content: import React from 'react';
  import { Link } from 'react-router';
  import './style.css';
  
  const Header = () => (
    <header className="mdl-layout__header">
      <div className="mdl-layout__header-row">
        <span className="mdl-layout-title">My Todo App</span>
        <div className="mdl-layout-spacer"></div>
        <nav className="mdl-navigation">
          <Link className="mdl-navigation__link" to="/">首页</Link>
          <Link className="mdl-navigation__link" to="/todo">登录</Link>
          <Link className="mdl-navigation__link" to="/about">关于我们</Link>
        </nav>
      </div>
    </header>
  );
  
  export default Header;
  