储存keep-alive内组件的滚动位置

Vue

keep-alive一般被用来缓存组件实例.当从一个组件切换到另一个时, 这个组件不会被销毁, 而会被保存起来供下次调用时使用.
遗憾的是, 如果被keep-alive包裹的组件中有滚动元素,keep-alive不会储存滚动位置.
需要在滚动时储存位置, 然后在组件被激活时还原.

keep-alive 组件有两个特殊的生命周期钩子: activated和deactivated.
activated在keep-alive组件激活时调用.
deactivated在keep-alive组件被停用时调用.
API — Vue.js

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{
 mounted() {
  // 获取组件根元素Dom
  const page = this.$el;
  // 绑定事件,滚动时,储存位置到this.scrollTop
  page.addEventListener("scroll", () => {
   this.scrollTop = page.scrollTop;
  });
 },
 // activated生命钩子在keep-alive被激活时调用
 activated() {
  // 如果曾滚动过,则还原位置
  if (this.scrollTop) {
   const page = this.$el;
   page.scrollTop = this.scrollTop;
  }
 },
 // deactivated生命钩子在keep-alive被停用时调用
 // 如果onScroll绑定在window之类的元素上,记得用removeEventListener删除事件
 deactivated() {}
};

另外,可以将这段代码储存为mixin, 需要时调用即可.

See the Pen [Vue] 记录keep-alive内组件的滚动位置 by aaronbird (@aaronbird) on CodePen. 

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<script src="https://cdnjs.cloudflare.com/ajax/libs/vue/2.6.9/vue.min.js">
<div class="app">
 <div class="main">
  <keep-alive>
   <!--    动态组件 -->
   <component :is="componentName">
  </keep-alive>
 </div>
 <!--   导航 -->
 <div class="navs">
  <div class="nav" @click="componentName = tag" v-for="tag of tags">
   {{tag}}
  </div>
 </div>
</div>
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body {
 margin: 0;
 font-size: 20px;
}

@mixin pin() {
 position: absolute;
 top: 0;
 left: 0;
 right: 0;
 bottom: 0;
 overflow: auto;
}

.app {
 height: 100vh;
 display: flex;
 flex-direction: column;
 .main {
  position: relative;
  flex: 1 1 auto;
  overflow: hidden;
  text-align: center;
  .home {
   color: red;
   background: blue; 
   @include pin();
  }
  .shop {
    color: blue;
    background: red;   
   @include pin();
  }
 }
 .navs {
  display: flex;
  flex: 0 0 50px;
  background: #ffa;
  align-items: center;
  .nav {
   flex: 1 1 auto;
   height: 100%;
   line-height: 50px;
   text-align: center;
   border-right: 1px solid rgba(0, 0, 0, 0.2);
   &:last-child {
    border-right: none;
   }
  }
 }
}
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// 定义mixin, 用于记录scroll位置
const keepScrollTop = {
 mounted() {
  // 获取组件根元素Dom
  const page = this.$el;
  // 绑定事件,滚动时,储存位置到this.scrollTop
  page.addEventListener("scroll", () => {
   this.scrollTop = page.scrollTop;
  });
 },
 // activated生命钩子在keep-alive被激活时调用
 activated() {
  // 如果曾滚动过,则还原位置
  if (this.scrollTop) {
   const page = this.$el;
   page.scrollTop = this.scrollTop;
  }
 },
 // deactivated生命钩子在keep-alive被停用时调用
 // 如果onScroll绑定在window之类的元素上,记得用removeEventListener删除事件
 deactivated() {}
};
// 定义组件home
Vue.component("home", {
 mixins: [keepScrollTop],
 template: `
  <div class="home">
    <div v-for="i of 50">{{i}}</div>
  </div>
`
});
// 定义组件shop
Vue.component("shop", {
 mixins: [keepScrollTop],
 template: `
  <div class="shop">
    <div v-for="i of 50">{{i}}</div>
  </div>
`
});
// 创建Vue实例
const app = new Vue({
 el: ".app",
 data: {
  tags: ["home", "shop"],
  componentName: "home"
 }
});