使用后组件不渲染<link>点击

Question

I am new with React JS so I am sorry if this problem seems trivial.

I have set up a <Switch> along with a number of Routes in App.js to redirect and link components together. The first <Redirect> from App.js goes to ComponentA where when a div is clicked, it should go to ComponentB , but that is not the case. After some fiddling, I could get ComponentB to render but it was ALONG with ComponentA , and now with more changes, nothing shows up except the header .../componentB .

App.js

import { ComponentA, ComponentB } from './components/Component.js';
import { BrowserRouter as Router, Route, Redirect, Switch} from 'react-router-dom';

function App() {
  const [isLoggedIn, setIsLoggedIn] = useState(false);
  
  return (
    <div>
      <Router exact path="/">
        <Switch>
          <Route exact path="/componentA" component={ComponentA}/>
          <Route exact path="/componentB" component={ComponentB}/>      
          <Route exact path="/componentC" component={ComponentC}/>  
        </Switch>  
        {isLoggedIn ? <Redirect to="/componentA"/> : <Redirect to="/componentC"/>}
        // componentC is irrelevant to the question
      </Router>
    </div>
  );
}

ComponentA

import { BrowserRouter as Router, Route, Redirect, Switch} from 'react-router-dom';

function ComponentA() {  
  return (
    <div>
      <Router exact path="/">
        // ... code
        <Link exact to="/componentB">
           <div></div>
        </Link>
      </Router>
    </div>
  );
}

ComponentB (in the same file as ComponentA)

function ComponentB() {
  return (
    <div>Welcome to ComponentB</div>
  );
}

Answer 1

Issue

I think the second Router component rendered in ComponentA is jacking the link navigation. This "inner" routing context handles the navigation request and updates the URL in the address bar but doesn't allow the "outer" routing context to see the change and update the Route that is matched and rendered.

Solution

Remove the Router in ComponentA , also remove the exact prop from the Link as it's not a link prop.

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

function App() {  
  return (
    <div>
      // ... code
      <Link to="/componentB">
        <div></div>
      </Link>
    </div>
  );
}

Remove the exact and path props from Router , these are props for Route components.

import { ComponentA, ComponentB } from './components/Component.js';
import { BrowserRouter as Router, Route, Redirect, Switch} from 'react-router-dom';

function App() {
  const [isLoggedIn, setIsLoggedIn] = useState(false);
  
  return (
    <div>
      <Router>
        <Switch>
          <Route exact path="/componentA" component={ComponentA}/>
          <Route exact path="/componentB" component={ComponentB}/>      
          <Route exact path="/componentC" component={ComponentC}/>  
        </Switch>  
        {isLoggedIn ? <Redirect to="/componentA"/> : <Redirect to="/componentC"/>}
        // componentC is irrelevant to the question
      </Router>
    </div>
  );
}

Update

You need only one routing context for your application, typically a Router that wraps App component. Comb your code for any other nested Router components and remove them as these will mess with navigation as explained above.