【Vue3】keep-alive 缓存组件
当在 Vue.js 中使用
v-if 选择某个确定的组件进行渲染。也可以使用 或其他组件标签将它们包裹起来，再通过 v-if 选择确定的某个组件进行渲染。因此 keep-alive 标签里面有且只有一个子节点（或者说只能渲染一个子节点）。这些子组件可以通过动态组件或者其他方式进行切换。
当一个被
1. keep-alive 和 v-show 的区别
- 作用：
v-show：用于根据条件动态显示或隐藏组件。它通过控制 display CSS 属性来决定组件是否在 DOM 中渲染。
- 使用场景：
v-show：适用于根据某些条件动态显示或隐藏单个组件。例如，根据用户权限动态显示不同的导航菜单。
- 对组件实例的影响：
v-show：每次切换显示或隐藏时，组件实例会保持不变，存在于真实 DOM ，并且会触发相应的生命周期钩子函数 beforeUpdate 和 updated。
2. keep-alive 使用案例
App.vue
<template>
<el-button type="primary" @click="flag = !flag"> 切换组件el-button>
<keep-alive :exclude="['A']">
<AVue v-if="flag">AVue>
<B v-else>B>
keep-alive>
template>
<script setup lang="ts">
import { ref } from 'vue';
import AVue from './components/A.vue'
import B from './components/B.vue'
const flag = ref<boolean>(true)
script>
<style scoped>style>
A.vue
<template>
<h1 style="margin: 10px;">我是A组件h1>
<el-form :model="form" label-width="120px">
<el-form-item label="Activity name">
<el-input v-model="form.name" />
el-form-item>
<el-form-item label="Activity zone">
<el-select v-model="form.region" placeholder="please select your zone">
<el-option label="Zone one" value="shanghai" />
<el-option label="Zone two" value="beijing" />
el-select>
el-form-item>
<el-form-item label="Activity time">
<el-col :span="11">
<el-date-picker v-model="form.date1" type="date" placeholder="Pick a date" style="width: 100%" />
el-col>
<el-col :span="2" class="text-center">
<span class="text-gray-500">-span>
el-col>
<el-col :span="11">
<el-time-picker v-model="form.date2" placeholder="Pick a time" style="width: 100%" />
el-col>
el-form-item>
<el-form-item label="Instant delivery">
<el-switch v-model="form.delivery" />
el-form-item>
<el-form-item label="Activity type">
<el-checkbox-group v-model="form.type">
<el-checkbox label="Online activities" name="type" />
<el-checkbox label="Promotion activities" name="type" />
<el-checkbox label="Offline activities" name="type" />
<el-checkbox label="Simple brand exposure" name="type" />
el-checkbox-group>
el-form-item>
<el-form-item label="Resources">
<el-radio-group v-model="form.resource">
<el-radio label="Sponsor" />
<el-radio label="Venue" />
el-radio-group>
el-form-item>
<el-form-item label="Activity form">
<el-input v-model="form.desc" type="textarea" />
el-form-item>
<el-form-item>
<el-button type="primary" @click="onSubmit">Createel-button>
<el-button>Cancelel-button>
el-form-item>
el-form>
template>
<script lang="ts" setup>
import { reactive } from 'vue'
// do not use same name with ref
const form = reactive({
name: '',
region: '',
date1: '',
date2: '',
delivery: false,
type: [],
resource: '',
desc: '',
})
const onSubmit = () => {
console.log('submit!')
}
script>
B.vue
<template>
<h1 style="margin: 10px;">我是B组件h1>
<el-form ref="ruleFormRef" :model="ruleForm" :rules="rules" label-width="120px" class="demo-ruleForm" :size="formSize"
status-icon>
<el-form-item label="Activity name" prop="name">
<el-input v-model="ruleForm.name" />
el-form-item>
<el-form-item label="Activity zone" prop="region">
<el-select v-model="ruleForm.region" placeholder="Activity zone">
<el-option label="Zone one" value="shanghai" />
<el-option label="Zone two" value="beijing" />
el-select>
el-form-item>
<el-form-item label="Activity count" prop="count">
<el-select-v2 v-model="ruleForm.count" placeholder="Activity count" :options="options" />
el-form-item>
<el-form-item label="Activity time" required>
<el-col :span="11">
<el-form-item prop="date1">
<el-date-picker v-model="ruleForm.date1" type="date" label="Pick a date" placeholder="Pick a date"
style="width: 100%" />
el-form-item>
el-col>
<el-col class="text-center" :span="2">
<span class="text-gray-500">-span>
el-col>
<el-col :span="11">
<el-form-item prop="date2">
<el-time-picker v-model="ruleForm.date2" label="Pick a time" placeholder="Pick a time" style="width: 100%" />
el-form-item>
el-col>
el-form-item>
<el-form-item label="Instant delivery" prop="delivery">
<el-switch v-model="ruleForm.delivery" />
el-form-item>
<el-form-item label="Activity type" prop="type">
<el-checkbox-group v-model="ruleForm.type">
<el-checkbox label="Online activities" name="type" />
<el-checkbox label="Promotion activities" name="type" />
<el-checkbox label="Offline activities" name="type" />
<el-checkbox label="Simple brand exposure" name="type" />
el-checkbox-group>
el-form-item>
<el-form-item label="Resources" prop="resource">
<el-radio-group v-model="ruleForm.resource">
<el-radio label="Sponsorship" />
<el-radio label="Venue" />
el-radio-group>
el-form-item>
<el-form-item label="Activity form" prop="desc">
<el-input v-model="ruleForm.desc" type="textarea" />
el-form-item>
<el-form-item>
<el-button type="primary" @click="submitForm(ruleFormRef)">
Create
el-button>
<el-button @click="resetForm(ruleFormRef)">Resetel-button>
el-form-item>
el-form>
template>
<script lang="ts" setup>
import { reactive, ref } from 'vue'
import type { FormInstance, FormRules } from 'element-plus'
interface RuleForm {
name: string
region: string
count: string
date1: string
date2: string
delivery: boolean
type: string[]
resource: string
desc: string
}
const formSize = ref('default')
const ruleFormRef = ref<FormInstance>()
const ruleForm = reactive<RuleForm>({
name: '',
region: '',
count: '',
date1: '',
date2: '',
delivery: false,
type: [],
resource: '',
desc: '',
})
const rules = reactive<FormRules<RuleForm>>({
name: [
{ required: true, message: 'Please input Activity name', trigger: 'blur' },
{ min: 3, max: 5, message: 'Length should be 3 to 5', trigger: 'blur' },
],
region: [
{
required: true,
message: 'Please select Activity zone',
trigger: 'change',
},
],
count: [
{
required: true,
message: 'Please select Activity count',
trigger: 'change',
},
],
date1: [
{
type: 'date',
required: true,
message: 'Please pick a date',
trigger: 'change',
},
],
date2: [
{
type: 'date',
required: true,
message: 'Please pick a time',
trigger: 'change',
},
],
type: [
{
type: 'array',
required: true,
message: 'Please select at least one activity type',
trigger: 'change',
},
],
resource: [
{
required: true,
message: 'Please select activity resource',
trigger: 'change',
},
],
desc: [
{ required: true, message: 'Please input activity form', trigger: 'blur' },
],
})
const submitForm = async (formEl: FormInstance | undefined) => {
if (!formEl) return
await formEl.validate((valid, fields) => {
if (valid) {
console.log('submit!')
} else {
console.log('error submit!', fields)
}
})
}
const resetForm = (formEl: FormInstance | undefined) => {
if (!formEl) return
formEl.resetFields()
}
const options = Array.from({ length: 10000 }).map((_, idx) => ({
value: `${idx + 1}`,
label: `${idx + 1}`,
}))
script>
3. 因注释导致的意外错误
写入注释：
报错：
因此 keep-alive 组件内不要使用注释，会被解析为子节点
解决方法：
-
keep-alive内部不写注释 -
使用
或其他组件标签将它们包裹起来- 此时 可以认为 利用了
keep-alive标签里面有且只有一个子节点（或者说只能渲染一个子节点）
- 此时 可以认为 利用了
<keep-alive :exclude="['A']">
<template v-if="flag">
<AVue>AVue>
template>
<template v-else>
<B>B>
template>
keep-alive>
4. keep-alive 生命周期
-
activated：被缓存的组件激活时调用。
-
deactivated：被缓存的组件停用时调用。
App.vue
<template>
<el-button type="primary" @click="flag = !flag"> 切换组件el-button>
<keep-alive :exclude="['B']">
<AVue v-if="flag">AVue>
<B v-else>B>
keep-alive>
template>
<script setup lang="ts">
import { ref } from 'vue';
import AVue from './components/A.vue'
import B from './components/B.vue'
const flag = ref<boolean>(true)
script>
<style scoped>style>
A.vue
<template>
<h1 style="margin: 10px;">我是A组件h1>
<el-form :model="form" label-width="120px">
<el-form-item label="Activity name">
<el-input v-model="form.name" />
el-form-item>
<el-form-item label="Activity zone">
<el-select v-model="form.region" placeholder="please select your zone">
<el-option label="Zone one" value="shanghai" />
<el-option label="Zone two" value="beijing" />
el-select>
el-form-item>
<el-form-item label="Activity time">
<el-col :span="11">
<el-date-picker v-model="form.date1" type="date" placeholder="Pick a date" style="width: 100%" />
el-col>
<el-col :span="2" class="text-center">
<span class="text-gray-500">-span>
el-col>
<el-col :span="11">
<el-time-picker v-model="form.date2" placeholder="Pick a time" style="width: 100%" />
el-col>
el-form-item>
<el-form-item label="Instant delivery">
<el-switch v-model="form.delivery" />
el-form-item>
<el-form-item label="Activity type">
<el-checkbox-group v-model="form.type">
<el-checkbox label="Online activities" name="type" />
<el-checkbox label="Promotion activities" name="type" />
<el-checkbox label="Offline activities" name="type" />
<el-checkbox label="Simple brand exposure" name="type" />
el-checkbox-group>
el-form-item>
<el-form-item label="Resources">
<el-radio-group v-model="form.resource">
<el-radio label="Sponsor" />
<el-radio label="Venue" />
el-radio-group>
el-form-item>
<el-form-item label="Activity form">
<el-input v-model="form.desc" type="textarea" />
el-form-item>
<el-form-item>
<el-button type="primary" @click="onSubmit">Createel-button>
<el-button>Cancelel-button>
el-form-item>
el-form>
template>
<script lang="ts" setup>
import { reactive,onMounted,onUnmounted,onDeactivated,onActivated } from 'vue'
// do not use same name with ref
const form = reactive({
name: '',
region: '',
date1: '',
date2: '',
delivery: false,
type: [],
resource: '',
desc: '',
})
const onSubmit = () => {
console.log('submit!')
}
onMounted(() => {
console.log('初始化')
}),
onActivated(() => {
console.log('keep-alive初始化')
})
onDeactivated(() => {
console.log('keep-alive销毁')
})
onUnmounted(() => {
console.log('销毁')
})
script>
B.vue
<template>
<h1 style="margin: 10px;">我是B组件h1>
<el-form ref="ruleFormRef" :model="ruleForm" :rules="rules" label-width="120px" class="demo-ruleForm" :size="formSize"
status-icon>
<el-form-item label="Activity name" prop="name">
<el-input v-model="ruleForm.name" />
el-form-item>
<el-form-item label="Activity zone" prop="region">
<el-select v-model="ruleForm.region" placeholder="Activity zone">
<el-option label="Zone one" value="shanghai" />
<el-option label="Zone two" value="beijing" />
el-select>
el-form-item>
<el-form-item label="Activity count" prop="count">
<el-select-v2 v-model="ruleForm.count" placeholder="Activity count" :options="options" />
el-form-item>
<el-form-item label="Activity time" required>
<el-col :span="11">
<el-form-item prop="date1">
<el-date-picker v-model="ruleForm.date1" type="date" label="Pick a date" placeholder="Pick a date"
style="width: 100%" />
el-form-item>
el-col>
<el-col class="text-center" :span="2">
<span class="text-gray-500">-span>
el-col>
<el-col :span="11">
<el-form-item prop="date2">
<el-time-picker v-model="ruleForm.date2" label="Pick a time" placeholder="Pick a time" style="width: 100%" />
el-form-item>
el-col>
el-form-item>
<el-form-item label="Instant delivery" prop="delivery">
<el-switch v-model="ruleForm.delivery" />
el-form-item>
<el-form-item label="Activity type" prop="type">
<el-checkbox-group v-model="ruleForm.type">
<el-checkbox label="Online activities" name="type" />
<el-checkbox label="Promotion activities" name="type" />
<el-checkbox label="Offline activities" name="type" />
<el-checkbox label="Simple brand exposure" name="type" />
el-checkbox-group>
el-form-item>
<el-form-item label="Resources" prop="resource">
<el-radio-group v-model="ruleForm.resource">
<el-radio label="Sponsorship" />
<el-radio label="Venue" />
el-radio-group>
el-form-item>
<el-form-item label="Activity form" prop="desc">
<el-input v-model="ruleForm.desc" type="textarea" />
el-form-item>
<el-form-item>
<el-button type="primary" @click="submitForm(ruleFormRef)">
Create
el-button>
<el-button @click="resetForm(ruleFormRef)">Resetel-button>
el-form-item>
el-form>
template>
<script lang="ts" setup>
import { reactive, ref } from 'vue'
import type { FormInstance, FormRules } from 'element-plus'
interface RuleForm {
name: string
region: string
count: string
date1: string
date2: string
delivery: boolean
type: string[]
resource: string
desc: string
}
const formSize = ref('default')
const ruleFormRef = ref<FormInstance>()
const ruleForm = reactive<RuleForm>({
name: '',
region: '',
count: '',
date1: '',
date2: '',
delivery: false,
type: [],
resource: '',
desc: '',
})
const rules = reactive<FormRules<RuleForm>>({
name: [
{ required: true, message: 'Please input Activity name', trigger: 'blur' },
{ min: 3, max: 5, message: 'Length should be 3 to 5', trigger: 'blur' },
],
region: [
{
required: true,
message: 'Please select Activity zone',
trigger: 'change',
},
],
count: [
{
required: true,
message: 'Please select Activity count',
trigger: 'change',
},
],
date1: [
{
type: 'date',
required: true,
message: 'Please pick a date',
trigger: 'change',
},
],
date2: [
{
type: 'date',
required: true,
message: 'Please pick a time',
trigger: 'change',
},
],
type: [
{
type: 'array',
required: true,
message: 'Please select at least one activity type',
trigger: 'change',
},
],
resource: [
{
required: true,
message: 'Please select activity resource',
trigger: 'change',
},
],
desc: [
{ required: true, message: 'Please input activity form', trigger: 'blur' },
],
})
const submitForm = async (formEl: FormInstance | undefined) => {
if (!formEl) return
await formEl.validate((valid, fields) => {
if (valid) {
console.log('submit!')
} else {
console.log('error submit!', fields)
}
})
}
const resetForm = (formEl: FormInstance | undefined) => {
if (!formEl) return
formEl.resetFields()
}
const options = Array.from({ length: 10000 }).map((_, idx) => ({
value: `${idx + 1}`,
label: `${idx + 1}`,
}))
script>
