The getter 'storeNumber' was called on null (Receiver: null) - dart

Question

I am trying to pass data from one screen to another, but I keep getting a null exception. Whenever I fill in the form on the first screen and proceed to next screen, I get a `
NoSuchMethodError: The getter 'storeNumber' was called on null
`
My variables class is ==> This entity class has variables that I populate using a form in the following class:
class StoreData {
String _storeNumber;
String _repName;
String _repCell;
DateTime _transactionDate = new DateTime.now();
StoreData(
this._storeNumber, this._repName, this._repCell, this._transactionDate);
String get storeNumber => _storeNumber;
set storeNumber(String value) {
_storeNumber = value;
}
String get repName => _repName;
DateTime get transactionDate => _transactionDate;
set transactionDate(DateTime value) {
_transactionDate = value;
}
String get repCell => _repCell;
set repCell(String value) {
_repCell = value;
}
set repName(String value) {
_repName = value;
}
}
The main class (in this case this is the first screen that sends data to second screen) includes the following code:
This class has a form that takes in 3 inputs and send them to second screen.
import 'package:cloud_firestore/cloud_firestore.dart';
import 'package:flutter/material.dart';
import 'FeedBack.dart';
import 'StoreData.dart';
void main() {
runApp(MaterialApp(
title: 'Navigation Basics',
home: FirstScreen(),
));
}
//get our entity class
StoreData storeDate;
// get variables from entity class
String storeNumber = storeDate.storeNumber;
String repName = storeDate.repName;
String repCell = storeDate.repCell;
DateTime transactionDate = storeDate.transactionDate;
class FirstScreen extends StatefulWidget {
#override
_FirstScreenState createState() => _FirstScreenState();
}
class _FirstScreenState extends State<FirstScreen> {
GlobalKey<FormState> _key = GlobalKey();
bool _validate = false;
_sendData() {
Navigator.push(
context,
MaterialPageRoute(
builder: (context) => FeedBack(
storeData: new StoreData(
storeNumber, repName, repCell, transactionDate))),
);
}
#override
Widget build(BuildContext context) {
return MaterialApp(
home: new Scaffold(
appBar: new AppBar(
title: new Text('Test App'),
),
body: new SingleChildScrollView(
child: new Container(
margin: new EdgeInsets.all(15.0),
child: new Form(
key: _key,
autovalidate: _validate,
child: formUI(),
),
),
),
),
);
}
Widget formUI() {
return new Column(
children: <Widget>[
new TextFormField(
decoration: new InputDecoration(hintText: 'Store Number'),
keyboardType: TextInputType.number,
validator: validateRepCell,
onSaved: (String val) {
storeNumber = val;
}),
new TextFormField(
decoration: new InputDecoration(hintText: 'Rep Full Name'),
validator: validateRepName,
onSaved: (String val) {
repName = val;
}),
new TextFormField(
decoration: new InputDecoration(hintText: 'Rep Phone Number'),
keyboardType: TextInputType.number,
validator: validateRepCell,
onSaved: (String val) {
repCell = val;
}),
new SizedBox(height: 15.0),
new RaisedButton(
onPressed: _sendData,
child: new Text('Proceed'),
)
],
);
}
// Validate Fields
String validateRepCell(String value) {
// String patttern = r'(^[a-zA-Z ]*$)';
RegExp regExp = new RegExp(r'^[+-]?([0-9]+([.][0-9]*)?|[.][0-9]+)$');
if (value.length == 0) {
return "Store Number is Required";
} else if (!regExp.hasMatch(value)) {
return "Store Number must be only have numbers";
}
return null;
}
String validateRepName(String value) {
String patttern = r'(^[a-zA-Z ]*$)';
RegExp regExp = new RegExp(patttern);
if (value.length == 0) {
return "Rep Name is Required";
} else if (!regExp.hasMatch(value)) {
return "Name must be a-z and A-Z";
}
return null;
}
}
The second screen's code is here:
class FeedBack extends StatelessWidget {
final StoreData storeData;
FeedBack({Key key, #required this.storeData}) : super(key: key);
#override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
title: Text("FeedBack Screen"),
),
body: new Container(
child: new Column(
children: <Widget>[
new RaisedButton(
onPressed: _sendToDatabase,
child: new Text('Press Me'),
),
new Text("${storeData.storeNumber}"),
],
),
),
);
}
_sendToDatabase() {
Firestore.instance.runTransaction((Transaction transaction) async {
CollectionReference reference = Firestore.instance.collection('Stores');
await reference.add({"test": "test", "testII": "test"});
});
}
}
I have been trying to solve this problem for a week now, but given my new experience with Dart and Flutter framework, it has been tough !
Any help would be appreciated,

Answer 1

You can use the following approach.
Remove the following lines from your code:
//get our entity class
StoreData storeDate;
As initially there will be no instance of StoreData available right now.
Now, declare new variables like the following:
String storeNumber;
String repName;
String repCell;
DateTime transactionDate;
And then assign the form values to them in onSaved method.
So when your form will be submitted, these values will be used for creating new StoreData and it will be passed to the Second page.
Here is the code for your main.dart file:
import 'package:flutter/material.dart';
import 'FeedBack.dart';
import 'StoreData.dart';
void main() {
runApp(MaterialApp(
title: 'Navigation Basics',
home: FirstScreen(),
));
}
// get variables from entity class
String storeNumber;
String repName;
String repCell;
DateTime transactionDate = DateTime.now();
class FirstScreen extends StatefulWidget {
#override
_FirstScreenState createState() => _FirstScreenState();
}
class _FirstScreenState extends State<FirstScreen> {
GlobalKey<FormState> _key = GlobalKey();
bool _validate = false;
_sendData() {
_key.currentState.save();
Navigator.push(
context,
MaterialPageRoute(
builder: (context) => FeedBack(
storeData: StoreData(
storeNumber, repName, repCell, transactionDate))),
);
}
#override
Widget build(BuildContext context) {
return MaterialApp(
home: new Scaffold(
appBar: new AppBar(
title: new Text('Test App'),
),
body: new SingleChildScrollView(
child: new Container(
margin: new EdgeInsets.all(15.0),
child: new Form(
key: _key,
autovalidate: _validate,
child: formUI(),
),
),
),
),
);
}
Widget formUI() {
return new Column(
children: <Widget>[
new TextFormField(
decoration: new InputDecoration(hintText: 'Store Number'),
keyboardType: TextInputType.number,
validator: validateRepCell,
onSaved: (String val) {
storeNumber = val;
}),
new TextFormField(
decoration: new InputDecoration(hintText: 'Rep Full Name'),
validator: validateRepName,
onSaved: (String val) {
repName = val;
}),
new TextFormField(
decoration: new InputDecoration(hintText: 'Rep Phone Number'),
keyboardType: TextInputType.number,
validator: validateRepCell,
onSaved: (String val) {
repCell = val;
}),
new SizedBox(height: 15.0),
new RaisedButton(
onPressed: _sendData,
child: new Text('Proceed'),
)
],
);
}
// Validate Fields
String validateRepCell(String value) {
// String patttern = r'(^[a-zA-Z ]*$)';
RegExp regExp = new RegExp(r'^[+-]?([0-9]+([.][0-9]*)?|[.][0-9]+)$');
if (value.length == 0) {
return "Store Number is Required";
} else if (!regExp.hasMatch(value)) {
return "Store Number must be only have numbers";
}
return null;
}
String validateRepName(String value) {
String patttern = r'(^[a-zA-Z ]*$)';
RegExp regExp = new RegExp(patttern);
if (value.length == 0) {
return "Rep Name is Required";
} else if (!regExp.hasMatch(value)) {
return "Name must be a-z and A-Z";
}
return null;
}
}