Question

我希望console.log('Refresh')每次路由更改时都会运行（从Component1切换到Component2）。但这只是在第一次渲染时触发。为什么？

index.js ：

import React from 'react';
import ReactDOM from 'react-dom';
import App from './App';
import { BrowserRouter } from 'react-router-dom';

ReactDOM.render(<BrowserRouter><App /></BrowserRouter>, document.getElementById('root'));

App.js ：

import React, { useEffect } from 'react';
import { Switch, Route } from 'react-router-dom';
import Nav from './Nav';
import Component1 from './Component1';
import Component2 from './Component2';

const App = () => {

  useEffect( () => console.log('Refresh'));

  return (
        [<Switch>
            <Route                            component = {Nav}/>
        </Switch>,
        <Switch>
            <Route exact path = '/component1' component = {Component1}/>
            <Route exact path = '/component2' component = {Component2}/>
        </Switch>]
  );
}

export default App;

Nav.js ：

import React from 'react';
import { Link } from 'react-router-dom';

const  Nav = () => {
  return (
    <div>
        <Link to = '/component1'>Component 1</Link>
        <Link to = '/component2'>Component 2</Link>
    </div>
  );
}

export default Nav;

Component1.js ：

import React from 'react';

const  Component1 = () => {

  return (
    <div>
        <p>Hi</p>
    </div>
  );
}

export default Component1;

Component2.js ：

import React from 'react';

const  Component2 = () => {
  return (
    <div>
        <p>Bye</p>
    </div>
  );
}

export default Component2;

Answer 1

使用key属性，以便每次我们渲染新组件（不同的键）

<Route path='/mypath/:username' exact render= {routeProps =><MyCompo {...routeProps} key={document.location.href} />} />

Answer 2

使用第二个参数useEffect有条件地应用效果。例如，通过react-router-dom，您可以获得一些属性

const { schoolId, classId } = props

useEffect(() => {
   // fetch something here
}, [schoolId, classId)

此处[schoolId, classId充当useEffect触发的唯一标识符。

Answer 3

useEffect不会被触发，因为App组件没有被重新渲染，该组件没有任何变化（没有状态或道具更新）。

如果您希望在更改路线时重新渲染App组件，则可以使用withRouter HOC来注入路线道具，如下所示：

import { Switch, Route, withRouter } from 'react-router-dom';

const App = () => {

  useEffect( () => console.log('Refresh'));

  return (...);
}

export default withRouter(App);

示例：https://codesandbox.io/s/youthful-pare-n8p1y

React useEffect不会在路线更改时触发

3 个答案: