setState() within StatefulWidget not working properly - flutter

Question

The thing I'm trying to do is, to change the colour of a RawMaterialButton when the button is clicked. Read about StatefulWidget and it seemed like it should work, but for some reason it doesn't.
flutter: Another exception was thrown: setState() called in constructor: ButtonTest#1a93b(lifecycle state: created, no widget, not mounted)
ButtonTest class:
class ButtonState extends StatefulWidget {
#override
State createState() => ButtonTest();
}
class ButtonTest extends State<ButtonState> implements Cipher {
#override
String icon = '';
#override
String title = '';
bool enabled = false;
#override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
title: Text(this.title),
),
body: RawMaterialButton(
shape: CircleBorder(side: BorderSide(color: Colors.black)),
fillColor: enabled ? Colors.blue : Colors.red,
onPressed: () {
setState(() {
this.enabled = true;
});
},
padding: EdgeInsets.all(0)),
);
}
}
Cipher class:
abstract class Cipher {
String icon;
String title;
Widget build(BuildContext context);
}
getCiphers()
getCiphers() {
final List<Cipher> ciphers = new List();
ciphers.add(ButtonTest());
return ciphers;
}
Main class:
void main() => runApp(CipherTools());
class CipherTools extends StatelessWidget {
#override
Widget build(BuildContext context) {
return MaterialApp(
title: 'CipherTools',
theme: ThemeData(
primarySwatch: Colors.blue,
),
home: CipherScreen(
ciphers: getCiphers(),
),
);
}
}
class CipherScreen extends StatelessWidget {
final List<Cipher> ciphers;
CipherScreen({Key key, #required this.ciphers}) : super(key: key);
#override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
title: Text('Ciphers'),
),
body: ListView.builder(
itemCount: ciphers.length,
itemBuilder: (context, index) {
return ListTile(
title: Text(ciphers[index].title),
// When a user taps on the ListTile, navigate to the DetailScreen.
// Notice that we're not only creating a DetailScreen, we're
// also passing the current todo through to it!
onTap: () {
Navigator.push(
context,
MaterialPageRoute(
builder: (context) => DetailScreen(cipher: ciphers[index]),
),
);
},
);
},
),
);
}
}
class DetailScreen extends StatelessWidget {
// Declare a field that holds the Todo
final Cipher cipher;
// In the constructor, require a Todo
DetailScreen({Key key, #required this.cipher}) : super(key: key);
#override
Widget build(BuildContext context) {
return cipher.build(context);
}
}
What am I doing wrong here?

Answer 1

Wrap setState() like this.
if(this.mounted) {
setState(() {
this.enabled = true;
});
}

Answer 2

A couple of things:
ButtonState should be called ButtonTest because this is the
StatefulWidget
ButtonTest should be called ButtonTestState because this is the State.
Then in DetailScreen, in the build() method, you could return the StatefulWidget (ButtonTest), like this:
#override
Widget build(BuildContext context) {
return ButtonTest();
}