cfg--sample.dart

class Cfg {
  static final apiUrl = 'https://www.this-is-my-backend-api-site.com/api';
  static final urlAuth = apiUrl+'/auth';
}

home.dart

//import 'dart:async';
import 'package:flutter/rendering.dart';
//import 'package:provider/provider.dart';
import 'package:flutter/material.dart';
//import '../models/user.dart';
//import '../util/login_form_validator.dart';
import '../ui/bb_convex.dart';

class ScreenHome extends StatefulWidget {
  @override
  _ScreenHomeState createState() => _ScreenHomeState();
}

class _ScreenHomeState extends State<ScreenHome> {
  final formKey = GlobalKey<FormState>();
  final scaffoldKey = GlobalKey<ScaffoldState>();
  // var _context;

  Widget build(BuildContext context) {
    // _context = context;
    return Stack(children: [
      Container(
        decoration: new BoxDecoration(
          gradient: new LinearGradient(
              colors: [
                //const Color(0xFF3366FF),
                //const Color(0xFF00CCFF),
                const Color(0xFFc0CCFF),
                const Color(0xFF5366cF),
              ],
              begin: const FractionalOffset(0.0, 0.0),
              end: const FractionalOffset(1.2, .5),
              //begin: Alignment.topLeft,
              //end: Alignment(0.8, 0.0),
              stops: [0.0, 1.0],
              tileMode: TileMode.clamp),
        ),
      ),
      Scaffold(
        key: scaffoldKey,
        extendBodyBehindAppBar: false,
        //backgroundColor: Colors.white,
        backgroundColor: Colors.transparent,
        appBar: AppBar(
          title: Text(
            'Le\'App',
            style: TextStyle(color: Colors.white70),
          ),
          elevation: 0.0,
          backgroundColor: Colors.transparent,
          flexibleSpace: Container(
            decoration: new BoxDecoration(
              gradient: new LinearGradient(
                  colors: [
                    ////const Color(0xFF3366FF), const Color(0xFF00CCFF),
                    //const Color(0xf05346FF), const Color(0x005346FF),
                    const Color(0x20ffffff), const Color(0x00ffffff),
                  ],
                  begin: const FractionalOffset(.6, 1 - (-0.2)),
                  end: const FractionalOffset(1 - 0.475, 1 - 1.1),
                  stops: [0.0, 1.0],
                  tileMode: TileMode.clamp),
            ),
          ),
          automaticallyImplyLeading: false,
          leading: null,
          actions: <Widget>[
            new IconButton(
              icon: new Icon(Icons.account_circle),
              onPressed: () => Navigator.of(context).pop(null),
            ),
          ],
        ),
        body: Stack(
          children: [
            Padding(
              padding: const EdgeInsets.symmetric(horizontal: 16.0),
              child: SingleChildScrollView(
                  child: Center(child: Text("You are here"))),
            ),
          ],
        ),
        bottomNavigationBar: BBar(),
      )
    ]);
  }
}

http_session.dart

import 'package:flutter/cupertino.dart';
import 'package:flutter/rendering.dart';
import 'package:http/http.dart' as http;
import 'dart:convert';

class HttpSession extends ChangeNotifier {
  Map<String, String> headers = {};

  //HttpSession() => {};

  Future<Map> get(String url) async {
    http.Response response = await http.get(url, headers: headers);
    updateCookie(response);
    return json.decode(response.body);
  }

  Future<Map> post(String url, dynamic data) async {
    http.Response response = await http.post(url, body: data, headers: headers);
    updateCookie(response);
    return json.decode(response.body);
  }

  void updateCookie(http.Response response) {
    String rawCookie = response.headers['set-cookie'];
    if (rawCookie != null) {
      int index = rawCookie.indexOf(';');
      headers['cookie'] =
          (index == -1) ? rawCookie : rawCookie.substring(0, index);
    }
  }
}

/*
  static InheritedHttpSession of(BuildContext context) {
    return context.dependOnInheritedWidgetOfExactType<InheritedHttpSession>();
  }

  @override
  bool updateShouldNotify(HttpSession old) => session != old.session;}
  bool updateShouldNotify(HttpSession old) => session != old.session;}

class InheritedHttpSession extends InheritedWidget {
  HttpSession session = HttpSession();

  static InheritedHttpSession of(BuildContext context) {
    return context.dependOnInheritedWidgetOfExactType<InheritedHttpSession>();
  }

  @override
  bool updateShouldNotify(HttpSession session) => session != old.session;
}
*/

login.dart

//import 'dart:async';
import 'package:flutter/rendering.dart';
import 'package:provider/provider.dart';
import 'package:flutter/material.dart';
import '../models/user.dart';
import '../util/login_form_validator.dart';

class OffsiteUserChangeListener extends StatelessWidget {
  final scaffoldKey;
  final user;

  const OffsiteUserChangeListener({
    Key key,
    this.scaffoldKey,
    this.user,
  }) : super(key: key);

  @override
  Widget build(BuildContext context) {
    // Haven't tried logging in yet. Also, we might not even have build()'ed
    if (user.loginState == LoginState.loggedIn) {
      // We handled this ourselves. This is just a reminder for me
    } else if (user.loginState == LoginState.success) {
      user.loginState = LoginState.loggedIn;
      WidgetsBinding.instance.addPostFrameCallback((_) {
        Navigator.pushReplacementNamed(context, '/home');
      });
    } else if (user.loginState == LoginState.inProgress) {
      return Stack(children: [
        Positioned.fill(child: Container(color: Color.fromRGBO(255, 255, 255, .7))),
        //Opacity( opacity:1.0,
        Center(child: CircularProgressIndicator()),
      ]);
    } else if (user.loginState == LoginState.failed) {
      final snackbar = SnackBar(
        content: Text("Couldn't log in: ${user.loginMsg}"),
      );
      WidgetsBinding.instance.addPostFrameCallback((_) {
        Scaffold.of(context).showSnackBar(snackbar);
      });
    }
    return Offstage(child: Container(width:0, height:0)); // Dummy so we exist.
  }
}


class ScreenLogin extends StatefulWidget {
  @override
  _ScreenLoginState createState() => _ScreenLoginState();
}

class _ScreenLoginState extends State<ScreenLogin> {
  final formKey = GlobalKey<FormState>();
  final scaffoldKey = GlobalKey<ScaffoldState>();

  String _userid; // For the form fields.
  String _pw;
  var _context;

  void _submitCommand() {
    final form = formKey.currentState;
    var _user = Provider.of<User>(_context, listen:false);
    if (form.validate()) {
      form.save();  // userid & pw passed val rules and are in _userid & _pw fields
      _user.loginUnknownID(id: _userid, pw: _pw);   //_loginCommand();
    }
  }

  @override
  Widget build(BuildContext context) {
    _context = context;
    return Scaffold(
      key: scaffoldKey,
      backgroundColor: Colors.white,
      appBar: AppBar(
        title: Text('Login'),
      ),
      body:
        Stack(children: [
          Padding(
            padding: const EdgeInsets.symmetric(horizontal: 16.0),
            child: SingleChildScrollView(
              child: Form(
                key: formKey,
                child: Column(
                  children: <Widget>[
                    GestureDetector(
                      onTap: () { Navigator.pop(context); },
                      child: Hero(
                        tag: 'splash_img',
                        child: Image.asset('lib/assets/videos/0128.png', width: 150, height: 150,
                          ),
                      ),
                    ),
                    TextFormField(
                      initialValue: "Username",
                      decoration: InputDecoration(labelText: 'Username / Email'),
                      validator: (val) => !ValidatorUsernameOrEmail.validate(val) ? 'Invalid Username or Email.' : null,
                      onSaved: (val) => _userid = val,
                    ),
                    TextFormField(
                      initialValue: "Password",
                      decoration: InputDecoration(labelText: 'Password'),
                      validator: (val) => val.length < 4 ? 'Password too short..' : null,
                      onSaved: (val) => _pw = val,
                      obscureText: true,
                    ),
                    RaisedButton(
                      onPressed: _submitCommand,
                      child: Text('Sign in'),
                    ),
                  ],
                ),
              ),
            ),
        ),
        Consumer<User>(
          builder: (context, user, child) => OffsiteUserChangeListener(
            scaffoldKey: scaffoldKey,
            user: user,
          ),
        ),
      ],)
    );
  }
}

main.dart

import 'package:flutter/foundation.dart';
import 'package:provider/provider.dart';
import 'package:flutter/material.dart';
import 'models/user.dart';
import 'screens/splash.dart';
import 'screens/login.dart';
import 'screens/home.dart';
import 'util/http_session.dart';
void main() => runApp(AppMain());

class Session extends InheritedWidget {
  final HttpSession httpSession = HttpSession();

  Session(child): super(child: child);

  @override
  bool updateShouldNotify(Session old) =>
    httpSession != old.httpSession;
}

class AppMain extends StatefulWidget {
  AppMain({Key key}) : super(key: key);

  @override
  _AppMainState createState() => _AppMainState();
}

class _AppMainState extends State<AppMain> {
  @override
  void initState() {
    super.initState();
  }
 
  @override
  Widget build(BuildContext context) {
    return ChangeNotifierProvider(
      create: (context) => User(),
    //return MultiProvider(
     // providers: [
      //  Provider<User>(create: (_) => User()),
       // Provider<HttpSession>(create: (_) => HttpSession()),
      //],
      child: Session(MaterialApp(
        title: 'Named Routes Demo',
        initialRoute: '/',
        routes: {
          '/': (context) => ScreenSplash(),
          '/login': (context) => ScreenLogin(),
          '/home': (context) => ScreenHome(),
        },
      )),
    );
  }
}

splash.dart

import 'package:video_player/video_player.dart';
import 'package:flutter/material.dart';
import 'package:flutter/foundation.dart' show kIsWeb;
import '../util/common.dart';

class ScreenSplash extends StatefulWidget {
  @override
  _ScreenSplashState createState() => _ScreenSplashState();
}

class _ScreenSplashState extends State<ScreenSplash> {
  VideoPlayerController _controller;
  Future<void> _initializeVideoPlayerFuture;
  ScreenState _screenState = ScreenState.here;
  // bool _haveLeftScreen = false;
  //bool _userHasInteracted = false; // used for web video, so we get an interaction
                                   // in and then can play audio.

  @override
  void initState() {
    super.initState();
    _controller = VideoPlayerController.asset(
      'lib/assets/videos/vid.mp4',
    );
    _initializeVideoPlayerFuture = _controller.initialize();
    super.initState();
    if (kIsWeb) _controller.setVolume(0.0); // needed for autovideo play
    _controller.play();
    _controller.addListener(() async {
      if (!_controller.value.isPlaying) {
        if (_screenState != ScreenState.here) {
          //_controller.dispose();
        } else {
          //_haveLeftScreen = true;
          _screenState = ScreenState.left;
          await Navigator.pushNamed(context, '/login');
          _screenState = ScreenState.returned;
          //_haveLeftScreen = false;
          _controller.setVolume(1.0);
        }
      }
    });

    /* ..setVolume(1.0)..initialize()..play();
      .then((_) {
        // Ensure the first frame is shown after the
        // video is initialized, even before the
        //  play button has been pressed.
        setState(() {});
      }); */
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      drawer: Drawer(),
      backgroundColor: Colors.white,
      appBar: AppBar(
        title: Text('Veedios'),
        backgroundColor: Colors.black87,
      ),
      body: Column(
          mainAxisAlignment: MainAxisAlignment.center,
          crossAxisAlignment: CrossAxisAlignment.center,
          children: [
            FutureBuilder(
                future: _initializeVideoPlayerFuture,
                builder: (context, snapshot) {
                  if (snapshot.connectionState == ConnectionState.done) {
                    return AspectRatio(
                        aspectRatio: _controller.value.aspectRatio,
                        child: GestureDetector(
                          behavior: HitTestBehavior.opaque,
                          onTap: () async {
                            //_userHasInteracted = true;
                            _controller.setVolume(1.0);
                            if (!_controller.value.isPlaying) {
                              _controller.seekTo(Duration(seconds: 0));
                              _controller.play();
                            } else {
                              //_controller.pause();
                              //_haveLeftScreen = true;
                              _screenState = ScreenState.left;
                              await Navigator.pushNamed(context, '/login');
                              _screenState = ScreenState.returned;
                              //_haveLeftScreen = false;
                            }
                          },
                          child: IgnorePointer(
                              ignoring: true,
                              child: Stack(children: <Widget>[
                                // Image.asset(
                                //   'lib/assets/video/0019.png',
                                //   width: 100,
                                //   height: 100,
                                //   ),

                                Padding(
                                  padding: const EdgeInsets.all(72.0),
                                  child: Hero(
                                    tag: 'splash_img',
                                    //child: Image.asset('lib/assets/videos/0128.png',),
                                    child: VideoPlayer(_controller),
                                  ),
                                ),
                                /* Hero(
                          tag: 'splash_img',
                          child: Image.asset('lib/assets/video/vid.png'),
                        ), */
                              ])),
                        ));
                  } else {
                    return Center(child: CircularProgressIndicator());
                  }
                })
          ]),
      /*
        floatingActionButton: FloatingActionButton(
          onPressed: () {
            setState(() {
              _controller.value.isPlaying
                  ? _controller.pause()
                  : _controller.play();
            });
          },
          child: Icon(
            _controller.value.isPlaying ? Icons.pause : Icons.play_arrow,
          ),
        ),
        */
    );
  }

  @override
  void dispose() {
    _controller.dispose();
    super.dispose();
  }
}

user.dart

import 'package:flutter/foundation.dart';
import '../util/cfg.dart';
import 'package:http/http.dart' as http;
import 'dart:async';
import 'dart:convert';
import '../util/http_session.dart';
import 'package:provider/provider.dart';
//import 'dart:io';

enum LoginState {
  pre,
  inProgress,
  failed,
  success,         // when login succeeds
  loggedIn,        // callers of sign in should set this themselves
                   //  once they've detected the success.
}

class User extends ChangeNotifier {
  String id;
  String username;
  String pw;
  String token;
  LoginState loginState = LoginState.pre;
  String loginMsg;
  LoginResponse loginResponse;

  void loginUnknownID({  // Not sure if username or email yet...
      @required id,
      @required pw,
      }) async {
    assert(id != null && pw != null,
      'We need a username or email and a password.');
    this.id = id;        // No login yet. Just pretend
    this.pw = pw;
    loginState = LoginState.inProgress;
    notifyListeners();   // But pretend slowly \/  \/  \/
    loginResponse = await userGetLoginResponse(id: id, pw: pw);
    if (loginResponse.success == 1) {
      this.username = loginResponse.username;
      this.token = loginResponse.token;
      this.loginState = LoginState.success;
      this.pw = null;
    } else {
      this.loginMsg = loginResponse.msg ?? "Unknown login error";
      this.loginState = LoginState.failed;
    }
    //await Future.delayed(const Duration(seconds: 2), () {});
    notifyListeners();
  }
}

Future<LoginResponse> userGetLoginResponse({id, pw}) async {
  LoginResponse loginResponse;

  var http = Provider.of<HttpSession>(_context, listen:false);

  final response = await http.get(
    Cfg.urlAuth,
    headers: {
      'Authorization': "Basic $id:$pw"
      //HttpHeaders.authorizationHeader: "$id:$pw"
    },
  );
  if (response.statusCode == 200) {
    final responseJson = json.decode(response.body);
    loginResponse = LoginResponse.fromJsonIsSuccess(responseJson);
  } else {
    loginResponse = LoginResponse.bad(404);
  }
  return loginResponse;
}

class LoginResponse {
  final String username;
  final String token;
  final String msg;
  final int success;
  final int statusCode;
  LoginResponse({this.username, this.token,
    this.success, this.msg, this.statusCode});
  factory LoginResponse.fromJsonIsSuccess(Map<String, dynamic> json) {
    if (json.containsKey('username') &&
        json.containsKey('token') &&
        json.containsKey('success')) {
      return LoginResponse(
        username: json['username'],
        token: json['token'],
        success: json['success'],
        msg: json['msg'] ?? "",
        statusCode: 200,
      );
    } else {
      return LoginResponse(
        username: "",
        token: "",
        success: 0,
        msg: json['msg'] ?? "Unknown error. We're sorry too.",
        statusCode: 200,
      );
    }
  }
  factory LoginResponse.bad(int code) {
    return LoginResponse(
      username: "",
      token: "",
      success: 0,
      msg: "HTTP error ($code)",
      statusCode: code,
    );
  }
}