basic signup demo flutter

import 'dart:convert';

import 'package:flutter/material.dart';
import 'package:http/http.dart' as http;

import 'SignUpResponseModel.dart';

class SignUpPage extends StatefulWidget {
  @override
  _SignUpPageState createState() => _SignUpPageState();
}

class _SignUpPageState extends State<SignUpPage> {
  final _formKey = GlobalKey<FormState>();
  final GlobalKey<ScaffoldState> _scaffoldKey = new GlobalKey<ScaffoldState>();
  String _name, _email, _password, _phone;
  bool _autoValidate = false;
  bool _isSubmitting = false;
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      key: _scaffoldKey,
      appBar: AppBar(
        elevation: 0.0,
        title: Text("SIGNUP"),
        centerTitle: true,
      ),
      body: SingleChildScrollView(
        child: Form(
          autovalidate: _autoValidate,
          key: _formKey,
          child: Container(
            padding: EdgeInsets.only(left: 15, right: 15, top: 15),
            child: Column(children: [
              Text(
                "SIGNUP",
                style: TextStyle(fontSize: 30),
              ),
              SizedBox(height: 10),
              TextFormField(
                  validator: (value) =>
                      value.trim().length < 1 ? "Enter a value" : null,
                  onSaved: (value) => _name = value,
                  decoration: InputDecoration(
                      border: OutlineInputBorder(
                        borderRadius: BorderRadius.circular(10.0),
                      ),
                      hintText: "NAME")),
              SizedBox(height: 10),
              TextFormField(
                  validator: (value) =>
                      value.trim().length < 1 ? "Enter a value" : null,
                  onSaved: (value) => _email = value,
                  decoration: InputDecoration(
                      border: OutlineInputBorder(
                        borderRadius: BorderRadius.circular(10.0),
                      ),
                      hintText: "Email")),
              SizedBox(height: 10),
              TextFormField(
                  validator: (value) =>
                      value.trim().length < 1 ? "Enter a value" : null,
                  onSaved: (value) => _phone = value,
                  decoration: InputDecoration(
                      border: OutlineInputBorder(
                        borderRadius: BorderRadius.circular(10.0),
                      ),
                      hintText: "PHONE")),
              SizedBox(height: 10),
              TextFormField(
                  validator: (value) =>
                      value.trim().length < 1 ? "Enter a value" : null,
                  onSaved: (value) => _password = value,
                  decoration: InputDecoration(
                      border: OutlineInputBorder(
                        borderRadius: BorderRadius.circular(10.0),
                      ),
                      hintText: "Password")),
              SizedBox(height: 20),
              _isSubmitting
                  ? CircularProgressIndicator()
                  : RaisedButton(
                      onPressed: () => _signUpUser(context),
                      child: Text("SIGNUP"),
                    )
            ]),
          ),
        ),
      ),
    );
  }

  void _signUpUser(BuildContext context) {
    if (_formKey.currentState.validate()) {
      _formKey.currentState.save();

      setState(() {
        _isSubmitting = true;
      });

      Map<String, String> _payload = Map();
      _payload["name"] = _name;
      _payload["email"] = _email;
      _payload["password"] = _password;
      _payload["phone"] = _phone;

      print(_payload.toString());

      http
          .post("https://moving-kinshasa.herokuapp.com/users/new",
              headers: {"Content-Type": "application/json"},
              body: json.encode(_payload))
          .then((response) {
        setState(() {
          _isSubmitting = false;
        });

        //serialize json to Dart
        SignUpResponse signUpResponse =
            SignUpResponse.fromJson(json.decode(response.body));

        if (response.statusCode == 200) {
          if (signUpResponse.message == "success") {
            //navigate to another screen
            _showSnackBar("Welcome");
          } else {
            _showSnackBar(signUpResponse.message);
          }
        } else {
          _showSnackBar(signUpResponse.message);
        }
      }).catchError((onError) {
        setState(() {
          _isSubmitting = false;
        });
      });
    } else {
      setState(() {
        _autoValidate = true;
      });
    }
  }

  void _showSnackBar(message) {
    _scaffoldKey.currentState.showSnackBar(
      SnackBar(
        content: Text(message),
      ),
    );
  }
}



//user signup response model



class SignUpResponse {
  String message;
  Response response;

  SignUpResponse({this.message, this.response});

  SignUpResponse.fromJson(Map<String, dynamic> json) {
    message = json['message'];
    response = json['response'] != null
        ? new Response.fromJson(json['response'])
        : null;
  }

  Map<String, dynamic> toJson() {
    final Map<String, dynamic> data = new Map<String, dynamic>();
    data['message'] = this.message;
    if (this.response != null) {
      data['response'] = this.response.toJson();
    }
    return data;
  }
}

class Response {
  String sId;
  int iV;

  Response({this.sId, this.iV});

  Response.fromJson(Map<String, dynamic> json) {
    sId = json['_id'];
    iV = json['__v'];
  }

  Map<String, dynamic> toJson() {
    final Map<String, dynamic> data = new Map<String, dynamic>();
    data['_id'] = this.sId;
    data['__v'] = this.iV;
    return data;
  }
}