Flutter Flavors code

app_config.dart

import 'package:flutter/material.dart';
import 'package:flutter_flavors/repository/dog_repository.dart';

abstract class AppConfig {
  String get appName;
  DogRepository get dogRepository;
  ColorSwatch get colorSwatch;
}

app_config_dev.dart

import 'package:flutter/material.dart';
import 'package:flutter_flavors/config/app_config.dart';
import 'package:flutter_flavors/repository/dog_repository.dart';
import 'package:flutter_flavors/repository/dog_repository_dev.dart';

class AppConfigDev implements AppConfig {
  final _dogRepository = DogRepositoryDev();
  final _appName = "(DEV) Dog Match";

  @override
  String get appName => _appName;

  @override
  DogRepository get dogRepository => _dogRepository;

  @override
  ColorSwatch get colorSwatch => Colors.orange;
}

app_config_prod.dart

import 'package:flutter/material.dart';
import 'package:flutter_flavors/config/app_config.dart';
import 'package:flutter_flavors/repository/dog_repository.dart';
import 'package:flutter_flavors/repository/dog_repository_prod.dart';

class AppConfigProd implements AppConfig {
  final _dogRepository = DogRepositoryProd();
  final _appName = "Dog Match";

  @override
  String get appName => _appName;

  @override
  DogRepository get dogRepository => _dogRepository;

  @override
  ColorSwatch get colorSwatch => Colors.deepPurple;
}

dog_app.dart

import 'package:flutter/material.dart';
import 'package:flutter_flavors/config/app_config.dart';
import 'package:flutter_flavors/widgets/dog_stack.dart';
import 'package:flutter_flavors/widgets/generic_button.dart';
import 'package:flutter_flavors/widgets/generic_loading_spinner.dart';

class DogApp extends StatefulWidget {
  DogApp(this.appConfig);

  final AppConfig appConfig;

  @override
  _DogAppState createState() => _DogAppState(appConfig);
}

class _DogAppState extends State<DogApp> {
  _DogAppState(this.appConfig);

  final AppConfig appConfig;

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      theme: ThemeData(
        primarySwatch: appConfig.colorSwatch,
        backgroundColor: Theme.of(context).backgroundColor,
        visualDensity: VisualDensity.adaptivePlatformDensity,
      ),
      home: Scaffold(
        appBar: AppBar(
          title: Text(appConfig.appName),
          centerTitle: true,
        ),
        body: Stack(
          children: <Widget>[
            Center(
              child: GenericButton(
                child: Text('More dogs!'),
                onPressed: _refreshDogImages,
              ),
            ),
            Container(
              color: Theme.of(context).canvasColor,
              child: FutureBuilder(
                key: UniqueKey(),
                future: appConfig.dogRepository.getDogImages(count: 10),
                builder: (context, snapshot) {
                  final dogImages = snapshot.data as List<ImageProvider>;
                  if (snapshot.hasData) {
                    return DogStack(images: dogImages);
                  } else if (snapshot.hasError) {
                    return Center(child: Text('There is an error in dog server'));
                  } else {
                    return Center(
                      child: Container(child: GenericLoadingSpinner()),
                    );
                  }
                },
              ),
            ),
          ],
        ),
      ),
      debugShowCheckedModeBanner: false,
    );
  }

  void _refreshDogImages() {
    setState(() {});
  }
}

dog_repository.dart

import 'package:flutter/material.dart';

abstract class DogRepository {
  Future<List<ImageProvider>> getDogImages({int count});
}

dog_repository_dev.dart

import 'package:flutter/material.dart';
import 'package:flutter_flavors/repository/dog_repository.dart';

class DogRepositoryDev implements DogRepository {
  @override
  Future<List<ImageProvider>> getDogImages({int count = 1}) {
    return Future.value(List.generate(count, (_) => AssetImage('assets/dog.jpg')));
  }
}

dog_repository_prod.dart

import 'dart:convert';

import 'package:flutter/material.dart';
import 'package:flutter_flavors/repository/dog_repository.dart';
import 'package:http/http.dart' as http;

class DogRepositoryProd implements DogRepository {
  @override
  Future<List<ImageProvider>> getDogImages({int count = 1}) async {
    final response = await http.get('https://dog.ceo/api/breeds/image/random/$count');
    final List<ImageProvider> images =
        (json.decode(response.body)['message'] as List).map((dogUrl) => NetworkImage(dogUrl)).toList();

    return Future.value(images);
  }
}

launch.json

{
    "version": "0.2.0",
    "configurations": [
        {
            "name": "Dog Match Dev",
            "request": "launch",
            "type": "dart",
            "program": "lib/main_dev.dart",
        },
        {
            "name": "Dog Match Prod",
            "request": "launch",
            "type": "dart",
            "program": "lib/main_prod.dart",
        }
    ]
}

main_common.dart

import 'package:flutter/material.dart';
import 'package:flutter_flavors/config/app_config.dart';
import 'package:flutter_flavors/dog_app.dart';

void mainCommon(AppConfig appConfig) {
  runApp(DogApp(
    appConfig,
  ));
}

main_dev.dart

import 'package:flutter_flavors/config/app_config.dart';
import 'package:flutter_flavors/config/app_config_dev.dart';
import 'package:flutter_flavors/main_common.dart';

void main() {
  final AppConfig appConfig = AppConfigDev();
  mainCommon(appConfig);
}

main_prod.dart

import 'package:flutter_flavors/config/app_config.dart';
import 'package:flutter_flavors/config/app_config_prod.dart';
import 'package:flutter_flavors/main_common.dart';

void main() {
  final AppConfig appConfig = AppConfigProd();
  mainCommon(appConfig);
}