Flutter Cheat Sheet

Updated 2026-04-29

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Flutter is Google's open-source UI framework for building natively compiled, cross-platform applications from a single codebase, targeting mobile (iOS, Android), web, desktop, and embedded devices. Powered by the Dart programming language, Flutter uses a reactive widget tree where everything — from layout containers to buttons — is a widget, enabling composable and declarative UI development. Unlike frameworks that bridge to platform UI components, Flutter renders directly via its Impeller engine (the default on iOS and Android, replacing Skia), delivering pixel-perfect control and 60fps+ performance across all targets. With Dart 3, the language gained records, patterns, and sealed classes — features that fundamentally reduce boilerplate and improve type safety. The key insight: widgets are immutable and stateless by default; state changes trigger rebuilds rather than mutations, and BuildContext is your gateway to navigating ancestors (Theme, Navigator, InheritedWidget) without prop drilling.

What This Cheat Sheet Covers

This topic spans 25 focused tables and 200 indexed concepts. Below is a complete table-by-table outline of this topic, spanning foundational concepts through advanced details.

Table 1: Core Widget TypesTable 2: Layout WidgetsTable 3: Constraint and Sizing WidgetsTable 4: Scrollable WidgetsTable 5: Material Design WidgetsTable 6: Cupertino (iOS-Style) WidgetsTable 7: Input WidgetsTable 8: Gesture Detection WidgetsTable 9: Animation WidgetsTable 10: Navigation and RoutingTable 11: State Management PatternsTable 12: Dart Language BasicsTable 13: Dart Classes and OOPTable 14: Dart CollectionsTable 15: Dart Async ProgrammingTable 16: Theme and StylingTable 17: KeysTable 18: Widget Lifecycle (StatefulWidget)Table 19: Package ManagementTable 20: Images and AssetsTable 21: Platform Channels and PluginsTable 22: Performance OptimizationTable 23: Debugging and DevToolsTable 24: TestingTable 25: Material 3 Updates

Widget	Example	Description
StatelessWidget	`class MyWidget extends StatelessWidget {` `Widget build(context) => Text('Hi');` `}`	• Immutable widget that rebuilds only when parent rebuilds — no internal state • ideal for static UI that depends solely on constructor parameters.
StatefulWidget	`class Counter extends StatefulWidget {` `@override` `_CounterState createState() => _CounterState();` `}`	• Widget that holds mutable state via a paired State object • calling `setState()` triggers rebuild.
State	`class _CounterState extends State<Counter> {` `int count = 0;` `@override Widget build(context) => Text('$count');` `}`	• Mutable companion to StatefulWidget holding data that persists across rebuilds • `initState()`, `dispose()`, and lifecycle methods live here.

Table 1: Core Widget Types

Widget	Example	Description
StatelessWidget	`class MyWidget extends StatelessWidget {` `Widget build(context) => Text('Hi');` `}`	• Immutable widget that rebuilds only when parent rebuilds — no internal state • ideal for static UI that depends solely on constructor parameters.
StatefulWidget	`class Counter extends StatefulWidget {` `@override` `_CounterState createState() => _CounterState();` `}`	• Widget that holds mutable state via a paired State object • calling `setState()` triggers rebuild.
State	`class _CounterState extends State<Counter> {` `int count = 0;` `@override Widget build(context) => Text('$count');` `}`	• Mutable companion to StatefulWidget holding data that persists across rebuilds • `initState()`, `dispose()`, and lifecycle methods live here.