React-无法使用容器组件中定义的函数更改子组件的状态

// 容器组件
class Container extends React.Component {
  constructor(props) {
    super(props);
    this.state = {
      count: 0
    };
  }

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

  render() {
    return <ChildComponent updateCount={this.updateCount} />;
  }
}

// 子组件
class ChildComponent extends React.Component {
  handleClick = () => {
    const newCount = this.props.count + 1;
    this.props.updateCount(newCount);
  }

  render() {
    return <button onClick={this.handleClick}>增加计数</button>;
  }
}

// 容器组件
const CountContext = React.createContext();

class Container extends React.Component {
  constructor(props) {
    super(props);
    this.state = {
      count: 0
    };
  }

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

  render() {
    return (
      <CountContext.Provider value={{ count: this.state.count, updateCount: this.updateCount }}>
        <ChildComponent />
      </CountContext.Provider>
    );
  }
}

// 子组件
class ChildComponent extends React.Component {
  static contextType = CountContext;

  handleClick = () => {
    const newCount = this.context.count + 1;
    this.context.updateCount(newCount);
  }

  render() {
    return <button onClick={this.handleClick}>增加计数</button>;
  }
}