【Vue3基础】组件保持存活、异步加载组件

一、组件保持存活

1、需求描述

点击按钮跳转到其他组件后，原组件不会被销毁

2、知识整理

1）组件生命周期

创建期：beforeCreate、created

挂载期：beforeMount、mounted

更新期：beforeUpdate、updated

销毁期：beforeUnmount、unmounted

2)保持组件存活keep-alive

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 <keep-alive>
    <component :is="tabComponent"></component>
  </keep-alive>

3）实现异步组件加载

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defineAsyncComponent

3、代码演示

1）文件

2）App.vue文件

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<template>
  <keep-alive>
    <component :is="tabComponent"></component>
  </keep-alive>
  <button @click="changeHandle">切换按钮</button>
</template>
<script>
import ComponentA from "./components/ComponentA.vue";
import ComponentB from "./components/ComponentB.vue";
export default{
  data(){
    return{
      tabComponent:"ComponentA"
    }
  },
  components: { 
    ComponentA,
    ComponentB
  },
  methods:{
    changeHandle(){
      this.tabComponent=this.tabComponent=="ComponentA"?"ComponentB":"ComponentA"
    }
  }
}
</script>

3）ComponentA.vue文件

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<template>
    <h3>ComponentA</h3>
    <p>{{ message }}</p>
    <button @click="updateHandle">更新数据</button>
</template>
<script>
export default{
    data(){
        return {
            message:"老数据"
        }
    },
    beforeUnmount(){
        console.log("组件卸载之前");
    },
    unmounted(){
        console.log("组件卸载之后");
    },
    methods:{
        updateHandle(){
            this.message="新数据"
        }
    }
}
</script>

4）ComponentB.vue文件

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<template>
    <h3>ComponentB</h3>
</template>
<script>

</script>

5、效果展示

1）打开浏览器

2）点击"更新数据"按钮，"老数据"将变为"新数据"

3）点击"切换按钮"，跳转到组件B中

4）再点击"切换按钮"，跳转回组件A，仍保持显示"新数据"

>>>

二、异步加载组件

1、关键代码 App.vue文件

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<script>
import ComponentA from "./components/ComponentA.vue";
//import ComponentB from "./components/ComponentB.vue";
//异步加载B组件
import { defineAsyncComponent } from "vue";
const ComponentB=defineAsyncComponent(()=>import("./components/ComponentB.vue"))

2、效果展示

1）登录浏览器，B组件未被加载

2）点击切换按钮后，才加载B组件

三、学习链接

https://www.bilibili.com/video/BV1Rs4y127j8?p=37&spm_id_from=pageDriver&vd_source=841fee104972680a6cac4dbdbf144b50