react native network lost check

Question

how to check react-native network lost connection? I tried the below code and its throwing an error. I want to display and alert when app lost it's network connection?

  CheckConnectivity = () => {
    // For Android devices
    if (Platform.OS === "android") {
      NetInfo.isConnected.fetch().then(isConnected => {
        console.log(isConnected,">>>")
        if (isConnected) {
          Alert.alert("You are online!");
        } else {
          Alert.alert("You are offline!");
        }
      });
    } else {
      // For iOS devices
      NetInfo.isConnected.addEventListener(
        "connectionChange",
        this.handleFirstConnectivityChange
      );
    }
  };

  handleFirstConnectivityChange = isConnected => {
    NetInfo.isConnected.removeEventListener(
      "connectionChange",
      this.handleFirstConnectivityChange
    );

    if (isConnected === false) {
      Alert.alert("You are offline!");
    } else {
      Alert.alert("You are online!");
    }
  };

Answer 1

It looks like you are using the wrong API. For example, this is for WEB

NetInfo.isConnected.removeEventListener

If you check it here: https://github.com/react-native-netinfo/react-native-netinfo/blob/ba5c22cf2045b690243984a548ee25f4f6371e4a/src/internal/nativeModule.web.ts#L59

You need to follow this examples:

https://github.com/react-native-netinfo/react-native-netinfo/blob/master/example/IsConnected.tsx

https://github.com/react-native-netinfo/react-native-netinfo/blob/master/example/ConnectionInfoSubscription.tsx