checkbox can not see from the interface flutter - dart

Question

1[This is how my page works. I want to get checkbox ticked and get the post paid number then can click the continue button. In my code checkbox is in between text and text form field Why i can not see my check box here and this is my code.]
new Container(
padding: const EdgeInsets.all(40.0),
child: new Form(
child: new Column(
mainAxisAlignment: MainAxisAlignment.start,
children: <Widget>[
new Text(
"Are you a post paid customer",
style: new TextStyle(
color: Colors.blue,
fontSize: 25.0,
),
),
new Checkbox(
activeColor: Colors.blue,
value: _isChecked,
onChanged: (bool val){
onChanged(val);}
),
new TextFormField(
decoration: new InputDecoration(
labelText: "Post Paid Number",
),
obscureText: true,
keyboardType: TextInputType.text,
),
new Padding(
padding: const EdgeInsets.only(top: 60.0),
),
new MaterialButton(
height: 50.0,
minWidth: 150.0,
color: Colors.blue,
splashColor: Colors.blue,
textColor: Colors.white,
child: new Text("Continue"),
onPressed: () {
Navigator.push(
context,
new MaterialPageRoute(builder: (context) => new RegPage()),
);
},
),

Answer 1

Recreated your code and got it working.
You need to change _isChecked in Checkbox's onChanged like:
onChanged: (val) {
setState(() {
_isChecked = !_isChecked;
});
}),
Make sure to do it in setState or the change wont be reflected on UI.
My Code:
import 'package:flutter/material.dart';
import 'package:so_demo/sample_page.dart';
void main() => runApp(new MyApp());
class MyApp extends StatelessWidget {
// This widget is the root of your application.
#override
Widget build(BuildContext context) {
return new MaterialApp(
title: 'Flutter Demo',
theme: new ThemeData(
primarySwatch: Colors.blue,
),
home: new MyHomePage(),
);
}
}
class MyHomePage extends StatefulWidget {
#override
MyHomePageState createState() {
return new MyHomePageState();
}
}
class MyHomePageState extends State<MyHomePage> {
bool _isChecked = false;
#override
Widget build(BuildContext context) {
return new Scaffold(
appBar: new AppBar(
title: new Text('SO HELP'),
),
body: new Container(
padding: const EdgeInsets.all(40.0),
child: new Form(
child: new Column(
mainAxisAlignment: MainAxisAlignment.start,
children: <Widget>[
new Text(
"Are you a post paid customer",
style: new TextStyle(
color: Colors.blue,
fontSize: 25.0,
),
),
new Checkbox(
activeColor: Colors.blue,
value: _isChecked,
onChanged: (val) {
setState(() {
_isChecked = !_isChecked;
});
}),
new TextFormField(
decoration: new InputDecoration(
labelText: "Post Paid Number",
),
obscureText: true,
keyboardType: TextInputType.text,
),
new Padding(
padding: const EdgeInsets.only(top: 60.0),
),
new MaterialButton(
height: 50.0,
minWidth: 150.0,
color: Colors.blue,
splashColor: Colors.blue,
textColor: Colors.white,
child: new Text("Continue"),
onPressed: () {
Navigator.of(context).push(new MaterialPageRoute(builder: (context) => new RegPage());
},
),
]),
),
),
);
}
}