从子组件更新状态

// 父组件
class ParentComponent extends React.Component {
  constructor(props) {
    super(props);
    this.state = {
      count: 0,
    };
    this.updateCount = this.updateCount.bind(this);
  }

  updateCount(newCount) {
    this.setState({ count: newCount });
  }

  render() {
    return (
      <div>
        <h1>Count: {this.state.count}</h1>
        <ChildComponent onUpdate={this.updateCount} />
      </div>
    );
  }
}

// 子组件
class ChildComponent extends React.Component {
  constructor(props) {
    super(props);
    this.handleClick = this.handleClick.bind(this);
  }

  handleClick() {
    const newCount = this.props.count + 1;
    this.props.onUpdate(newCount);
  }

  render() {
    return <button onClick={this.handleClick}>Increase Count</button>;
  }
}