drawer-bg" @click="handleClickOutside" />
    <!-- 左侧侧边栏菜单 -->
    <sidebar class="sidebar-container" />
    <div class="main-container">
      <div :class="{'fixed-header':fixedHeader}">
        <navbar />
        <!--多页签导航栏-->
        <tags-view v-if="needTagsView" />
      </div>
      <app-main />
    </div>
  </div>
</template>

<script>
import { Navbar, Sidebar, AppMain, TagsView } from './components'
import ResizeMixin from './mixin/ResizeHandler'

export default {
  name: 'Layout',
  components: {
    Navbar,
    Sidebar,
    AppMain,
    TagsView
  },
  mixins: [ResizeMixin],
  computed: {
    needTagsView() {
      return true
    },
    ...
  },
  methods: {
    handleClickOutside() {
      this.$store.dispatch('app/closeSideBar', { withoutAnimation: false })
    }
  }
}
</script>

6. 使用 keep-alive 组件，进行页签的缓存

修改 layout/components/AppMain.vue 文件，使用 keep-alive 组件，进行页签的缓存，代码如下（示例）：

<template>
  <section class="app-main">
    <transition name="fade-transform" mode="out-in">
      <keep-alive :include="cachedViews">
        <router-view :key="key" />
      </keep-alive>
    </transition>
  </section>
</template>

<script>
export default {
  name: 'AppMain',
  computed: {
    cachedViews() {
      return this.$store.state.tagsView.cachedViews
    },
    key() {
      return this.$route.path
    }
  }
}
</script>

<style scoped>
.app-main {
  /*50 = navbar  */
  min-height: calc(100vh - 50px);
  width: 100%;
  position: relative;
  overflow: hidden;
}
.fixed-header+.app-main {
  padding-top: 50px;
}
</style>

<style lang="scss">
// fix css style bug in open el-dialog
.el-popup-parent--hidden {
  .fixed-header {
    padding-right: 15px;
  }
}
</style>