我正在完成一个应用程序的教程，当在前端工作时，我为导航栏制作了一个单独的文件：

import React, { Component } from 'react'

class Navbar extends Component {

 
  render() {
    return (
     <nav className="navbar navbar-dark fixed-top bg-dark flex-md-nowrap p-0 shadow">
          <a
            className="navbar-brand col-sm-3 col-md-2 mr-0"
            href="http://www.dappuniversity.com/bootcamp"
            target="_blank"
            rel="noopener noreferrer"
          >
            EthSwap
          </a>
        </nav>
    );
  }
}

export default Navbar;

我已将此文件导入到App.js文件中：

import React, { Component } from 'react'
import Web3 from 'web3'
import Navbar from ' ./Navbar'
import './App.css'

当我保存并重新加载网页时，出现以下错误：
页面没有找到！无法解析“C：\Users\34632\eth_swap1\src\components”中的.“/导航栏”
我不知道是甚么问题，因为我昨天已顺利地过了这一关，但现在问题仍然存在，有没有人知道这是甚么情况？

这是我的电话簿。
下面是App.js文件

import React, { Component } from 'react'
import Web3 from 'web3'
import from ' ./Navbar'
import './App.css'

class App extends Component {

  async componentWillMount()  {
    await this.loadWeb3()
    await this.loadBlockchainData()

  }

  async loadBlockchainData() {
    const web3 = window.web3

    const accounts = await web3.eth.getAccounts()
    this.setState({ account: accounts[0] })

    const ethBalance = await web3.eth.getBalance(this.state.account)
    this.setState({ ethBalance })
    console.log(this.state.ethBalance)

  }

  async loadWeb3() {
    if (window.ethereum) {
      window.web3 = new Web3(window.ethereum)
      await window.ethereum.enable()
    }
    else if (window.web3) {
      window.web3 = new Web3(window.web3.currentProvider)
    }
    else {
      window.alert('Non-Ethereum browser detected. You should consider trying Metamask!')
    }
  }

  constructor(props) {
    super(props)
    this.state = {
      account: '',
      ethBalance: '0'
       

    }

  }

  render() {
    console.log(this.state.account)
    return (
      <div>
        <Navbar />
        <div className="container-fluid mt-5">
          <div className="row">
            <main role="main" className="col-lg-12 d-flex text-center">
              <div className="content mr-auto ml-auto">
                <a
                  href="http://www.dappuniversity.com/bootcamp"
                  target="_blank"
                  rel="noopener noreferrer"
                >
              
                </a>
                <h1>Hello World!</h1>
               
              </div>
            </main>
          </div>
        </div>
      </div>
    );
  }
}

export default App;