GetXService

main.dart

import 'package:flutter/material.dart';
import 'package:flutter_getx/service.dart';
import 'package:get/get.dart';

Future<void> main() async {
  await initServices();
  runApp(MyApp());
}

Future<void> initServices() async {
  print('starting services ...');
  await Get.putAsync<Service>(() async => await Service());
  print('All services started...');
}

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    // TODO: implement build
    return GetMaterialApp(
      title: "GetX Service",
      home: Scaffold(
        appBar: AppBar(title: Text("GetX Service")),
        body: Center(
          child: Column(
            mainAxisAlignment: MainAxisAlignment.center,
            crossAxisAlignment: CrossAxisAlignment.center,
            children: [
              RaisedButton(
                child: Text("Increment"),
                onPressed: () {
                  Get.find<Service>().incrementCounter();
                },
              ),
            ],
          ),
        ),
      ),
    );
  }
}

service.dart

import 'package:get/get.dart';
import 'package:shared_preferences/shared_preferences.dart';

//This class is like a GetxController.
// It shares the same lifecycle ( onInit(), onReady(), onClose()).
//It just notifies GetX Dependency Injection system,
// that this subclass can not be removed from memory.
class Service extends GetxService {

  Future<void> incrementCounter() async {
    SharedPreferences prefs = await SharedPreferences.getInstance();
    int counter = (prefs.getInt('counter') ?? 0) + 1;
    print('Pressed $counter times.');
    await prefs.setInt('counter', counter);
  }
}