react引用其他组件Error: Element type is invalid: expected a string (for built-in components) or a class/fu

报错详情如下

Error: Element type is invalid: expected a string (for built-in
 components) or a class/function (for composite components) but
  got: undefined. You likely forgot to export your component from 
  the file it's defined in, or you might have mixed up default and 
  named imports.

先看下目录结构

home文件如下

import React from 'react'
import styles from './index.css'
import Announcement from './announcement.js'


class Home extends React.Component{
    constructor(props){
        super(props)
        this.state={}
    }
    render(){
        return(
            <div className={styles.bodys}>
                aaaa
                <div>
                    <Announcement/>
                </div>
            </div>
        );
    }
}

export default Home;

announcement文件主要如下

class Announcement extends React.Component{
    

    render() {
        return(
           <div>
               <Tops/>
               <Divider />
               <List/>
           </div>
        );
    }
}

然后他就报错

原因是我没有将 Announcement 抛出
在announcement 文件下加入

export default announcement;

放一张访问正常图