flutter changenotifier sample

main.dart

import 'package:flutter/material.dart';
import 'package:provider/provider.dart';

void main() {
  runApp(ChangeNotifierProvider(
    create: (_) => ExampleModel(),
    child: Example(),
  ));
}

class Example extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
        home: Consumer<ExampleModel>(
      child: GestureDetector(
        child: const Text(
          "increase tap",
          style: TextStyle(fontSize: 30),
        ),
        onTap: () {
          context.read<ExampleModel>().increaseCount();
        },
      ),
      builder: (context, model, child) {
        return Column(
          children: [
            const SizedBox(
              height: 30,
            ),
            Text("count: ${model.counter}"),
            const SizedBox(
              height: 30,
            ),
            if (child != null) child
          ],
        );
      },
    ));
  }
}

class ExampleModel with ChangeNotifier {
  int counter = 0;

  increaseCount() {
    counter++;
    notifyListeners();
  }
}