React运行浏览器报错[Amay have only one child element]

错误信息

Uncaught Invariant Violation: A <Router> may have only one child element
    at invariant (http://localhost:8111/bundle.js:1071:15)
    at Router.componentWillMount (http://localhost:8111/bundle.js:2413:54)
    at callComponentWillMount (http://localhost:8111/bundle.js:27042:14)
    at mountClassInstance (http://localhost:8111/bundle.js:27135:5)
    at updateClassComponent (http://localhost:8111/bundle.js:30309:5)
    at beginWork (http://localhost:8111/bundle.js:31265:16)
    at performUnitOfWork (http://localhost:8111/bundle.js:34933:12)
    at workLoop (http://localhost:8111/bundle.js:34973:24)
    at renderRoot (http://localhost:8111/bundle.js:35056:7)
    at performWorkOnRoot (http://localhost:8111/bundle.js:35963:7)

解决方法

原来的demo

ReactDom.render(
    <BrowserRouter>
	    <Nav />
	    {getRouter()}
    </BrowserRouter>,
    document.getElementById('app')
)

解决后的demo(如果BrowserRouter中有多个组件需要在BrowserRouter加一层div)

ReactDom.render(
    <BrowserRouter>
        <div>
            <Nav />
            {getRouter()}
        </div>
    </BrowserRouter>,
    document.getElementById('app')
)

至于原因还没有去细节研究，如果有知道的小伙伴可以一起交流，或者直接在下面评论解释一下，谢谢，一起学习。