错误：_TypeError（类型“Null”不是类型“String”的子类型）

Question

我需要在哪里解决这个问题？ 它在readUserRideRequestInformation 中显示错误：“_TypeError（类型‘Null’不是类型‘String’的子类型）”

class PushNotificationSystem
{
  FirebaseMessaging messaging = FirebaseMessaging.instance;

  Future initializeCloudMessaging(BuildContext context) async
  

    FirebaseMessaging.onMessageOpenedApp.listen((RemoteMessage? remoteMessage)
    {
      //display ride request information - user information who request a ride
      readUserRideRequestInformation(remoteMessage!.data["rideRequestId"], context);
    });
  }

function

import 'package:google_maps_flutter/google_maps_flutter.dart';

class UserRideRequestInformation
{
  LatLng? originLatLng;
  LatLng? destinationLatLng;
  String? originAddress;
  String? destinationAddress;
  String? rideRequestId;

  UserRideRequestInformation({
    this.originLatLng,
    this.destinationLatLng,
    this.originAddress,
    this.destinationAddress,
    this.rideRequestId,
  });
}

在此处输入图像描述

我如何解决它？

Answer 1

而不是使用 bang ! ，你可以做一个null校验，或者使用字符串格式来传递null。

 final rideRequestId = remoteMessage?.data["rideRequestId"];
 if(rideRequestId != null){
    readUserRideRequestInformation(rideRequestId, context);
  }