FlutterJNI detached from native C++

Hi,

First i would like to appreciate the effort put into developing this plugin and also the patience to respond to users issues. You guys are the best!

I am building a safety app that sends location updates when the phone is shook and that needs to work even while the app is in background.

I tried to use the flutter shake sensor plugin to trigger the location update when the phone is shook but whenever the app goes into background, i get the message:

W/FlutterJNI(27552): Tried to send a platform message to Flutter, but FlutterJNI was detached from native C++. Could not send. Channel: plugins.flutter.io/sensors/accelerometer. Response ID: 0

i would appreciate any help 🙏

My full code:

import 'dart:async';
import 'dart:isolate';

import 'dart:ui';

import 'package:flutter/material.dart';

import 'package:background_locator/background_locator.dart';
import 'package:background_locator/location_dto.dart';
import 'package:background_locator/location_settings.dart';
import 'package:shake/shake.dart';
import 'package:sentry/sentry.dart';
import 'package:trackamsos/background/SOSHandler.dart';
import 'package:trackamsos/background/ensureAlwaysBackground.dart';
import 'package:trackamsos/core/helpers/getShakeThresholdGravity.dart';

class BackgroundService {
  static final BackgroundService _backgroundService =
      BackgroundService._internal();
  static const String _isolateName = "LocatorIsolate";
  static final SOSHandler sosHandler = SOSHandler();
  static final ReceivePort port = ReceivePort();
  final SentryClient sentry = SentryClient(
      dsn:
          'https://XXXXXXXXXXXXXXXXXXXXX.ingest.sentry.io/xxxx');
  static ShakeDetector shakeDetector;

  factory BackgroundService() => _backgroundService;

  Future<void> start() async {
    if (await isRunning()) {
      return;
    }
    
    if (IsolateNameServer.lookupPortByName(_isolateName) != null) {
      IsolateNameServer.removePortNameMapping(_isolateName);
    }

    IsolateNameServer.registerPortWithName(port.sendPort, _isolateName);

    await _initPlatformState();

    await ensureAlwaysBackground ();

    _startSOSListener();

    await _startLocationService();
  }

  void stop() async {
    if (!await isRunning()) {
      return;
    }

    _stopSOSListener();

    if (IsolateNameServer.lookupPortByName(_isolateName) != null) {
      IsolateNameServer.removePortNameMapping(_isolateName);
    }

    BackgroundLocator.unRegisterLocationUpdate();
  }

  Future<bool> isRunning() =>
      BackgroundLocator.isRegisterLocationUpdate() /*_isRunning*/;

  void updateShakeThreshold() => _startShakeListener();

  static Future<void> _startSOSListener() async {
    _startShakeListener();
    _startPowerButtonListener();
  }

  static void _stopSOSListener() {
    _stopShakeListener();
    _stopPowerButtonListener();
  }

  static Future<void> _startShakeListener() async {
    if (shakeDetector != null) {
      _stopShakeListener();
    }

    try {
      shakeDetector = ShakeDetector.autoStart(
          shakeThresholdGravity: getShakeThresholdGravity(),
          onPhoneShake: () => sosHandler.run());
    } catch (error, stackTrace) {
      try {
        await _backgroundService.sentry.captureException(
          exception: error,
          stackTrace: stackTrace,
        );
      } catch (error) {
        print(error);
      }
    }
  }

  static void _startPowerButtonListener() {
  }

  static void
      _stopPowerButtonListener() => null;

  static void _stopShakeListener() => shakeDetector?.stopListening();

  Future<void> _startLocationService() =>
      BackgroundLocator.registerLocationUpdate(
        locationCallback,
        //optional
        initCallback: _initCallback,
        disposeCallback: _disposeCallback,
        androidNotificationCallback: _notificationCallback,
        settings: LocationSettings(
          //Scroll down to see the different options
          notificationMsg: "Tap to Open App",
          notificationIcon: '@drawable/ic_notification',
          notificationTitle: "TrackAm SOS Activated",
          notificationIconColor: Colors.redAccent,
          notificationChannelName: 'TrackAm SOS',
          wakeLockTime: 60,
          autoStop: false,
          interval: 1,
          distanceFilter: 1000,
          accuracy: LocationAccuracy.POWERSAVE,
        ),
      ).whenComplete(_disposeCallback);

  static void _initCallback(Map<String, dynamic> args) => _startSOSListener();

  static void _disposeCallback() => _stopSOSListener();

  static void locationCallback(LocationDto locationDto) {
    final SendPort send = IsolateNameServer.lookupPortByName(_isolateName);
    send?.send(locationDto);
  }

  static void _notificationCallback() {
    print('User clicked on the notification');
  }

  Future<void> _initPlatformState() => BackgroundLocator.initialize();
  
  BackgroundService._internal();
}

[uzenith360]

I later discovered the real issue was that the background locator callbacks need to be in the root of lib folder. I’m not sure that was pointed out anywhere in documentation.

Maybe it should be added as a note in documentation incase someone else faces this issue.

Ofcourse, i could do a pr

@mehdok @gpibarra

[mehdok]

It seems that the issue is solved, I’m closing the issue but feel free to open it anytime;