final FirebaseAuth _firebaseAuth=FirebaseAuth.instance;
  void loginAndAuthenticateUser(BuildContext context)async
  {
    final User firebaseUser = (await _firebaseAuth
        .createUserWithEmailAndPassword(
        email: emailTextEditingController.text,
        password: passwordTextEditingController.text
    ).catchError((errMsg){
      displayToastMessage("Error: "+errMsg.toString(), context);
    })).user;
    if (firebaseUser!=null)
    {
       usersRef.child(firebaseUser.uid).once().then( (DataSnapshot snap){
        if(snap.value !=null){
          Navigator.pushNamedAndRemoveUntil(context, MainScreen.idScreen, (route) => false);
          displayToastMessage("You are logged-in now", context);
        }
        else
          {
            _firebaseAuth.signOut();
            displayToastMessage("No record exists for this user. Please create new account", context);
          }
      });
    }
    else
    {
      // error occured - display error msg
      displayToastMessage("Error Occurred, can not Sign  ", context);
    }

  }
}