jtlapp

export class MainApi1 {

  methodA(arg1: string, arg2: number): Promise<void> {
    // code for methodA
  }
    
  methodB(): Promise<number> {
    // code for methodB
  }
}

jtlapp

import 'package:flutter/material.dart';
import 'package:provider/provider.dart';

void main() => runApp(MyApp());

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return ChangeNotifierProvider<Counter>( // <=== PROVIDER
      builder: (context) => Counter(),

jtlapp

import 'package:flutter/material.dart';
import 'package:provider/provider.dart';

void main() => runApp(MyApp());

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return ChangeNotifierProvider<Counter>( // <=== PROVIDER
      builder: (context) => Counter(),

jtlapp

import 'dart:async';
import 'package:flutter/material.dart';
import 'package:provider/provider.dart';

void main() => runApp(MyApp());

class CountDown extends ValueNotifier<int> {
  CountDown(int downFrom) : super(downFrom) {
    scheduleDecrement();
  }

jtlapp

import 'package:flutter/material.dart';
import 'package:provider/provider.dart';

void main() => runApp(MyApp());

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',

jtlapp

import 'dart:async';
import 'package:flutter/material.dart';
import 'package:provider/provider.dart';

void main() => runApp(MyApp());

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    const appTitle = 'StreamProvider Demo';

jtlapp

import 'dart:async';
import 'package:flutter/material.dart';
import 'package:provider/provider.dart';

void main() => runApp(MyApp());

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    const appTitle = 'FutureProvider Demo';

jtlapp

import 'package:flutter/material.dart';

void main() => runApp(MyApp());

class MyApp extends StatelessWidget {
  // This widget is the root of your application.
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',

jtlapp

import 'package:flutter/material.dart';
import 'package:provider/provider.dart';

void main() => runApp(MyApp());

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',

jtlapp

import 'package:flutter/material.dart';

void main() => runApp(MyApp());

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      home: MyHomePage(),