在反应中保持状态和滚动位置

Question

我正在尝试构建一个显示博客文章列表的组件。当用户单击帖子时，它会呈现显示帖子详细信息的组件。但是当用户点击浏览器中的后退按钮时，带有帖子列表的前一个组件会重新呈现，并且它会丢失之前的状态和滚动位置。有没有办法可以保存以前的状态和滚动位置，以便当用户点击后退按钮时，它们处于相同的位置并且帖子列表不会重新呈现并且也不会丢失滚动位置？

这是我的博客列表组件代码：

import axios from "axios";
import { Link } from "react-router-dom";

class About extends React.Component {
  state = { posts: [] };

  componentDidMount() {
    axios.get("https://jsonplaceholder.typicode.com/posts").then(res => {
      this.setState({ posts: res.data.slice(0, 10) });
    });
  }

  render() {
    const { posts } = this.state;

    const postsList = posts.length ? (
      posts.map(post => {
        return (
          <div className="card" key={post.id}>
            <div className="card-body">
              <Link to={"/view/" + post.id}>
                <h5 className="card-title">{post.title}</h5>
              </Link>
              <p className="card-text">{post.body}</p>
            </div>
          </div>
        );
      })
    ) : (
      <div className="text-danger text-center">No Posts yet...</div>
    );

    return <div>{postsList}</div>;
  }
}

export default About;

这是我的博客详细信息组件：

import React from "react";
import { withRouter } from "react-router-dom";
import axios from "axios";

class PostDetail extends React.Component {
  state = { post: null };

  componentDidMount() {
    let id = this.props.match.params.post_id;

    axios.get("https://jsonplaceholder.typicode.com/posts/" + id).then(res => {
      this.setState({ post: res.data });
    });
  }

  render() {
    const post = this.state.post ? (
      <div className="card border-primary">
        <div className="card-header">{this.state.post.title}</div>
        <div className="card-body text-primary">
          <p className="card-text">{this.state.post.body}</p>
        </div>
      </div>
    ) : (
      <div className="text-center text-danger">Loading Post...</div>
    );

    return <div>{post}</div>;
  }
}

export default withRouter(PostDetail);

Answer 1

您必须state使用window.pageYOffset

this.setState({
    scrollPosition: window.pageYOffset
});

而一旦你点击后退按钮，你必须在方法中设置窗口位置componentDidMount。

window.scrollTo(0, this.state.scrollPosition);

默认情况下，您可以设置scrollPositionis的值0。

更新

sessionStorage出于演示目的，我在这里使用来保持滚动位置。您还可以使用上下文 API 或 redux 存储来管理它。

这是为您准备的工作演示。 https://stackblitz.com/edit/react-fystht

import React from "react";
import axios from "axios";
import { Link } from "react-router-dom";

class Posts extends React.Component {
  state = { posts: [] };

  componentDidMount() {
    axios.get("https://jsonplaceholder.typicode.com/posts").then(res => {
      this.setState({ posts: res.data.slice(0, 20) }, () => {
        this.handleScrollPosition();
      });
    });
  }

  // handle scroll position after content load
  handleScrollPosition = () => {
    const scrollPosition = sessionStorage.getItem("scrollPosition");
    if (scrollPosition) {
      window.scrollTo(0, parseInt(scrollPosition));
      sessionStorage.removeItem("scrollPosition");
    }
  };

  // store position in sessionStorage
  handleClick = e => {
    sessionStorage.setItem("scrollPosition", window.pageYOffset);
  };

  render() {
    const { posts } = this.state;

    const postsList = posts.length ? (
      posts.map(post => {
        return (
          <div className="card" key={post.id}>
            <div className="card-body">
              <Link to={"/view/" + post.id} onClick={this.handleClick}>
                <h5 className="card-title">{post.title}</h5>
              </Link>
              <p className="card-text">{post.body}</p>
            </div>
          </div>
        );
      })
    ) : (
      <div className="text-danger text-center">No Posts yet...</div>
    );

    return <div>{postsList}</div>;
  }
}

export default Posts;

希望能帮到你！

Answer 2

这是使用钩子（功能组件）的答案

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

const Posts = () => {
  const [posts, setPosts] = useState([]);
  const postsList = posts.length;

  useEffect(() => {
    axios.get('https://jsonplaceholder.typicode.com/posts').then((res) => {
      setPosts(res.data.slice(0, 20));
    });
  }, []);

  useEffect(() => {
    if (posts.length) {
      const scrollPosition = sessionStorage.getItem('scrollPosition');
      if (scrollPosition) {
        window.scrollTo(0, parseInt(scrollPosition, 10));
        sessionStorage.removeItem('scrollPosition');
      }
    }
  }, [posts]);

  return (
    <>
      {postsList ? (
        posts.map((post) => {
          return (
            <div className="card" key={post.id}>
              <div className="card-body">
                <Link
                  to={'/view/' + post.id}
                  onClick={() =>
                    sessionStorage.setItem('scrollPosition', window.pageYOffset)
                  }
                >
                  <h5 className="card-title">{post.title}</h5>
                </Link>
                <p className="card-text">{post.body}</p>
              </div>
            </div>
          );
        })
      ) : (
        <div className="text-danger text-center">No Posts yet...</div>
      )}

      <div>{postsList}</div>
    </>
  );
};

export default Posts;

https://stackblitz.com/edit/react-cbl7in?file=Posts.js