React-Native：将组件导入 App.js 时出错答案

【问题标题】：React-Native : error while import component to App.jsReact-Native：将组件导入 App.js 时出错
【发布时间】：2018-08-31 07:11:00
【问题描述】：

从组件导入默认类时出错使用expo，我搜索了这个错误但没有解决解决方案，组件返回对象。

type is invalid -- expected a string (for built-in components) or a class/function (for composite components) 但得到：对象

错误：

12:19:03: Warning: React.createElement: type is invalid -- expected a string (for built-in components) or a class/function (for composite components) but got: object. You likely forgot to export your component from the file it's defined in, or you might have mixed up default and named imports.

Check your code at registerRootComponent.js:35.
    in ExpoRootComponent (at renderApplication.js:33)
    in RCTView (at View.js:60)
    in View (at AppContainer.js:102)
    in RCTView (at View.js:60)
    in View (at AppContainer.js:122)
    in AppContainer (at renderApplication.js:32)

App.js

import Login from './app/components/login';

app/components/login/index.js

import React, {Component} from 'react';
import {Text, View} from 'react-native';

export default class Login extends Component {
    constructor(props){
        super(props);
        this.state = {}
    }
    render(){
        return(
            <View>
             <Text>Login</Text>
            </View>
        )
    }
}

【问题讨论】：

标签： javascript reactjs react-native

【解决方案1】：

在App.js 中使用Login 组件的默认导入。另外，从App.js导出一个根组件

import React from "react";
import Login from './app/components/login';

export default class App extends React.Component {
  render() {
    return <Login/>;
  }
}

【讨论】：

没什么，只有一行import。