Flutter StatefulBuilder Widget | Example

Flutter statefulBuilder widget saves app performance and makes it faster. Some expensive operations could be replaced with this.

StatefulBuilder works with a callback function. This callback function triggers rebuild.

import 'package:flutter/material.dart';

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

class MyApp extends StatelessWidget {
  const MyApp({Key? key}) : super(key: key);

  // This widget is the root of your application.
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      debugShowCheckedModeBanner: false,
      theme: ThemeData(
        primarySwatch: Colors.amber,
      ),
      home: const MyHomePage(),
    );
  }
}

class MyHomePage extends StatelessWidget {
  const MyHomePage({Key? key}) : super(key: key);

  @override
  Widget build(BuildContext context) {
    int count = 0;
    return Scaffold(
      appBar: AppBar(title: const Text('StatefulBuilder')),
      body: Padding(
        padding: const EdgeInsets.all(30),
        child: Center(
          child: Column(
            children: [
              StatefulBuilder(builder: (context, myStateFunc){
                return Column(
                  children: [
                    Container(
                      width: 300,height: 300,
                      decoration: const BoxDecoration(
                          color: Colors.red, shape: BoxShape.circle),
                      child: Center(
                        child: Text(
                          count.toString(),
                          style: const TextStyle(fontSize: 80, color: Colors.white),
                        ),
                      ),
                    ),
                    const SizedBox(height: 20),
                    ElevatedButton.icon(
                        onPressed: () {
                          // Call setInnerState function
                            myStateFunc(()=>count++);
                        },
                        icon: const Icon(Icons.add),
                        label: const Text('Increase By One')),
                  ],
                );
              }),
              const SizedBox(height: 100,),
              const ElevatedButton(onPressed: null, child: Text("Not rebuild widget"))
            ],
          ),
        ),
      ),
    );
  }
}