React实现顶部固定滑动式导航栏（导航条下拉一定像素时显示原导航栏样式）

import React from ‘react‘;
import ‘./App.css‘;
import { Link, Route } from ‘react-router-dom‘;
import { Layout } from ‘antd‘;

//引入导航栏相对应的组件
import Home from ‘./components/Home/Home‘;
import CoreTechnology from ‘./components/Technology/Technology‘;
import Case from ‘./components/Case/Case‘;
import About from ‘./components/About/About‘;
import Join from ‘./components/Join/Join‘;

const { Content } = Layout;

class App extends React.Component {

//在componentDidMount生命周期中添加window的handleScroll滑动监听事件
componentDidMount() {
  window.addEventListener(‘scroll‘, this.handleScroll);
}

//定义handleScroll事件函数
handleScroll =(e)=>{
  var header = document.getElementById(‘header‘); //定义一个dom节点为‘header‘的header变量
    if(window.pageYOffset >= 80){  //if语句判断window页面Y方向的位移是否大于或者等于导航栏的height像素值
      header.classList.add(‘header_bg‘);  //当Y方向位移大于80px时，定义的变量增加一个新的样式‘header_bg‘
    } else {
      header.classList.remove(‘header_bg‘); //否则就移除‘header_bg‘样式
    }
}

  render() {
    return (
      <div className="page" id="page">
        <Layout>
          <div className="header" id="header"> //导航栏div
            <div className="brand">
              <Link to="/">
                <img src={require("./img/dkgw_logo@01.png")} alt="大可logo" width="" height="32"/>
              </Link>
            </div>
            <div className="nav">
              <ul>
                <li>
                  <Link to="/technology">
                    <img src={require("./img/dkgw_hxjs.png")} alt="核心技术" width="32" height="32"/>
                    核心技术
                  </Link>
                </li>
                <li>
                  <Link to="/case">
                    <img src={require("./img/dkgw_hyal.png")} alt="行业案例" width="32" height="32"/>
                    行业案例
                  </Link>
                </li>
                <li>
                  <Link to="/about">
                    <img src={require("./img/dkgw_gywm.png")} alt="关于DUCK" width="32" height="32"/>
                    关于DUCK
                  </Link>
                </li>
                <li>
                  <Link to="/join">
                    <img src={require("./img/dkgw_jrwm.png")} alt="加入我们" width="32" height="32"/>
                    加入我们
                  </Link>
                </li>
              </ul>
            </div>
          </div>

          <Content className="content" id="content">
            <Route path="/" exact component={ Home }/>
            <Route path="/technology" component={ CoreTechnology }/>
            <Route path="/case" component={ Case }/>
            <Route path="/about" component={ About }/>
            <Route path="/join" component={ Join }/>
          </Content>
        </Layout>
      </div>
    );
  }
}

export default App;

    position: fixed;
    box-sizing: border-box; 
    display: flex;
    justify-content: space-between;
    align-items: center;
    transition: 0.5s;
    z-index: 1000;

@import ‘~antd/dist/antd.css‘; //引入antd样式
@import url(‘https://fonts.googleapis.com/css?family=Roboto‘); //引入谷歌字体样式

/* {通用样式开始} */
* {
    margin: 0;
    padding: 0;
    font-family: Arial, Helvetica, sans-serif;
    -webkit-box-sizing: border-box;
    -moz-box-sizing: border-box;
    box-sizing: border-box;
}
/* {通用样式结束} */

/* {导航栏基础样式} */
.header
{
    position: fixed;
    top: 0;
    left: 0;
    width: 100vw;
    height: 5rem;
    padding: 0 10vw;
    box-sizing: border-box;
    display: flex;
    justify-content: space-between;
    align-items: center;
    transition: 0.5s;
    z-index: 1000;
}

{/*{导航栏新样式}*/}
.header.header_bg
{
    background: #607d8b;
}

.nav ul
{
    margin: 0;
    padding: 0;
    display: flex;
}

.nav ul li
{
    list-style: none;
}

.nav ul li a 
{
    color: #fff;
    padding: 0 20px;
    font-size: 1.1em;
    text-decoration: none;
    font-weight: bold;
}

.brand a
{
    color: #fff;
    font-size: 1.1em;
    text-decoration: none;
    font-weight: bold;
}