class crudMedthods{   getDataUser(Data) async {
     return await Firestore.instance.collection('users').document(Data).get();   } }

 class LoginScreen extends StatefulWidget {   @override
 _LoginScreenState createState() => _LoginScreenState(); }

 class _LoginScreenState extends State<LoginScreen> {
 TextEditingController username = TextEditingController();
 SharedPreferences sharedPreferences;   crudMedthods crudObj =
 crudMedthods();   var user;

   Future<void> signIn() async {
     final formState = _formKey.currentState;
     if (formState.validate()) {
       formState.save();
       await FirebaseAuth.instance.signInWithEmailAndPassword(
           email: username.text, password: password.text);
       try {
         Navigator.push(
             context, MaterialPageRoute(builder: (context) => HomeScreen()));
       } catch (e) {
         print(e.message);
       }
     }   }

   @override   Widget build(BuildContext context) {
     return MaterialApp(
       home: Scaffold(
         resizeToAvoidBottomPadding: false,
         body: ListView(children: <Widget>[
           Column(children: <Widget>[TextFormField(
             controller: username,
             decoration: InputDecoration(
               border: OutlineInputBorder(
                   borderSide: BorderSide(
                       color: Colors.lightBlue[50], width: 10),
                   borderRadius: BorderRadius.circular(26.0)),
               contentPadding: EdgeInsets.symmetric(vertical: 17.0, horizontal: 10.0),
               hintText: "username",
               fillColor: Colors.teal[200].withOpacity(0.3),
               filled: true,
               labelText: 'Email',
             ),
             keyboardType: TextInputType.emailAddress,
           ),
             RaisedButton(
               shape: RoundedRectangleBorder(
                   borderRadius: BorderRadius.circular(25.0),
                   side: BorderSide(
                       width: 1, color: Color(0xffd50000))),
               color: Color(0xffd50000),
               onPressed: () async {
                 crudObj.getDataUser(username.text).then((results) {
                   setState(() {
                     user = results;
                   });
                 });
                 signIn();
                 sharedPreferences =
                 await SharedPreferences.getInstance();
                 sharedPreferences.setString(
                     "username", username.text);
                 sharedPreferences.setBool(
                     "isAdmin", user["isAdmin"]);
               },
               child: Text(
                 'Sign in with Email',
                 style: TextStyle(
                   fontSize: 20,
                   color: Colors.white,
                 ),
               ),
             ),
           ])
         ]),
       ),
     );
} }