React Native & Redux :未定义不是对象(计算'state.counter')

const initialState = {
  counter: 0
};

function reducer(state = initialState, action) {
  // 处理不同的action类型
  return state;
}

import { connect } from 'react-redux';

class MyComponent extends React.Component {
  render() {
    const { counter } = this.props;
    // 使用counter属性进行渲染
    return (
      <Text>{counter}</Text>
    );
  }
}

const mapStateToProps = state => ({
  counter: state.counter
});

export default connect(mapStateToProps)(MyComponent);

import { connect } from 'react-redux';
import { incrementCounter } from './actions';

class MyComponent extends React.Component {
  handleIncrement = () => {
    this.props.incrementCounter();
  };

  render() {
    // 渲染组件的其他部分
  }
}

const mapDispatchToProps = {
  incrementCounter
};

export default connect(null, mapDispatchToProps)(MyComponent);