how to access to variable from StatefulWidget to State class flutter - flutter

Question

I try to pass data from page one to page two data is pass OK but I have one problem now.
this is my code:
class SecondScreen extends StatefulWidget {
final int itemHolder ;
SecondScreen({Key key, #required this.itemHolder}) : super(key: key);
#override
State<StatefulWidget> createState() {
return new mainState();
}
}
class mainState extends State <SecondScreen> {
bool value = false ;
MyPreferences _myPreferences = MyPreferences();
#override
void initState() {
// TODO: implement initState
super.initState();
initial();
}
void initial() async {
setState(() {
});
}
final String apiURL = 'http://xxxxxxxxx/getFlowersList.php';
Future<List<Flowerdata>> fetchFlowers() async {
var response = await http.get(apiURL);
if (response.statusCode == 200) {
final items = json.decode(response.body).cast<Map<String, dynamic>>();
List<Flowerdata> listOfFruits = items.map<Flowerdata>((json) {
return Flowerdata.fromJson(json);
}).toList();
return listOfFruits;
}
else {
throw Exception('Failed to load data from Server.');
}
}
I try to use var (itemHolder ) in the link like that:
final String apiURL = 'http://xxxxxxx/getFlowersList.php?id=' +itemHolder;
but I get error:
Undefined name 'itemHolder'. Try correcting the name to one that is defined, or defining the name.
I can access to itemHolder. So how can I access to it?

Answer 1

try this:
...
String apiURL;
#override
void initState() {
super.initState();
apiURL = 'http://xxxxxxx/getFlowersList.php?id=' +widget.itemHolder.toString();
}
...

Answer 2

To use the variables declared in the SecondScreen you have to access it with the prefix 'widget' and the dot operator, not directly. Here is the code:
final String apiURL = 'http://xxxxxxx/getFlowersList.php?id=' + widget.itemHolder;
And when you make the variable final, you have to initialize it while declaration or through constructor else delete keyword final: