React native 不变冲突：模块AppRegistry不是已注册的可调用模块（调用UnununtapplicationComponentAtrottag）

index.js

import {AppRegistry} from 'react-native';
import TabBar from './src/Navigation/TabBar';
import {name as appName} from './app.json';

import App from './App';

AppRegistry.registerComponent(appName, () => App);

App.js

import { Platform }                 from 'react-native';
//component cycle
import TabBar                       from './src/Navigation/TabBar'
//External Library
import SplashScreen                 from 'react-native-splash-screen'
import codePush from "react-native-code-push";
//For Redux
import { PersistGate }              from 'redux-persist/integration/react'
import { Provider }                 from 'react-redux'
import store, { persistor }         from './store'

class App extends Component {

    componentDidMount() {
        SplashScreen.hide();
    }

    componentWillMount() {
      codePush.disallowRestart();
    }

    render() {
        return (
          <Provider store={store}>
            <PersistGate loading={null} persistor={persistor}> 
                <TabBar />
            </PersistGate>
          </Provider>
        );
    }
    
}

从'react native'导入{Platform}；
//成分循环
从“./src/Navigation/TabBar”导入TabBar
//外部图书馆
从“反应本机启动屏幕”导入启动屏幕
从“反应本机代码推送”导入代码推送；
//对于Redux
从“redux persist/integration/react”导入{PersistGate}
从“react redux”导入{Provider}
导入存储，{persistor}来自“/store”
类应用程序扩展组件{
componentDidMount（）{
SplashScreen.hide（）；
}
组件willmount（）{
codePush.DisallowArt（）；
}
render（）{
返回(
);
}
}

所以请告诉我如何清除错误我已经从项目中清除了缓存，但是我得到了相同的错误

错误不变冲突：模块AppRegistry不是已注册的可调用模块（调用 运行（应用程序） 错误不变冲突：模块AppRegistry不是已注册的可调用模块（调用UnuntapplicationComponentAtrottag）

您尚未使“应用”组件可导出

尝试此操作并添加“导出默认值”

export default class App extends Component