一. url是什么：访问不同url, 展示不同的组件
二. 使用步骤：

1. 安装React路由：命令行中执行npm install react-router-dom --save(注意此处的版本为npm install react-router-dom@4.3.1 --save)
2. 两个js文件，分别为list.js和newButton.js,要实现访问localhost:3000/button的时候就显示button.js；访问localhost:3000/list的时候就显示list.js。代码如下：
   list.js

import React, {Component} from "react";

import {List} from 'antd';

const data = [
    'aaa',
    'bbb',
    'ccc',
    'ddd'
]
class List extends Component {
    render() {
        return (
            <List style={{marginLeft: 20,
            marginTop: 20,
            marginRight: 20}}
            header={<div>Header</div>}
            footer={<div>Footer</div>}
            bordered
            dataSource={data}
            renderItem={item=>(<List.Item>{item}</List.Item>)}
            />
        )
    }
}

export default List

newButton.js

import React, {Component} from "react";

import {List} from 'antd';

const data = [
    'aaa',
    'bbb',
    'ccc',
    'ddd'
]
class NewList extends Component {
    render() {
        return (
            <List style={{marginLeft: 20,
            marginTop: 20,
            marginRight: 20}}
            header={<div>Header</div>}
            footer={<div>Footer</div>}
            bordered
            dataSource={data}
            renderItem={item=>(<List.Item>{item}</List.Item>)}
            />
        )
    }
}

export default NewList

3. 在index.js中使用router
   1)引入路由：import { BrowserRouter, Route, Link } from 'react-router-dom';
   2)渲染BrowserRouter组件,其中包含一条条的路由

class Entry extends Component {
    render() {
        return (
            <BrowserRouter>
            <div>
            <Route path='/list' component={NewList}/>
            <Route path='/button' component={NewButton}/>
            </div>
            </BrowserRouter>
        )
    }
}

3）浏览器中输入localhost:3000后，什么后没显示出来，因为此时没有匹配的路由

4）根据路由的配置，浏览器中输入：localhost:3000/list就会显示newList组件
输入：localhost:3000/button就会显示newButton组件


注：BrowserRoute表示定义一个路由，Route表示一个路由项，
5）如想通过点击newButton里的按钮后跳转到列表页，需要用到Link（使用React路由后，就不能使用a标签进行页面跳转，需要借助Link标签完成路由的跳转）
步骤：在newButton中引入Link后用Link标签跳转
newButton.js

import React, {Component, Fragment} from "react";
import { Link } from "react-router-dom";

import {Button} from 'antd';

class NewButton extends Component {
    render() {
        return (
            <Link to='/list'>
                <Button type="primary">按钮</Button>
            </Link>
            
        )
    }
}

export default NewButton;

6)跳转页面的过程中，携带参数，如何获取参数，如

class NewButton extends Component {
    render() {
        return (
            <Link to='/list/123'>
                <Button type="primary">按钮</Button>
            </Link>
            
        )
    }
}

解决方式：在index.js配置路由部分，给list地址后加一个变量,表示传过来的值为变量id的值

<Route path='/list/:id' component={NewList}/>

之后在newList组件中打印出console.log(this.props)

可看到params里有变量id的值为123

完整代码如下：
index.js中

import React, {Component}from 'react';
import ReactDOM from 'react-dom';
import { BrowserRouter, Route } from 'react-router-dom';
import 'antd/dist/antd.css';
import NewList from './newList'
import NewButton from './newButton'

class Entry extends Component {
    render() {
        return (
            <BrowserRouter>
            <div>
            <Route path='/list/:id' component={NewList}/>
            <Route path='/button' component={NewButton}/>
            </div>
            </BrowserRouter>
        )
    }
}

// 将内容挂载到页面上
ReactDOM.render(<Entry />, document.getElementById('root'));

newList.js中

import React, {Component} from "react";

import {List} from 'antd';

const data = [
    'aaa',
    'bbb',
    'ccc',
    'ddd'
]
class NewList extends Component {
    render() {
        console.log(this.props)
        return (
            <List style={{marginLeft: 20,
            marginTop: 20,
            marginRight: 20}}
            header={<div>Header</div>}
            footer={<div>Footer</div>}
            bordered
            dataSource={data}
            renderItem={item=>(<List.Item>{item}</List.Item>)}
            />
        )
    }
}

export default NewList

newButton.js中

import React, {Component} from "react";
import { Link } from "react-router-dom";

import {Button} from 'antd';

class NewButton extends Component {
    render() {
        return (
            <Link to='/list/123'>
                <Button type="primary">按钮</Button>
            </Link>
            
        )
    }
}

export default NewButton;