我已经按照这个教程，我认为我已经做了一切所需的，但我仍然有这个警告：
未处理的承诺拒绝： 错误：操作必须是普通对象。实际类型为："Promise"。您可能需要向存储设置中添加中间件来处理其他值的分派，如"redux-thunk"来处理分派函数。有关示例，请参阅www.example.com和www.example.com。https://redux.js.org/tutorials/fundamentals/part-4-store#middleware and https://redux.js.org/tutorials/fundamentals/part-6-async-logic#using-the-redux-thunk-middleware for examples.
我的代码：
1.在store文件夹中，这是我的index.js文件：

import { createStore, applyMiddleware } from "redux";
import thunkMiddleware from "redux-thunk";
import { composeWithDevTools } from "redux-devtools-extension";
import rootReducer from "../reducers/index";

const composedEnhancer = composeWithDevTools(applyMiddleware(thunkMiddleware)); 
const store = createStore(rootReducer, composedEnhancer);
export default store;

在我的App.js文件中：

...
import store from "./redux/store/index";
...
return (
        <Provider store={store}>
          <NavigationContainer>
            <MainNavigator />
          </NavigationContainer>
        </Provider>
      );

在我的MainNavigator文件中：

import { connect } from "react-redux";
import { bindActionCreators } from "redux";
import {someAsyncFunctionFromRedux} from "../../redux/actions/index";
...
const MainComponent = (props) => {
  ...

  useEffect(() => {
    async function f() {
      await props.someAsyncFunctionFromRedux();
    }
    f();
  }, []);

在我的actions/index.js里

export async  function someAsyncFunction() {
   return  async (dispatch) => {
     await firebase
      .firestore()
      .collection("Users")
      .get()
      .then( (snapshot) => {
        let users = [];
        snapshot.docs.map((doc) => {
          const data = doc.data();
          const id = doc.id;
          users.push({id, ...data})
        })
        dispatch({ type: USERS_STATE_CHANGE, users });
      });
  };
}