React卸载组件状态更新错误

import React, { Component } from 'react';

class MyComponent extends Component {
  constructor(props) {
    super(props);
    this.state = {
      data: null,
    };
    this.timer = null;
  }

  componentDidMount() {
    this.fetchData();
    this.timer = setInterval(this.fetchData, 1000);
  }

  componentWillUnmount() {
    clearInterval(this.timer);
  }

  fetchData = () => {
    // 模拟异步操作
    fetch('https://api.example.com/data')
      .then(response => response.json())
      .then(data => {
        // 在更新状态之前检查组件是否已被卸载
        if (this._isMounted) {
          this.setState({ data });
        }
      })
      .catch(error => {
        console.error(error);
      });
  }

  render() {
    // 渲染组件
  }
}

export default MyComponent;