mobile-flutter/covas_mobile/lib/main.dart

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

import 'package:http/http.dart' as http;
import 'dart:convert';
import 'dart:io';

void main() {
  runApp(MyApp());
}

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      debugShowCheckedModeBanner: false,
      home: LoginDemo(),
    );
  }
}

class LoginDemo extends StatefulWidget {
  @override
  _LoginDemoState createState() => _LoginDemoState();
}

class _LoginDemoState extends State<LoginDemo> {
  TextEditingController inputPseudo = TextEditingController();
  TextEditingController inputPassword = TextEditingController();
  Future<void> _login(BuildContext context) async {
    var url = Uri.parse("http://localhost:8083/api/token");
    var pseudo = inputPseudo.text;
    var password = inputPassword.text;
    if ((pseudo.isNotEmpty) && (password.isNotEmpty)) {
      String credentials = "${pseudo}:${password}";
      Codec<String, String> stringToBase64 = utf8.fuse(base64);
      String encoded = stringToBase64.encode(credentials);
      var response = await http.get(url, headers: {
        HttpHeaders.authorizationHeader: 'Basic $encoded',
      });

      if ((response.statusCode == 200) || (response.statusCode == 201)) {
        Navigator.push(
            context,
            MaterialPageRoute(
                builder: (_) => MyHomePage(title: 'Flutter Demo')));
      } else {
        showErrorDialog(context, "Probleme d'authentification");
      }
    } else {
      showErrorDialog(context, "Champ vide");
    }
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      backgroundColor: Colors.white,
      appBar: AppBar(
        title: Text("Login Page"),
      ),
      body: SingleChildScrollView(
        child: Column(
          children: <Widget>[
            Padding(
              padding: const EdgeInsets.only(top: 60.0),
              child: Center(
                child: Container(
                    width: 200,
                    height: 150,
                    /*decoration: BoxDecoration(
                        color: Colors.red,
                        borderRadius: BorderRadius.circular(50.0)),*/
                    child: Image.asset('asset/images/flutter-logo.png')),
              ),
            ),
            Padding(
              //padding: const EdgeInsets.only(left:15.0,right: 15.0,top:0,bottom: 0),
              padding: EdgeInsets.symmetric(horizontal: 15),
              child: TextField(
                controller: inputPseudo,
                decoration: InputDecoration(
                    border: OutlineInputBorder(),
                    labelText: 'Email',
                    hintText: 'Enter valid email id as abc@gmail.com'),
              ),
            ),
            Padding(
              padding: const EdgeInsets.only(
                  left: 15.0, right: 15.0, top: 15, bottom: 0),
              //padding: EdgeInsets.symmetric(horizontal: 15),
              child: TextField(
                controller: inputPassword,
                obscureText: true,
                decoration: InputDecoration(
                    border: OutlineInputBorder(),
                    labelText: 'Password',
                    hintText: 'Enter secure password'),
              ),
            ),
            FlatButton(
              onPressed: () {
                //TODO FORGOT PASSWORD SCREEN GOES HERE
              },
              child: Text(
                'Forgot Password',
                style: TextStyle(color: Colors.blue, fontSize: 15),
              ),
            ),
            Container(
              height: 50,
              width: 250,
              decoration: BoxDecoration(
                  color: Colors.blue, borderRadius: BorderRadius.circular(20)),
              child: FlatButton(
                onPressed: () {
                  _login(context);
                },
                child: Text(
                  'Login',
                  style: TextStyle(color: Colors.white, fontSize: 25),
                ),
              ),
            ),
            SizedBox(
              height: 130,
            ),
            Text('New User? Create Account')
          ],
        ),
      ),
    );
  }

  showErrorDialog(BuildContext context, String text) {
    // Create AlertDialog
    AlertDialog dialog = AlertDialog(
      title: Text("Error"),
      content: Text(text),
      actions: [
        ElevatedButton(
            child: Text("OK"),
            style: ElevatedButton.styleFrom(
                primary: Colors.red,
                padding: EdgeInsets.symmetric(horizontal: 50, vertical: 20),
                textStyle:
                    TextStyle(fontSize: 15, fontWeight: FontWeight.normal)),
            onPressed: () {
              Navigator.of(context).pop("Yes, Of course!"); // Return value
            }),
      ],
    );

    // Call showDialog function to show dialog.
    Future futureValue = showDialog(
        context: context,
        builder: (BuildContext context) {
          return dialog;
        });
  }
}