250 lines
6.0 KiB
Markdown
250 lines
6.0 KiB
Markdown
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## React路由的使用
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使用React路由之前，我们需要先安装 `react-router-dom`这个包。比如：
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```
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yarn add react-router-dom
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```
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代码举例：
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（1）index.html
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```html
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<!DOCTYPE html>
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<html lang="en">
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<head>
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<meta charset="UTF-8">
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<meta name="viewport" content="width=device-width, initial-scale=1.0">
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<meta http-equiv="X-UA-Compatible" content="ie=edge">
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<title>Document</title>
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</head>
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<body>
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<!-- 容器，通过 React 渲染得到的 虚拟DOM，会呈现到这个位置 -->
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<div id="app"></div>
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</body>
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</html>
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```
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（2）main.js：
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```javascript
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// JS打包入口文件
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// 1. 导入包
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import React from "react";
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import ReactDOM from "react-dom";
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import App from "./App.jsx";
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// 使用 render 函数渲染 虚拟DOM
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ReactDOM.render(<App />, document.getElementById("app"));
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```
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（3）app.jsx:
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```java
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import React from "react";
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// 如果要使用 路由模块，第一步，运行 yarn add react-router-dom
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// 第二步，导入 路由模块
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// HashRouter 表示一个路由的跟容器，将来，所有的路由相关的东西，都要包裹在 HashRouter 里面，而且，一个网站中，只需要使用一次 HashRouter 就好了；
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// Route 表示一个路由规则， 在 Route 上，有两个比较重要的属性， path component
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// Link 表示一个路由的链接 ，就好比 vue 中的 <router-link to=""></router-link>
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import { HashRouter, Route, Link } from "react-router-dom";
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import Home from "./components/Home.jsx";
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import Movie from "./components/Movie.jsx";
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import About from "./components/About.jsx";
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export default class App extends React.Component {
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constructor(props) {
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super(props);
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this.state = {};
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}
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render() {
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// 当 使用 HashRouter 把 App 根组件的元素包裹起来之后，网站就已经启用路由了
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// 在一个 HashRouter 中，只能有唯一的一个根元素
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// 在一个网站中，只需要使用 唯一的一次 <HashRouter></HashRouter> 即可
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return (
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<HashRouter>
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<div>
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<h1>这是网站的APP根组件</h1>
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<hr />
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<Link to="/home">首页</Link>
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<Link to="/movie">电影</Link>
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<Link to="/about">关于</Link>
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<hr />
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{/* Route 创建的标签，就是路由规则，其中 path 表示要匹配的路由，component 表示要展示的组件 */}
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{/* 在 vue 中有个 router-view 的路由标签，专门用来放置，匹配到的路由组件的，但是，在 react-router 中，并没有类似于这样的标签，而是 ，直接把 Route 标签，当作的 坑（占位符） */}
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{/* Route 具有两种身份：1. 它是一个路由匹配规则； 2. 它是 一个占位符，表示将来匹配到的组件都放到这个位置 */}
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<Route path="/home" component={Home} />
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<hr />
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<Route path="/movie" component={Movie} />
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<hr />
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<Route path="/about" component={About} />
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</div>
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</HashRouter>
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);
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}
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}
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```
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（4）ReactDemo/src/components/Home.jsx
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```java
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import React from "react";
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export default class Home extends React.Component {
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constructor(props) {
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super(props);
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this.state = {};
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}
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render() {
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return <div>Home组件</div>;
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}
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}
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```
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（5）ReactDemo/src/components/Movie.jsx
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```java
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import React from "react";
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export default class Movie extends React.Component {
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constructor(props) {
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super(props);
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this.state = {};
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}
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render() {
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return <div>Movie组件</div>;
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}
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}
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```
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（6）ReactDemo/src/components/About.jsx
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```java
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import React from "react";
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export default class About extends React.Component {
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constructor(props) {
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super(props);
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this.state = {};
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}
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render() {
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return <div>About组件</div>;
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}
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}
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```
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运行结果：
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20190214_1000.png
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## 匹配路由参数
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### 模糊匹配与精准匹配
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我们在上面的代码中，进一步修改。假设 Movie 这个组件修改成这种路由匹配方式：
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```html
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<Link to="/movie/top250">电影</Link>
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<Route path="/movie" component={Movie} />
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```
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上面这种匹配方式，也是可以成功匹配到的。这是为啥呢？
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这是因为：默认情况下，路由中的匹配规则，是**模糊匹配**的。如果 路由可以部分匹配成功，就会展示这个路由对应的组件。
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如果想让路由规则，进行**精确匹配**，可以为Route添加 `exact` 属性。比如下面这种写法，因为是开启了精准匹配，所以是匹配不到的：（无法匹配）
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```html
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<Link to="/movie/top250/20">电影</Link>
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<Route path="/movie/" component={Movie} exact/>
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```
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另外，如果要匹配参数，可以在匹配规则中，使用 `:` 修饰符，表示这个位置匹配到的是参数。举例如下：（匹配正常）
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```html
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<Link to="/movie/top250/20">电影</Link>
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<Route path="/movie/:type/:id" component={Movie} exact/>
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```
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### 获取路由参数
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继续修改上面的代码。如果我想在 Movie 组件中显示路由中的参数，怎么做呢？
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我们可以通过 `props.match.params`获取路由中的参数。举例做法如下：
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app.jsx中的匹配规则如下：
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```html
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<Link to="/movie/top100/5">电影</Link>
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<Route path="/movie/:type/:id" component={Movie} exact/>
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```
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Moivie 组件的写法如下：
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```java
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import React from "react";
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export default class Movie extends React.Component {
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constructor(props) {
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super(props);
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this.state = {
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routeParams: props.match.params // 把路由中的参数保存到 state 中
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};
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}
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render() {
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console.log(this);
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// 如果想要从路由规则中，提取匹配到的参数，进行使用，可以使用 this.props.match.params.*** 来访问
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return (
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<div>
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{/* Movie --- {this.props.match.params.type} --- {this.props.match.params.id} */}
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Movie --- {this.state.routeParams.type} --- {this.state.routeParams.id}
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</div>
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);
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}
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}
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```
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打印结果如下：
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20190214_1030.png
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工程文件：
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2019-02-14-ReactDemo.zip
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