doctor_app_flutter/lib/screens/auth/login_screen.dart

import 'dart:async';

import 'package:doctor_app_flutter/widgets/auth/known_user_login.dart';
import 'package:flutter/material.dart';
import 'package:shared_preferences/shared_preferences.dart';

import '../../widgets/auth/auth_header.dart';
import '../../widgets/auth/login_form.dart';

class Loginsreen extends StatelessWidget {
  Future<SharedPreferences> _prefs = SharedPreferences.getInstance();
  int platformImei;
  Future<void> _incrementCounter() async {
    final SharedPreferences prefs = await _prefs;
    final int counter = (prefs.getInt('counter') ?? 0) + 1;
      platformImei = prefs.getInt('platformImei'); 
    // setState(() {
      print('platformImei'+platformImei.toString());
       prefs.setInt("counter", counter).then((bool success) {
        return counter;
      // });
    });
  }
  @override
  Widget build(BuildContext context) {

    // prefs.setInt("counter", 1);
    _incrementCounter();
    return Scaffold(
      backgroundColor: Colors.white,
      body: SingleChildScrollView(
        child: Container(
            margin: EdgeInsetsDirectional.fromSTEB(30, 0, 0, 0),
            alignment: Alignment.topLeft,
            child: Column(
                crossAxisAlignment: CrossAxisAlignment.start,
                children: <Widget>[
                  AuthHeader(),
                  platformImei == null?LoginForm():KnownUserLogin(),
                ])),
      ),
    );
  }
}