React native 引用错误：Can'；找不到变量：组件

嗨，我想使用stack navigator，我已经将我的app.js文件更改为

   /**
 * Sample React Native App
 * https://github.com/facebook/react-native
 *
 * @format
 * @flow strict-local
 */

import React from 'react';
import Welcome1 from "./Pages/Start_Section/Welcome1.js"
import {createAppContainer} from "react-navigation"
import {createStackNavigator} from "react-navigation-stack"

const PushRouteOne = createStackNavigator(
{
    Page1: {
        screen: Welcome1,

    }
},

{
  initialRouteName: "Page1",
  mode: "modal",
  headerMode: "none",
  })


  const AppContainer = createAppContainer(PushRouteOne)

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

当我用另一个示例检查代码时，我不知道一切都是正确的

/**
 * @format
 */

    import {AppRegistry} from 'react-native';
    import App from './App';
    import {name as appName} from './app.json';
    import 'react-native-gesture-handler';
    
    AppRegistry.registerComponent(appName, () => App);