State-management

Who Owns the State? Callbacks & typedef Parent ↔ Child Communication code snippet import 'dart:math'; import 'package:flutter/material.dart'; void main() { runApp(const MyApp()); } class MyApp extends StatelessWidget { const MyApp({super.key}); @override Widget build(BuildContext context) { return MaterialApp( theme: ThemeData(colorScheme: .fromSeed(seedColor: Colors.deepPurple)), home: const MyHomePage(), ); } } class MyHomePage extends StatefulWidget { const MyHomePage({super.key}); @override State<MyHomePage> createState() => _MyHomePageState(); } class _MyHomePageState extends State<MyHomePage> { int _counter = 0; @override Widget build(BuildContext context) { return Scaffold( body: Column( crossAxisAlignment: .stretch, children: [ SectionView( onTap: (v) async { _counter = v; setState(() {}); return "Something went wrong"; }, ), Text( _counter.toString(), style: TextStyle(fontSize: 55), textAlign: .center, ), SectionView( increment: false, onTap: (n) async { _counter = n; await Future.delayed(Duration(seconds: 2)); setState(() {}); return ""; }, ), ], ), ); } } typedef OnSectionViewChange = Future<String> Function(int); class SectionView extends StatefulWidget { const SectionView({super.key, this.increment = true, required this.onTap}); final bool increment; final OnSectionViewChange onTap; @override State<SectionView> createState() => _SectionViewState(); } class _SectionViewState extends State<SectionView> { bool isLoading = false; String errMsg = ""; Future<void> onTap() async { isLoading = true; setState(() {}); Random random = Random(); final number = random.nextInt(4444); errMsg = await widget.onTap(widget.increment ? number : number * -1); isLoading = false; setState(() {}); } @override Widget build(BuildContext context) { return Expanded( child: Material( color: widget.increment ? Colors.blueAccent : Colors.redAccent, child: Center( child: Column( mainAxisSize: .min, children: [ Text(errMsg), InkWell( onTap: isLoading ? null : onTap, child: isLoading ? Center(child: CircularProgressIndicator()) : Icon( widget.increment ? Icons.add : Icons.remove, size: 55, ), ), ], ), ), ), ); } } Why AlertDialog/BottomSheet UI doesn’t update even with setState Widget state 03 ...

FutureBuilder Learn Async Data & avoid common mistakes. future codeSnippet import 'dart:math'; import 'package:flutter/material.dart'; void main() => runApp( const MaterialApp(debugShowCheckedModeBanner: false, home: MyHomePage()), ); class MyHomePage extends StatefulWidget { const MyHomePage({super.key}); @override State<MyHomePage> createState() => _MyHomePageState(); } class _MyHomePageState extends State<MyHomePage> { //... Future<int> fetchData() async { await Future.delayed(Duration(seconds: 4)); final number = Random().nextInt(100); return number; } late Future<int> future = fetchData(); @override Widget build(BuildContext context) { return Scaffold( body: Center( child: FutureBuilder<int>( future: future, initialData: 100, builder: (context, AsyncSnapshot snapshot) { if (snapshot.hasError) { return Text(snapshot.error?.toString() ?? ""); } return Column( mainAxisSize: .min, children: [ if (snapshot.connectionState == ConnectionState.waiting) CircularProgressIndicator(), Text(snapshot.data.toString()), ], ); }, ), ), ); } } StreamBuilder Flutter’s Stream and StreamBuilder in detail. It also shows StreamController, StreamSubscription, stream error handling, single-subscription issue and event management with practical examples. ...

This video covers Provider in Flutter, including ChangeNotifier, ProxyProvider, FutureProvider, StreamProvider, DevTools, and common Provider mistakes. Code Clone the starter codebase Switch to the provider-start branch Continue from there Or just watch the video: Shared_preference Persistent theme with Shared_preference.