Flutter State

main.dart

// View in DartPad: https://dartpad.dev/f19da3d75bda0e05d6e0f976864ec9b2

import 'package:flutter/material.dart';

final Color darkBlue = Color.fromARGB(255, 18, 32, 47);

void main() {
  runApp(MyApp());
}

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      theme: ThemeData.dark().copyWith(scaffoldBackgroundColor: darkBlue),
      debugShowCheckedModeBanner: false,
      home: Scaffold(
        body: Center(
          child: TestWidget(),
        ),
      ),
    );
  }
}

class TestWidget extends StatefulWidget {
  @override
  _TestWidgetState createState() => _TestWidgetState();
}

class _TestWidgetState extends State<TestWidget> {
  int _count = 100;

  @override
  Widget build(BuildContext context) {
    return TextButton(
        child: Text("Hello Stooart!! $_count"),
        onPressed: () {
          setState(() {
            this._count -= 1;
          });
        });
  }
}