在React类组件中使用ResizeObserver

import React, { Component } from 'react';

class ResizeObserverExample extends Component {
  constructor(props) {
    super(props);
    this.ref = React.createRef();
    this.state = {
      width: 0,
      height: 0,
    };
  }

  componentDidMount() {
    const observer = new ResizeObserver((entries) => {
      for (let entry of entries) {
        this.setState({
          width: entry.contentRect.width,
          height: entry.contentRect.height,
        });
      }
    });

    if (this.ref.current) {
      observer.observe(this.ref.current);
    }

    this.observer = observer;
  }

  componentWillUnmount() {
    if (this.observer) {
      this.observer.disconnect();
    }
  }

  render() {
    return (
      <div ref={this.ref} style={{ width: '200px', height: '200px', border: '1px solid black' }}>
        <p>Width: {this.state.width}px</p>
        <p>Height: {this.state.height}px</p>
      </div>
    );
  }
}

export default ResizeObserverExample;