Flutter LBS to KG app not registrating "Convert" submit - dart

Question

I'm doing my first Flutter app where I want to take LBS as input and show it as KG.
I've created two double variables, one for _lbs and one for the _kg value.
I have a method that converts lbs input to kg output.
However when I press the Convert button nothing is happening in my app.
import 'package:flutter/material.dart';
void main() => runApp(new MyApp());
class MyApp extends StatelessWidget {
#override
Widget build(BuildContext context) {
final appTitle = 'LBS to KG converter';
return MaterialApp(
title: appTitle,
home: Scaffold(
appBar: AppBar(
title: Text(appTitle),
),
body: MyCustomForm(),
),
);
}
}
// Create a Form Widget
class MyCustomForm extends StatefulWidget {
#override
MyCustomFormState createState() {
return MyCustomFormState();
}
}
// Create a corresponding State class. This class will hold the data related to
// the form.
class MyCustomFormState extends State<MyCustomForm> {
final _formKey = GlobalKey<FormState>();
double _lbs;
double _kg;
void _convert(){
setState(() {
_kg = _lbs * 0.45359237;
});
}
#override
Widget build(BuildContext context) {
return new Form(
key: _formKey,
child: Column(
children: <Widget>[
/*- LBS ---------------- */
new Row(
children: <Widget>[
Flexible(
child: Padding(
padding: const EdgeInsets.only(
top: 2.0, left: 10.0),
child: new Text(
"LBS:",
style: new TextStyle(fontSize: 18.0),
)
),
),
Flexible(
child: Padding(
padding: const EdgeInsets.only(
top: 2.0, left: 10.0),
child: new TextField(decoration: InputDecoration(
hintText: '$_lbs'
),)
),
)
],
),
/*- KG ----------------- */
new Row(
children: <Widget>[
Flexible(
child: Padding(
padding: const EdgeInsets.only(
top: 2.0, left: 10.0),
child: new Text(
"KG:",
style: new TextStyle(fontSize: 18.0),
)
),
),
Flexible(
child: Padding(
padding: const EdgeInsets.only(
top: 2.0, left: 10.0),
child: new TextField(decoration: InputDecoration(
hintText: '$_kg'
),)
),
)
],
),
/*- Convert ---------------- */
new Row(
mainAxisAlignment: MainAxisAlignment.center,
children: <Widget>[
Flexible(
child: Padding(
padding: const EdgeInsets.only(
top: 15.0, right: 10.0, left: 10.0),
child: GestureDetector(
onTap: _convert,
child: new Container(
alignment: Alignment.center,
height: 60.0,
decoration: new BoxDecoration(
color: Color(0xFF18D191),
borderRadius: new BorderRadius.circular(9.0)),
child: new Text("Convert",
style: new TextStyle(
fontSize: 20.0, color: Colors.white))),
),
),
)
],
)
],
),
);
}
}
1) Any suggestions on what I am missing in my app?
2) Is "hintText" the best method of showing the value? Is there not any "TextField.value" ?

Answer 1

final lbsController = TextEditingController();
final kgController = TextEditingController();
void _convert(){
_lbs = lbsController.text; // just add checking for digital input there
setState(() {
_kg = _lbs * 0.45359237;
});
}
And inside build
lbsController.text = _lbs;
kgController.text = _kg;
...
child: new TextField(controller: lbsController, ...