Flutter中background_locator_2插件Android端跨Isolate传LocationDto报错

问题概述 #

使用background_locator_2（版本2.0.6-dev.2）实现后台位置获取功能，iOS端运行正常，但在Flutter和Kotlin版本更新后，Android端出现隔离间通信错误，错误信息如下：

[ERROR:flutter/runtime/dart_vm_initializer.cc(41)] Unhandled Exception: Invalid argument: is a regular instance: Instance of 'LocationDto'
E/flutter (26006): #0      _SendPort._sendInternal (dart:isolate-patch/isolate_patch.dart:249:43)
E/flutter (26006): #1      _SendPort.send (dart:isolate-patch/isolate_patch.dart:230:5)
E/flutter (26006): #2      LocationServiceRepository.callback
package:drivers_app/tabPages/location_service_reposirtory.dart:59

错误指向LocationServiceRepository类中send?.send(locationDto);一行，原因是Dart隔离间仅支持传递可序列化对象（基本类型、List、Map或实现序列化协议的类），而LocationDto是普通实例，无法直接跨隔离间传递。

解决方案 #

方案1：将LocationDto转换为Map传递 #

修改LocationServiceRepository的callback方法，把LocationDto转为Map后发送，接收端再重建对象：

@pragma('vm:entry-point')
Future<void> callback(LocationDto locationDto) async {
  print('$_count location in dart: ${locationDto.toString()}');
  await setLogPosition(_count, locationDto);
  final SendPort? send = IsolateNameServer.lookupPortByName(isolateName);
  
  // 转换LocationDto为Map
  final locationMap = {
    'latitude': locationDto.latitude,
    'longitude': locationDto.longitude,
    'accuracy': locationDto.accuracy,
    'altitude': locationDto.altitude,
    'speed': locationDto.speed,
    'speedAccuracy': locationDto.speedAccuracy,
    'heading': locationDto.heading,
    'time': locationDto.time,
    'isMocked': locationDto.isMocked,
  };
  send?.send(locationMap); // 发送Map替代原对象
  _count++;
}

接收端updateUI方法重建LocationDto：

Future<void> updateUI(dynamic data) async {
  if (data is Map) {
    final locationDto = LocationDto(
      latitude: data['latitude'],
      longitude: data['longitude'],
      accuracy: data['accuracy'],
      altitude: data['altitude'],
      speed: data['speed'],
      speedAccuracy: data['speedAccuracy'],
      heading: data['heading'],
      time: data['time'],
      isMocked: data['isMocked'],
    );
    await _updateNotificationText(locationDto);
  }
}

方案2：让LocationDto实现序列化 #

通过json_serializable包让LocationDto支持序列化，适用于需要完整传递对象的场景：

1. 依赖配置（pubspec.yaml）：

dependencies:
  json_annotation: ^4.8.1

dev_dependencies:
  build_runner: ^2.4.4
  json_serializable: ^6.7.0

2. 修改LocationDto类（若为插件类，可复制到本地修改）：

import 'package:json_annotation/json_annotation.dart';

part 'location_dto.g.dart';

@JsonSerializable()
class LocationDto {
  final double latitude;
  final double longitude;
  final double accuracy;
  final double altitude;
  final double speed;
  final double speedAccuracy;
  final double heading;
  final int time;
  final bool isMocked;

  LocationDto({
    required this.latitude,
    required this.longitude,
    required this.accuracy,
    required this.altitude,
    required this.speed,
    required this.speedAccuracy,
    required this.heading,
    required this.time,
    required this.isMocked,
  });

  factory LocationDto.fromJson(Map<String, dynamic> json) => _$LocationDtoFromJson(json);
  Map<String, dynamic> toJson() => _$LocationDtoToJson(this);
}

3. 生成序列化代码：

flutter pub run build_runner build

4. 修改发送和接收逻辑：

// 发送端
send?.send(locationDto.toJson());

// 接收端
Future<void> updateUI(dynamic data) async {
  if (data is Map) {
    final locationDto = LocationDto.fromJson(data.cast<String, dynamic>());
    await _updateNotificationText(locationDto);
  }
}

方案3：仅传递所需字段 #

若仅需部分字段（如经纬度），可直接传递单个字段或精简Map：

// 发送端
send?.send({
  'lat': locationDto.latitude,
  'lng': locationDto.longitude,
});

// 接收端
Future<void> updateUI(dynamic data) async {
  if (data is Map) {
    await BackgroundLocator.updateNotificationText(
      title: "Your location is updated",
      msg: "${DateTime.now()}",
      bigMsg: "${data['lat']}, ${data['lng']}",
    );
  }
}

内容的提问来源于stack exchange，提问作者Pannam