Vue + vuex fallback to initial position

Li gulare 2020-11-12 23:46:32
vue vuex fallback initial position


Let's draw two pictures first ( you 're right , You are still 9012, As a senior designer, my only skill is to leave blank ), Explain the problem briefly
No fallback positioning ( Back off from landing page , Go back to... Every time A Location ) I want to die , Every time you need to manually relocate to select , Your big brother wants to kill you when he sees you do this :

After adding fallback positioning ( Back off from landing page , Navigate to where you click ) Ha , Good use of explosion Is there any ~:


according to WBD International common practice ( I made it up ), First of all demo Make an index of the files used in , It is convenient to have a macro perspective on the whole fallback function , It's easier to understand how the whole process works , Do have skill in mind .
This fallback positioning demo It's all about 5 File , They are as follows :
BackToA.vue   Components A, That is to say, the components that need to be back positioned , That's the scene of the first traffic accident
Alphabet.vue   Components B, Jump to landing page , Is not important
index.js   In this file , Configure the routing , add to meta attribute (keepAlive), Very important
App.vue Template file , Import components (router-view), Depending on whether the route adds meta Property to determine whether to enable keep-alive Cache components
main.js Entrance file , introduce vuex, stay state Definition _scrollTop To record scrollTop value , And change state It's worth it actions Method to submit mutation Update status
demo The directory structure is shown in the figure below :

See this , Do you feel very macro . Is there any art in your heart , To this little demo There was contempt for the king . Young man, please stay , Words , No way with skill , Stop at surgery , Give me another two minutes , Let me freeze my memory , say “ Avenue ”.
Avenue : First of all, for components BackToA Enable keep-alive cache , When components BackToA Record the... Of the current page when scrolling up and down scrollTop value , And store this value in vuex Of state in . When from landing components B Back to components BackToA when , Caching works , Components BackToA No more re rendering . Now get vuex state Stored in the scrollTop value , Assign a value to BackToA Components , Realize positioning to the position before jump .
In fact, I am a programmer ,ok, Let's start our favorite programming session .
1. introduce vuex Storage scrollTop value
because vuex Is the core of the whole process , First, put this part in the first one to sort out and facilitate the subsequent process to continue ( We've all suffered the pain of being interrupted. I'm not allowed to )( The interruptions are all work , Don't associate with anything else ).
Open the entry file main.js( It's usually this document ), Define a... In this file store Constant 、 Store a _scrollTop To store the scrollTop value 、 introduce vuex, And enable the
Source code is as follows

import Vuex from 'vuex'
Vue.use(Vuex)
const store = new Vuex.Store({
  state: {
    _scrollTop: 0  // Storage components scrollTop value
  },
  mutations: {
    updatePosition (state, payload) {
      state._scrollTop = payload.top  // change scrollTop value
    }
  },
  actions: {
    updatePosition ({commit}, top) { 
      commit({type: 'updatePosition', top: top}) // Submit mutation Change state
    }
  }
})

2. Create components BackToA
① introduce vuex Medium mapState and mapActions

import { mapState, mapActions } from 'vuex'

② stay computed The calculation attribute defines demoTop Variable , And read state Medium _scrollTop Value to assign

computed: {
    ...mapState({
      demoTop: state => state._scrollTop,  // obtain state Stored in the top value
    }),
},


③ Create monitor page scrolling method , Monitor the current page in real time scrollTop value , This monitor is on mounted The trigger in the hook is : Now the page dom Finished rendering

  mounted: function () {
    console.log("==mounted===");
    document.querySelector('.hello').addEventListener('scroll', this.handleScroll, false);
  },
  methods:{
    handleScroll(){
      this.box = document.querySelector('.hello')
    },       
  },


④ Get the current page in real time scrollTop value , Submit mutation Update status

  methods:{
    handleScroll(){
      this.box = document.querySelector('.hello')
      this.updatePosition(this.box.scrollTop)
    },   
    ...mapActions([
      'updatePosition'
    ]),       
  },


⑤ Cache data read , to update scrollTop value , Achieve positioning

  activated () {
    document.querySelector('.hello').scrollTop = this.demoTop // Update the scrollTop value
  },


⑥ The page layout
notes : What we get in this example is scrollTop value , It belongs to class='hello' Of , So in components BackToA There must be only class='hello' Of div Support overflow:scroll Talent

<template>
  <div class="hello">
    <ul>
      <li v-for="(item,index) in 26" :key="index">
        <router-link :to="{ name: 'Alphabet', params: { letter: String.fromCharCode(64+item) }}">{
{String.fromCharCode(64+item)}}</router-link>        
        </li>  
    </ul>
  </div>
</template>
<style scoped>
.hello{
  height:600px;
  overflow:scroll;
}
.hello>ul{
  height:auto;
  overflow:hidden;
  background:#eee;
}
.hello>ul>li{
  height:60px;
  line-height:60px;
  width:100%;
  float:left;
  margin:0;
  border-bottom:1px dashed #ccc;
}
</style>


3. Create landing components Alphabet

<template>
  <div class="hello">
    <div><button @click="goback">goback</button></div>
    <ul>
      <li>
        this is <strong>{
{ $route.params.letter }}</strong>
      </li>      
    </ul>
  </div>
</template>

4. Configure component cache
① stay router/index.js In the document /backto/backtoa Route add meta Cache properties :meta: { keepAlive: true }

   {
      path: '/backto/backtoa',
      name: 'BackToA',
      component: BackToA,
      meta: { keepAlive: true }
    }    


② stay App.vue Template file according to whether to add meta Property to determine whether the caching mechanism is enabled :

<template>
  <div id="app">
    <keep-alive>
      <router-view v-if="$route.meta.keepAlive"></router-view>
    </keep-alive>
    <router-view v-if="!$route.meta.keepAlive"></router-view>
  </div>
</template>


** See you later **


 

版权声明
本文为[Li gulare]所创,转载请带上原文链接,感谢

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