Cannot get proper value in validator in flutter - validation

Question

Steps to Reproduce
Here is the dartpad link go to it.
Enter any values to the Fields calculate the answer.
Add 0. to the start any Field
Expected results: validator should return 0.xyz
Actual results: validator returns 0xyz
Work around found: using onSaved solves this
Can anyone tell me why is it happening or is it bug in flutter then I will a new issue in the flutter repo
I'm printing the value coming from validator and in onChanged parsing string value to int.

Answer 1

Edit
when input 23 and then inert 0. , this line amount = int.parse(val); execute and stop and then click calculate button, so amount is 23 and value's runtimeType is String 023
TextFormField(
keyboardType: TextInputType.number,
validator: (value) {
print("amount $amount");
print(" ${value.runtimeType}");
print("validator amount value $value ");
if (value.isEmpty) {
return "Enter some amount";
} else if (double.parse(value).toInt() <= 0) {
return "Amount should be greater than 0";
}
return null;
},
onChanged: (val){
print("val1 $val");
amount = int.parse(val);
print("amount $amount");
}
You can copy paste run full code below
The reason why validator not return 0.xyz
Because onChanged executed before validator
So validator receive truncated value by int.parse(value)
If you remove amount = int.parse(value); validator will get correct value but
this condition if (int.parse(value) <= 0) will get Invalid radix-10 number
You need to change to if (double.parse(value).toInt() <= 0)
working demo
full code
import 'package:flutter/material.dart';
void main() {
runApp(MyApp());
}
class MyApp extends StatelessWidget {
#override
Widget build(BuildContext context) {
return MaterialApp(
title: 'Flutter Demo',
theme: ThemeData(
primarySwatch: Colors.purple,
buttonTheme: ButtonThemeData(
buttonColor: Colors.purple.shade400,
),
visualDensity: VisualDensity.adaptivePlatformDensity,
),
home: BillSpitApp(),
);
}
}
class BillSpitApp extends StatefulWidget {
BillSpitApp({Key key}) : super(key: key);
#override
_BillSpitAppState createState() => _BillSpitAppState();
}
class _BillSpitAppState extends State<BillSpitApp> {
int amount;
int numOfPersons;
double splitAmount;
GlobalKey<FormState> _formKey = GlobalKey<FormState>();
#override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
title: Text("Bill split app"),
),
body: Padding(
padding: const EdgeInsets.all(15.0),
child: Form(
key: _formKey,
child: Column(
mainAxisAlignment: MainAxisAlignment.center,
children: <Widget>[
Text(
splitAmount == null
? "Fill the details and click on calculate to get your bill split"
: "Bill split is ${splitAmount.toStringAsFixed(2)}",
style: TextStyle(
fontSize: 25,
),
textAlign: TextAlign.center,
),
Padding(
padding: const EdgeInsets.symmetric(vertical: 15.0),
child: TextFormField(
keyboardType: TextInputType.number,
validator: (value) {
print("validator amount value $value");
if (value.isEmpty) {
return "Enter some amount";
} else if (double.parse(value).toInt() <= 0) {
return "Amount should be greater than 0";
}
return null;
},
onSaved: (value) {
print("onSaved amount value $value");
amount = int.parse(value);
//int.parse(value);
},
decoration: InputDecoration(
labelText: "Amount",
hintText: "1000",
border: OutlineInputBorder(),
),
),
),
TextFormField(
validator: (value) {
print("person value $value");
if (value.isEmpty) {
return "Enter number of persons";
} else if (double.parse(value).toInt() <= 0) {
return "Number should be greater than 0";
}
return null;
},
onSaved: (value) {
print("onsave numOfPersons $value");
numOfPersons = int.parse(value);
},
keyboardType: TextInputType.number,
decoration: InputDecoration(
labelText: "Number of persons",
hintText: "5",
border: OutlineInputBorder(),
),
),
Padding(
padding: const EdgeInsets.only(top: 15.0),
child: RaisedButton(
child: Text(
"Calculate",
style: TextStyle(color: Colors.white),
),
onPressed: () {
if (_formKey.currentState.validate()) {
_formKey.currentState.save();
print("calculate $amount");
print("calculate $numOfPersons");
setState(() {
splitAmount = amount / numOfPersons;
});
}
},
),
),
],
),
),
),
);
}
}

Answer 2

It is not flutter bug however when you take amount as integer any value starts with 0, flutter takes it as 0.
if (value.isEmpty) {
return "Enter some amount";
} else if (double.parse(value) <= 0) {
return "Amount should be greater than 0";
}
return null;
and
onChanged: (value) {
amount = double.parse(value);
},