你应该研究一下Class component是如何工作的，只要花10分钟，我相信如果你有关于钩子的知识，你会很快习惯它。
这里是您所要求的示例，只是为了让您开始;

class YourClass extends React.Component {
  constructor(props) {
    super(props);
    this.state = {
      sidebar: 0 // this is a good place to set Initial value
    };
  }

  showSidebar = () => { // This is a method of the class, similar to your arrow f
    this.setState({ sidebar: !this.state.sidebar });
  };

  render() {
   return // render your things here, similar to what you "return" in hooks
   // You can use your this.state.sidebar value here, similar to "sidebar"
  }
}