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？它显示错误：“_TypeError（类型‘Null’不是类型‘String’的子类型）”在 readUserRideRequestInformation 中

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);
    });
  }

功能

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,
  });
}

enter image description here

我如何解决它？

Answer 1

除了使用 bang !，您还可以进行 null 检查，或者使用字符串格式传递 null。

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