React Native 中的全局状态

React Native是一种流行的跨平台移动应用开发框架，它允许开发人员使用JavaScript编写一次代码，然后将其在iOS和Android等多个平台上运行。除了提供一些基本的组件和API之外，React Native还提供了一种全局状态管理机制，使得开发者可以更方便地管理应用程序的状态。

npm install redux react-redux redux-thunk

javascript
import { createStore, applyMiddleware } from 'redux';
import thunk from 'redux-thunk';
import rootReducer from './reducers';
const store = createStore(rootReducer, applyMiddleware(thunk));
export default store;

javascript
export const UPDATE_CART = 'UPDATE_CART';
export const updateCart = (items) => {
  return {
    type: UPDATE_CART,
    payload: items
  };
};

javascript
import { UPDATE_CART } from './actions';
const initialState = {
  cart: []
};
const rootReducer = (state = initialState, action) => {
  switch (action.type) {
    case UPDATE_CART:
      return {
        ...state,
        cart: action.payload
      };
    default:
      return state;
  }
};
export default rootReducer;

javascript
import React from 'react';
import { AppRegistry } from 'react-native';
import { Provider } from 'react-redux';
import App from './App';
import store from './store';
const ReduxApp = () => (
  
    
  
);
AppRegistry.registerComponent('ReduxApp', () => ReduxApp);

javascript
import React from 'react';
import { View, Text } from 'react-native';
import { connect } from 'react-redux';
const CartScreen = ({ cart }) => (
  
    Cart Items: {cart.length}
  
);
const mapStateToProps = (state) => {
  return {
    cart: state.cart
  };
};
export default connect(mapStateToProps)(CartScreen);