My source code

import 'package:flutter/material.dart';
import 'package:wedding_app/models/constants/colors.dart';
import 'package:wedding_app/models/state/guest_list/guest_widget.dart';

class GuestPage extends GuestState {
  String name;
  TextEditingController _editingController = TextEditingController();

  // Create a global key that will uniquely identify the Form widget and allow
  // us to validate the form
  //
  // Note: This is a `GlobalKey<FormState>`, not a GlobalKey<MyCustomFormState>!
  final _formKey = GlobalKey<FormState>();

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

  @override
  Widget build(BuildContext context) {
    double textboxSize = MediaQuery.of(context).size.height / 1.6;

    return Form(
        key: _formKey,
        child: Scaffold(
            body: Builder(
                builder: (context) => Container(
                    height: textboxSize * 10,
                    child: Container(
                      padding: EdgeInsets.all(30),
                      child: Column(
                        crossAxisAlignment: CrossAxisAlignment.center,
                        children: buildForm(context),
                      ),
                    ))))); // How do I prevent these??
  }

  List<Widget> buildForm(BuildContext context) {
    return <Widget>[
      Column(
        crossAxisAlignment: CrossAxisAlignment.start,
        children: <Widget>[
          Container(
              child: Padding(
                  padding: EdgeInsets.only(bottom: 2),
                  child: Text(
                    "First Name",
                    style: TextStyle(fontFamily: "acme", fontSize: 20),
                  ))), // How do I prevent these??
          TextFormField(
            textAlign: TextAlign.left,
            maxLength: 40,
            style: TextStyle(height: 2, fontSize: 15, color: Colors.black87),
            controller: _editingController,
            validator: (value) {
              if (value.isEmpty) {
                return "Please enter a first name";
              }

              name = value;
            },
          )
        ],
      ),
      Column(
        crossAxisAlignment: CrossAxisAlignment.start,
        children: <Widget>[
          Container(
            child: Text(
              "Last Name",
              style: TextStyle(fontFamily: "acme", fontSize: 20),
            ),
          ),
          TextFormField(
            maxLength: 40,
            textAlign: TextAlign.start,
            style: TextStyle(height: 2, fontSize: 15, color: Colors.black87),
          )
        ],
      ),
      Padding(
          padding: EdgeInsets.only(top: 15.0),
          child: ButtonTheme(
              minWidth: 200,
              height: 50,
              child: new RaisedButton(
                color: ApplicationColors.black,
                textColor: ApplicationColors.ivory,
                shape: RoundedRectangleBorder(
                    borderRadius: BorderRadius.circular(30.0)),
                onPressed: () {
                  if (_formKey.currentState.validate()) {
                    _showToast(context, "valid");
                  }
                },
                child: Text("Submit",
                    style: new TextStyle(
                        color: ApplicationColors.ivory,
                        fontFamily: 'Acme',
                        fontSize: 20)), // How do I prevent these??
              ))) // How do I prevent these??
    ];
  }

  void _showToast(BuildContext context, String text) {
    final scaffold = Scaffold.of(context);
    scaffold.showSnackBar(
      SnackBar(
        content: Text(text),
        action: SnackBarAction(
            label: 'UNDO', onPressed: scaffold.hideCurrentSnackBar),
      ),
    );
  }
}