Flutter

Build reliable Flutter apps avoiding state loss, widget rebuild traps, and async pitfalls.

Quick Reference

Topic	File
setState, state loss, keys	state.md
build method, context, GlobalKey	widgets.md
FutureBuilder, dispose, mounted	async.md
Context after pop, deep linking	navigation.md
const, rebuilds, performance	performance.md
Platform channels, null safety	platform.md

Critical Rules

• setState after dispose — check mounted before calling, crashes otherwise
• Key missing on list items — reordering breaks state, always use keys
• FutureBuilder rebuilds on parent rebuild — triggers future again, cache the Future
• BuildContext after async gap — context may be invalid, check mounted first
• const constructor — prevents rebuilds, use for static widgets
• StatefulWidget recreated — key change or parent rebuild creates new state
• GlobalKey expensive — don't use just to access state, pass callbacks instead
• dispose incomplete — cancel timers, subscriptions, controllers
• Navigator.pop with result — returns Future, don't ignore errors
• ScrollController not disposed — memory leak
• Image caching — use cached_network_image, default doesn't persist
• PlatformException not caught — platform channel calls can throw