If you want to use setState then you should use StatefulWidget instead of a StatelessWidget, I am assuming you are trying to setState on a stateless widget.
Below is the example to explain you how to use setState with stateful widget:
class HomePage extends StatefulWidget { const HomePage({Key? key}) : super(key: key); @override State<HomePage> createState() => _HomePageState(); } class _HomePageState extends State<HomePage> { int incrementValue = 0; @override Widget build(BuildContext context) { return Scaffold( backgroundColor: Colors.white, body: InkWell( onTap: () { setState(() { //write code here incrementValue++; }); }, child: Text("Press Here $incrementValue"), )); } }