构建React应用时路由不起作用

Question

我创建了react app react router 4，但是我使用npm run build路由URL无法构建我的项目并显示404页面。如何解决该问题？我不知道。这是我的代码

import React from "react";
import ReactDOM from "react-dom";
import registerServiceWorker from "./registerServiceWorker";
import { BrowserRouter as Router } from "react-router-dom";
/* Material UI Components */
import { createMuiTheme, MuiThemeProvider } from "@material-ui/core/styles";
/* Styles */
import "react-datepicker/dist/react-datepicker-cssmodules.css";
import "./styles/main.scss";
/* Components */

import App from "../App";
import AdminHome from "../pages/admin/home";
import Login from "../pages/login";
import PrivateRoute from "./privateRoute";

/* App Theme */

const theme = createMuiTheme({
    palette: {
        type: "dark"
    }
});

ReactDOM.render((
    <Router>
        <MuiThemeProvider theme={theme}>
            <Switch>
                <PrivateRoute exact path={"/"} component={App}/>
                <PrivateRoute path={"/admin"} component={AdminHome}/>
                <Route path={"/login"} component={Login}/>
                <Route render={() => <p>Not Found</p>}/>
            </Switch>
        </MuiThemeProvider>
    </Router>
), document.getElementById("root"));
registerServiceWorker();

有人可以帮我解决这个问题吗？