未处理的异常:NoSuchMethodError:在 null 上调用了方法“[]"(无法在控制台上打印消息) [英] Unhandled Exception: NoSuchMethodError: The method '[ ]' was called on null( Not able to print Message on Console)

问题描述

这是我尝试从 firebase 消息传递消息时出现的错误，如果有人能向我解释如何使其正确，我会很高兴我正在使用旧的依赖项，但切换到新的依赖项会导致很多问题.

Here is the error when im trying to send the message from the firebase messaging i would be really glad if anyone could explain me this how to make it correct I was using old dependencies but swtiching to new is causing Alot of problem.

E/flutter (21035): [ERROR:flutter/lib/ui/ui_dart_state.cc(199)] Unhandled Exception: NoSuchMethodError: The method '[]' was called on null.
E/flutter (21035): Receiver: null
E/flutter (21035): Tried calling: []("ride_id")

这是我的pushnotification.dart:文件

import 'dart:io';
import 'package:cab_driver/globalvariables.dart';
import 'package:firebase_core/firebase_core.dart';
import 'package:firebase_database/firebase_database.dart';
import 'package:firebase_messaging/firebase_messaging.dart';
import '../main.dart';

class PushNotificationService {

  final FirebaseMessaging fcm = FirebaseMessaging.instance;

  Future initialize() async {
    FirebaseMessaging.instance.getInitialMessage();

    FirebaseMessaging.onMessage.listen((RemoteMessage message) async{

      FetchRiderInfo(getRideID(message.data));
    });

    FirebaseMessaging.onMessageOpenedApp.listen((RemoteMessage message) async{

      FetchRiderInfo(getRideID(message.data));

      });

    FirebaseMessaging.onBackgroundMessage(firebaseMessagingBackgroundHandler);

  }

  Future<String>getToken() async{

    String token = await fcm.getToken();
    print('token: $token');

    DatabaseReference tokenRef = FirebaseDatabase.instance.reference().child('drivers/${currentFirebaseUser.uid}/token');
    tokenRef.set(token);

    fcm.subscribeToTopic('alldrivers');
    fcm.subscribeToTopic('allusers');
  }

  String getRideID(Map<String, dynamic>message){

    String rideID = '';

    if(Platform.isAndroid) {
      rideID = message['data']['ride_id'];
    }
    else{
      rideID = message['data']['ride_id'];
      print('ride_id : $rideID');
    }
    return rideID;
  }

  void FetchRiderInfo(String rideId){
    DatabaseReference rideRef = FirebaseDatabase.instance.reference().child('rideRequest/$rideId');

    rideRef.once().then((DataSnapshot snapshot){

      if(snapshot.value != null){

        double pickupLat = double.parse(snapshot.value['location']['latitude'].toString());
        double pickupLng = double.parse(snapshot.value['location']['longitude'].toString());
        String pickupAddress = snapshot.value['pickup_address'].toString();

        double destinationLat = double.parse(snapshot.value['destination']['latitude'].toString());
        double destinationLng = double.parse(snapshot.value['destination']['longitude'].toString());
        String destinationAddress = snapshot.value['destination_address'];
        String paymentMethod = snapshot.value['payment_method'];


        print(pickupAddress);

      }
    });

  }
}

我想打印我从邮递员那里发送的消息，但给出的信息与 Unhandled Exception: NoSuchMethodError: The method '[]' was called on null. 任何人都可以提供帮助我真的卡住了，什么都不懂

I wanted to print the message which i'm sending from the postman but giving the same thing as Unhandled Exception: NoSuchMethodError: The method '[]' was called on null. plz anyone can help Im really stuck not understanding anything

推荐答案

打印message['data']并查看内容，好像没有ride_id.也请查看文档.

Print the message['data'] and check it contents, it seems it has no field called ride_id. Check the documentation as well.

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