useDispatch() 错误:找不到 react-redux 上下文值；请确保组件被包裹在 <Provider> 中. [英] useDispatch() Error: Could not find react-redux context value; please ensure the component is wrapped in a <Provider>

问题描述

我正在尝试使用 React-Redux 库，但在标题上出现错误.我用 Provider 包装了我的组件，但我仍然收到错误，只有当我实现了 useDispatch() 钩子.

I am trygin to use React-Redux library and I am getting the error on the title. I wrapped my components with Provider but I still get the error, only if I implement the useDispatch() hook.

应用程序运行良好，直到我添加了 useDispatch() 行.可以删除有关调度函数的其余行，但我仍然遇到相同的错误.

The app worked fine, until I added the useDispatch() line. The rest of lines regarding the dispatch function can be removed and I still get the same error.

如果您能帮助我，我将不胜感激.谢谢

If you could help me I would really appreciate it. Thanks

这是我的代码:

import 'react-native-gesture-handler';
import {NavigationContainer} from '@react-navigation/native';
import Navigator from './navigation/Navigator';

import React, {useEffect, useState, useCallback} from 'react';
import {SafeAreaView, StyleSheet, Text, View} from 'react-native';

import {createStore, combineReducers} from 'redux';
import {Provider, useDispatch} from 'react-redux';
import dataReducer from './store/reducers/dataReducer';
import {CONSTANTS} from './constants/constants';
import {saveInitialData} from './store/actions/dataActions';

const App = () => {
  const [fetched, setFetched] = useState(initialState);

  const dispatch = useDispatch();

  const saveInitialDataHandler = useCallback(data => {
    dispatch(saveInitialData(data));
    callback;
  }, []);

  const rootReducer = combineReducers({
    content: dataReducer,
  });

  const store = createStore(rootReducer);

  useEffect(() => {
    fetchData();
  }, []);

  const fetchData = () => {
    fetch(CONSTANTS.database)
      .then(response => response.json())
      .then(responseJSON => {
        setFetched(true);
        saveInitialDataHandler(responseJSON);
      });
  };

  if (!fetched) {
    return (
      <Provider store={store}>
        <View stlye={{flex: 1, alignItems: 'center', justifyContent: 'center'}}>
          <Text></Text>
        </View>
      </Provider>
    );
  } else {
    return (
      <Provider store={store}>
        <NavigationContainer>
          <SafeAreaView style={styles.SafeAreaView}>
            <Navigator></Navigator>
          </SafeAreaView>
        </NavigationContainer>
      </Provider>
    );
  }
};

const styles = StyleSheet.create({
  SafeAreaView: {flex: 1},
});

export default App;

推荐答案

App 必须包含在 provider 中，因为您在其中使用了 useDispatch.现在只是个孩子.Provider 设置上下文，以便只有它的孩子可以访问它，而不是父母.

App must be wrapped in provider since you are using useDispatch in it. Right now it's just a child. Provider sets the context so only its children can have access to it, not a parent.

一种解决方案是为其创建一个包装器组件:

One solution would be to create a wrapper component for it:

const AppWrapper = () => {
  const store = createStore(rootReducer);

  return (
    <Provider store={store}> // Set context
      <App /> // Now App has access to context
    </Provider>
  )
}

const App = () => {
  const dispatch = useDispatch(); // Works!
...

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