如何让NetInfo与expo-web协同工作？

Question

我尝试使用expo文档中的NetInfo示例：https://docs.expo.io/versions/latest/sdk/netinfo/

当我为web编译时，编译失败，出现以下错误：

TypeError: NetInfo.addEventListener is not a function
(anonymous function)
..components/OfflineFullScreen.jsx:22

  21 | 
> 22 |    const unsubscribe = NetInfo.addEventListener((state) => {
     | ^  23 |      console.log('Connection type', state.type);
  24 |      console.log('Is connected?', state.isConnected);
  25 |    });

即使文档声明它应该被支持。

我的屏幕看起来是这样的：

import React, { useEffect, useState } from 'react';
import {
  View, Text, StyleSheet, ActivityIndicator,
} from 'react-native';
// import NetInfo from '@react-native-community/netinfo';
import * as NetInfo from '@react-native-community/netinfo';

const OfflineNotice = () => {
  const [connected, setConnected] = useState(true);


  useEffect(() => {

    /* const unsubscribe = NetInfo.addEventListener((state) => {
      if (state.isConnected) {
        setConnected(true);
      } else {
        setConnected(false);
      }
    }); */

    const unsubscribe = NetInfo.addEventListener((state) => {
      console.log('Connection type', state.type);
      console.log('Is connected?', state.isConnected);
    });

    return unsubscribe();
  }, []);

  if (!connected) { // if not connected return an full sized overlay
    return (
      <View style={styles.offlineContainer}>
        <ActivityIndicator size="large" color="darkorange" />
        <Text style={styles.offlineText}>No Internet Connection</Text>
        <Text style={styles.offlineText}>Trying to reconnect ...</Text>
      </View>
    );
  }
  return null;
};

const styles = StyleSheet.create({
  offlineContainer: {
    alignItems: 'center',
    justifyContent: 'center',
    position: 'absolute',
    position: 'absolute',
    left: 0,
    top: 0,
    opacity: 0.85,
    backgroundColor: 'black',
    width: '100%',
    height: '100%',
    zIndex: 100,
  },
  offlineText: {
    color: '#fff',
    marginTop: '3%',
  },
});

export default OfflineNotice;

你知道我做错了什么吗？这可能是个bug，因为expo-web还处于测试阶段？

我使用的是Expo SDK 37，@react-native-community/netinfo@4.6.0，

Answer 1

在React Native Web中，使用的是过时的Netinfo版本。这可以通过添加一个类似下面的代码的polyfill来解决。

import { useEffect, useState, useCallback } from 'react';
import { Platform } from 'react-native';
import NetInfo from 'react-native-web/dist/exports/NetInfo';

function useOldNetInfo() {
  const [netInfo, setNetInfo] = useState<NetInfo.NetInfoState>({});
  const [isConnected, setIsConnected] = useState<boolean>(true);

  const onInfo = useCallback((data) => {
    setNetInfo({ ...data, isConnected });
  }, [isConnected]);

  useEffect(() => {
    NetInfo.getConnectionInfo().then(onInfo);
    NetInfo.isConnected.fetch().then(setIsConnected);
    return NetInfo.addEventListener('connectionChange', onInfo).remove;
  }, [onInfo]);

  return netInfo;
}

export default Platform.select({
  web: useOldNetInfo,
  ios: CommunityNetInfo.useNetInfo,
  android: CommunityNetInfo.useNetInfo,
});

Github问题：https://github.com/expo/expo/issues/8070