VUE 笔记 ilovecoding 179 Home离开时记录状态和位置

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在Home页面滚动后，切换到其它页面再回来，数据又回到了顶部，体验不好

1. App.vue 中使用 keep-alive

• Vue3的使用方式
  • https://router.vuejs.org/zh/guide/migration/index.html#router-view-、-keep-alive-和-transition
  • https://github.com/vuejs/rfcs/blob/master/active-rfcs/0034-router-view-keep-alive-transitions.md

<template>
  <router-view v-slot="{ Component }">
    <keep-alive>
      <component :is="Component"/>
    </keep-alive>
  </router-view>
  <main-tab-bar/>
</template>

<script>
import MainTabBar from 'components/content/mainTabBar/MainTabBar'

export default {
  name: 'App',
  components: {
    MainTabBar
  }
}
</script>

<style>
@import './assets/css/base.css';
</style>

注：使用新版本的better-scroll，到这儿就行了，以下调整是解决旧版本的问题

2. Scroll.vue 中增加方法 getScrollY（非必要，主要是体现封装）

<template>
  <div class="wrapper" ref="wrapper">
    <div class="content">
      <slot></slot>
    </div>
  </div>
</template>

<script>
  import BScroll from '@better-scroll/core'
  import PullUp from '@better-scroll/pull-up'
  import ObserveImage from '@better-scroll/observe-image'

  import {debounce} from 'common/utils'

  export default {
    name: 'Scroll',
    props: {
      probeType: {
        type: Number,
        default: 0
      },
      pullUpLoad: {
        type: Boolean,
        default: false
      },
      observeImage: {
        type: Boolean,
        default: false
      }
    },
    data() {
      return {
        scroll: null
      }
    },
    methods: {
      createScroll() {
        BScroll.use(PullUp)
        BScroll.use(ObserveImage)
        // 创建BScroll对象
        this.scroll = new BScroll(this.$refs.wrapper, {
          click: true,
          probeType: this.probeType,
          pullUpLoad: this.pullUpLoad,
          observeImage: this.observeImage
        })

        if (this.probeType === 2 || this.probeType === 3) {
          // 监听滚动位置
          this.scroll.on('scroll', (position) => {
            this.$emit('scroll', position)
          })
        }

        if (this.pullUpLoad) {
          // 监听上拉事件
          this.scroll.on('pullingUp', () => {
            this.$emit('pullingUp')
          })
        }

        const refresh = debounce(this.refresh, 200)
        // 监听item图片加载完成
        this.$EventBus.on('itemImageLoad', () => {
          refresh()
        })
      },
      scrollTo(x, y, time = 300) {
        this.scroll.scrollTo(x, y, time)
      },
      finishPullUp() {
        this.scroll.finishPullUp()
      },
      refresh() {
        console.log('-------------------')
        this.scroll.refresh();
      },
      getScrollY() {
        return this.scroll.y
      }
    },
    mounted() {
      this.createScroll()
    }
  }
</script>

<style scoped></style>

3. Home.vue中用 saveY 记录位置

<template>
  <div id="home">

    <nav-bar class="home-nav">
      <template v-slot:center>
        <div>购物街</div>
      </template>
    </nav-bar>

    <tab-control ref="tabControl1" :titles="['流行', '新款', '精选']" @tabClick="tabClick" class="tab-control" v-show="isTabFixed"/>

    <scroll 
      class="content" 
      ref="scroll" 
      :probe-type="3" 
      @scroll="contentScroll" 
      :pull-up-load="true"
      @pullingUp="loadMore"
      :observe-image="false">
      <home-swiper :banners="banners" @swiperImageLoad="swiperImageLoad"/>
      <recommend-view :recommends="recommends"/>
      <feature-view />
      <tab-control ref="tabControl2" :titles="['流行', '新款', '精选']" @tabClick="tabClick"/>
      <goods-list :goods="showGoods"/>
    </scroll>

    <back-top @click="backClick" v-show="isShowBackTop"/>
  </div>
</template>

<script>

import HomeSwiper from './childComps/HomeSwiper'
import RecommendView from './childComps/RecommendView'
import FeatureView from './childComps/FeatureView'

import NavBar from 'components/common/navbar/NavBar'
import TabControl from 'components/content/tabControl/TabControl'
import GoodsList from 'components/content/goods/GoodsList'
import Scroll from 'components/common/scroll/Scroll'
import BackTop from 'components/content/backTop/BackTop'

import { getHomeMultiData, getHomeGoods } from 'network/home'

export default {
  name: 'Home',
  components: {
    HomeSwiper,
    RecommendView,
    FeatureView,
    NavBar,
    TabControl,
    GoodsList,
    Scroll,
    BackTop
  },
  data() {
    return {
      banners: [],
      recommends: [],
      goods: {
        'pop': {page: 0, list: []},
        'new': {page: 0, list: []},
        'sell': {page: 0, list: []}
      },
      currentType: 'pop',
      isShowBackTop: false,
      tabOffsetTop: 0,
      isTabFixed: false,
      saveY: 0
    }
  },
  computed: {
    showGoods() {
      return this.goods[this.currentType].list
    }
  },
  methods: {
    /**
     * 事件监听相关的方法
     */
    tabClick(index) {
      switch (index) {
        case 0:
          this.currentType = 'pop'
          break
        case 1:
          this.currentType = 'new'
          break
        case 2:
          this.currentType = 'sell'
          break
      }
      this.$refs.tabControl1.currentIndex = index
      this.$refs.tabControl2.currentIndex = index
    },
    backClick() {
      this.$refs.scroll.scrollTo(0, 0)
    },
    contentScroll(position) {
      // 1. 判断backTop是否显示
      this.isShowBackTop = position.y < -1000
      // 2. 决定tablControl是否吸顶（position：fixed）
      this.isTabFixed = (-position.y) > this.tabOffsetTop
    },
    loadMore() {
      this.getHomeGoods(this.currentType).then(() => {
        this.$refs.scroll.finishPullUp()
      })
    },
    swiperImageLoad() {
      // 获取tabControl的offsetTop
      // 所有的组件都有一个属性$el，用户获取组件中的元素
      this.tabOffsetTop = this.$refs.tabControl2.$el.offsetTop
    },
    /**
     * 网络请求相关的方法
     */
    getHomeMultiData() {
      getHomeMultiData().then(res => {
        this.banners = res.data.banner.list
        this.recommends = res.data.recommend.list
      })
    },
    getHomeGoods(type) {
      const page = this.goods[type].page + 1
      return getHomeGoods(type, page).then(res => {
        this.goods[type].list.push(...res.data.list)
        this.goods[type].page++
      })
    }
  },
  created() {
    // 1. 请求多个数据
    this.getHomeMultiData()
    // 2. 请求商品数据
    this.getHomeGoods('pop')
    this.getHomeGoods('new')
    this.getHomeGoods('sell')
  },
  mounted() {
    
  },
  unmounted() {
    console.log('Home unmounted')
  },
  activated() {
    this.$refs.scroll.scrollTo(0, this.saveY, 0)
    this.$refs.scroll.refresh()
  },
  deactivated() {
    this.saveY = this.$refs.scroll.getScrollY()
  }
}
</script>

<style scoped>
  #home {
    /* padding-top: 44px; */
    height: 100vh;
    position: relative;
  }

  .home-nav {
    background-color: var(--color-tint);
    color: #fff;

    /* 在使用浏览器原生滚动时，为了让导航不跟随一起滚动*/
    /* position: fixed;
    left: 0;
    right: 0;
    top: 0;
    z-index: 9; */
  }

  .content {
    overflow: hidden;
    position: absolute;
    top: 44px;
    bottom: 49px;
    left: 0;
    right: 0;
  }

  .tab-control {
    position: relative;
    z-index: 9;
  }

  /** 如果要换成这种，需要去掉上面home的 padding-top: 44px; */
  /* .content {
    height: calc(100% - 93px);
    overflow: hidden;
    margin-top: 44px;
  } */
</style>