Google cloud firestore firebase.firestore不是一个函数。（在'；firebase.firestore（）'；中，'；firebase.firestore'；未定义）（设备）

我在这方面确实是新手，但我遵循了一个示例（），该示例一直工作到上周，现在如果我尝试在android或ios上进行模拟，就会出现此错误，因为在web上工作得很好

我创建了一个文件夹数据库来放置firebaseConfig

// database/firebaseDb.js

import * as firebase from 'firebase';
import firestore from '@firebase/firestore'

const firebaseConfig = {
     apiKey: "xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx",
     authDomain: "reactnativefirebase-00000.firebaseapp.com",
     databaseURL: "https://reactnativefirebase-00000.firebaseio.com",
     projectId: "reactnativefirebase-00000",
     storageBucket: "reactnativefirebase-00000.appspot.com",
     messagingSenderId: "000000000000000",
     appId: "1:000000000000000:web:000000000000000"

};

firebase.initializeApp(firebaseConfig);

firebase.firestore();

export default firebase;

在屏幕上我用了这个火炉店

// screens/AddUserScreen.js

import React, { Component } from 'react';
import { Button, StyleSheet, TextInput, ScrollView, ActivityIndicator, View } from 'react-native';
import firebase from '../database/firebaseDb';

class AddUserScreen extends Component {
  constructor() {
    super();
    this.dbRef = firebase.firestore().collection('users');
    this.state = {
      name: '',
      email: '',
      mobile: '',
      isLoading: false
    };
  }
(....)

}

有人能帮我吗