App.js

  useEffect(() => {
    AsyncStorage.getItem(savedUserKey)
      .then(async user => {
        try {
          if (user) {
            const authorizationStatus = await messaging().requestPermission();
            if (
              authorizationStatus === messaging.AuthorizationStatus.AUTHORIZED ||
              authorizationStatus === messaging.AuthorizationStatus.PROVISIONAL
            ) {
              if (Platform.OS === 'ios') {
                const token = await messaging().getAPNSToken();
                await sendbird.registerAPNSPushTokenForCurrentUser(token);
              } else {
                const token = await messaging().getToken();
                await sendbird.registerGCMPushTokenForCurrentUser(token);
              }
            }
          }
        } catch (err) {
          console.error(err);
        }
      })
      .catch(err => console.error(err));

    if (Platform.OS !== 'ios') {
      const unsubscribeHandler = messaging().onMessage(onRemoteMessage);
      return unsubscribeHandler;
    }
  }, []);