问如何在ReactJS中获取文本字段的输入？我正在尝试制作一个特定的计算器，并需要用户的输入

EN

import "./StartPage.scss";
import React, { Component } from "react";
import InputCard from '../components/InputCard';
import {BrowserRouter as Router, Switch, Route, Link} from 'react-router-dom';
import ResultsPage from '../pages/ResultsPage';
import InputToFormula from "../components/InputToFormula";
import PropTypes from 'prop-types';

import { evaluate } from "mathjs";
import * as math from "mathjs";
import { tsConstructorType } from "@babel/types";

class StartPage extends Component {
  constructor(props) {
  super(props);

    this.state = {
      setBots: "",
      setEmployees: "",
      setSalary: "",
      setTime: ""
    };
  };
  
    handleBots = event => {
      this.setState({ setBots: event.target.value});
    };
    handleEmployees = event => {
      this.setState({ setEmployees: event.target.value});
    };
    handleSalary = event => {
      this.setState({ setSalary: event.target.value});
    };
    handleTime = event => {
      this.setState({ setTime: event.target.value});
    };
  
    logValue = () => {
      console.log(this.state.setBots);
    };

  render(){
    return (
      <div className="container">
        <div className="header-container">
          <h2>   </h2>
          <h1>Return on Investment Calculator</h1>
          <h2>   </h2>
        </div>
  
        <form>
        <div class="inputs input-group">
          <InputCard onEvent={this.handleBots} id="Bots" icon="robot" label="Number of Processes" />
          <InputCard onEvent={this.handleEmployees} id="Employees" icon="users" label="Number of FTE's" />
          <InputCard onEvent={this.handleSalary} id="Salary" icon="dollar-sign" label="Average Salary" />
          <InputCard onEvent={this.handleTime} id="Time" icon="clock" label="Average Time (%)" />
        </div>
        
        <Router>
          <div>
            <h1>   </h1>
            <Link to='/ResultsPage'><button onClick={this.logValue} type="button" 
            class="btn btn-outline-success submit-button btn-lg">CALCULATE</button></Link>
          </div>
          <Switch>
            <Route path="/ResultsPage" exact>
              <ResultsPage />  
            </Route>  
          </Switch>  
        </Router>
        </form>
  
      </div>
    );
  }
}


export default StartPage;