Vue--keep-alive

IT利刃出鞘 2022-09-29 我要评论

简介

说明

本文用示例介绍Vue的keep-alive的用法。

keep-alive标签主要用于保留组件状态或避免重新渲染。

官网网址

https://v2.cn.vuejs.org/v2/api/#keep-alive

相关网址

vue2中的keep-alive使用总结及注意事项

公共代码

路由（router/index.js）

import Vue from 'vue'
import VueRouter from 'vue-router'
import Parent from '../components/Parent'
 
Vue.use(VueRouter)
 
const routes = [
  {
    path: '/',
    name: 'Parent',
    component: Parent
  }
 
]
 
const router = new VueRouter({
  routes
})
 
export default router

生命周期mixin（mixins/LifeCycle.js）

下边的两个页面组件都要打印生命周期，所以我把它抽出作为mixin。

export default {
  computed: {
    name () {
      return this.$options.name
    }
  },
  created () {
    console.log('created ==> ' + this.name)
  },
  activated () {
    console.log('activated ==> ' + this.name)
  },
  deactivated () {
    console.log('deactivated ==> ' + this.name)
  },
  destroyed () {
    console.log('destroyed ==> ' + this.name)
  }
}

子页面组件

components/CompA.vue

<template>
  <div class="outer">
    <div>
      这是CompA
    </div>
  </div>
</template>
 
<script>
import LifeCycle from '../mixins/LifeCycle'
 
export default {
  name: 'CompA',
  mixins: [LifeCycle]
}
</script>
 
<style scoped>
.outer {
  margin: 20px;
  border: 2px solid blue;
  padding: 20px;
}
</style>

components/CompB.vue

<template>
  <div class="outer">
    这是CompB
  </div>
</template>
 
<script>
import LifeCycle from '../mixins/LifeCycle'
 
export default {
  name: 'CompB',
  mixins: [LifeCycle]
}
</script>
 
<style scoped>
.outer {
  margin: 20px;
  border: 2px solid blue;
  padding: 20px;
}
</style>

动态组件实例

不加keep-alive

代码

components/Parent.vue

<template>
  <div class="outer">
    <div>
      这是Parent
    </div>
    <br>
    <button @click="useCompA">切换到CompA</button>
    |
    <button @click="useCompB">切换到CompB</button>
    <component :is="componentName"></component>
  </div>
</template>
 
<script>
import CompA from './CompA'
import CompB from './CompB'
 
export default {
  name: 'Parent',
  components: {
    CompA,
    CompB
  },
  data () {
    return {
      componentName: ''
    }
  },
  methods: {
    useCompA () {
      this.componentName = 'CompA'
    },
    useCompB () {
      this.componentName = 'CompB'
    }
  }
}
</script>
 
<style scoped>
.outer {
  margin: 20px;
  border: 2px solid red;
  padding: 20px;
}
</style>

测试

访问：http://localhost:8080/#/

可以发现：进入组件时调用created；离开组件时调用destroyed。

加keep-alive

代码

component/Parent.vue

将动态组件用keep-alive标签包起来。

<template>
  <div class="outer">
    <div>
      这是Parent
    </div>
    <br>
    <button @click="useCompA">切换到CompA</button>
    |
    <button @click="useCompB">切换到CompB</button>
    <keep-alive>
      <component :is="componentName"></component>
    </keep-alive>
  </div>
</template>
 
<script>
import CompA from './CompA'
import CompB from './CompB'
 
export default {
  name: 'Parent',
  components: {
    CompA,
    CompB
  },
  data () {
    return {
      componentName: ''
    }
  },
  methods: {
    useCompA () {
      this.componentName = 'CompA'
    },
    useCompB () {
      this.componentName = 'CompB'
    }
  }
}
</script>
 
<style scoped>
.outer {
  margin: 20px;
  border: 2px solid red;
  padding: 20px;
}
</style>

测试

访问：http://localhost:8080/#/

可以发现：进入组件时调用created、activated；离开组件时调用deactivated（不调用destroyed）。

router-view实例

不加keep-alive

代码

修改路由设置（router/index.js）

import Vue from 'vue'
import VueRouter from 'vue-router'
import Parent from '../components/Parent'
import CompA from '../components/CompA'
import CompB from '../components/CompB'
 
Vue.use(VueRouter)
 
const routes = [
  {
    path: '/',
    name: 'Parent',
    component: Parent
  },
  {
    path: '/compA',
    name: 'CompA',
    component: CompA
  },
  {
    path: '/compB',
    name: 'CompB',
    component: CompB
  }
]
 
const router = new VueRouter({
  routes
})
 
export default router

修改入口组件（components/Parent.vue）

<template>
  <div class="outer">
    <div>
      这是Parent
    </div>
    <br>
    <router-link :to="{name: 'CompA'}">跳转到CompA</router-link> 
    |
    <router-link :to="{name: 'CompB'}">跳转到CompB</router-link>
    <router-view></router-view>
  </div>
</template>
 
<script>
 
export default {
  name: 'Parent'
}
</script>
 
<style scoped>
.outer {
  margin: 20px;
  border: 2px solid red;
  padding: 20px;
}
</style>

测试

访问：http://localhost:8080/#/

可以发现：进入路由组件时调用created；离开路由组件时调用destroyed。

加keep-alive（加到App.vue里）

修改App.vue

将router-view标签包裹在keep-alive标签里。

<template>
  <div id="app">
    <div id="nav">
      <router-link to="/">Home</router-link>
      |
      <router-link to="/about">About</router-link>
    </div>
    <!-- 原来写法 -->
    <!-- <router-view/> -->
    <keep-alive>
      <router-view/>
    </keep-alive>
  </div>
</template>
 
<style>
<!-- 省略 -->
</style>

测试

访问：http://localhost:8080/#/

可以发现：进入组件时调用created、activated；离开组件时调用deactivated（不调用destroyed）。

加keep-alive（加到Parent.vue里）

说明

需要做如下两步：

Parent.vue：将router-view包裹在keep-alive里边
将CompA和CompB的路由作为Parent的嵌套路由（Children）

如果只修改Parent.vue，将router-view包裹在keep-alive里边，这样是没用的，跟没有加keep-alive效果一样。

代码

修改components/Parent.vue

<template>
  <div class="outer">
    <div>
      这是Parent
    </div>
    <br>
    <router-link :to="{name: 'CompA'}">跳转到CompA</router-link>
    |
    <router-link :to="{name: 'CompB'}">跳转到CompB</router-link>
    <keep-alive>
      <router-view></router-view>
    </keep-alive>
  </div>
</template>
 
<script>
 
export default {
  name: 'Parent'
}
</script>
 
<style scoped>
.outer {
  margin: 20px;
  border: 2px solid red;
  padding: 20px;
}
</style>

修改路由（router/index.js）

import Vue from 'vue'
import VueRouter from 'vue-router'
import Parent from '../components/Parent'
import CompA from '../components/CompA'
import CompB from '../components/CompB'
 
Vue.use(VueRouter)
 
const routes = [
  {
    path: '/',
    name: 'Parent',
    component: Parent,
    children: [
      {
        path: '/compA',
        name: 'CompA',
        component: CompA
      },
      {
        path: '/compB',
        name: 'CompB',
        component: CompB
      }
    ]
  }
 
]
 
const router = new VueRouter({
  routes
})
 
export default router

测试

访问：http://localhost:8080/#/