Tag: dart

Why a ListView in a Column throws 'Vertical viewport was given unbounded height', and the four fixes (Expanded, Flexible, shrinkWrap, SizedBox) with the performance trade-offs that decide which one you want.

This crash means you read a late field before anything assigned it. Initialize it synchronously in initState, or stop using late and model the async value as nullable state.

The ! operator hit a null at runtime. Replace it with ?. and ?? for a safe default, or guard with an explicit null check, instead of asserting a value that was not there.

Build a persistent shell with nested routes using ShellRoute and StatefulShellRoute, then wire up path-based deep links that rebuild the full page stack. Full config for Android and iOS, plus the gotchas that break the back stack.

Capture what you need from the context before the await, then guard the resume with if (context.mounted) return. Here is the full pattern, the lint that enforces it, and the edge cases it misses.

A version-pinned guide to moving a legacy Flutter 2.x app to a current Flutter 3.x release, with the sound null safety migration as the hard gate: why you need a two-hop path through Dart 2.19, what dart migrate does, and what breaks along the way.

A step-by-step migration from the provider package to Riverpod 3.x in a real Flutter app: ChangeNotifierProvider to Notifier, MultiProvider to ProviderScope, context.watch to ref.watch, ProxyProvider to ref.watch composition, plus the equality and lifecycle gotchas that bite. Tested on Flutter 3.27.1, Dart 3.11, provider 6.1.5, flutter_riverpod 3.3.1.

Use FutureBuilder or StreamBuilder for a self-contained, throwaway async widget. Reach for Riverpod AsyncValue once the result is shared, cached, or mutated. Here is the decision, the gotchas, and runnable code for both. Tested on Flutter 3.44 and flutter_riverpod 3.3.1.

This crash means a WidgetRef was used after its widget left the tree, usually in an async callback. Read what you need before the await, then guard with a mounted check.

This crash means you called context.of() after the widget left the tree, usually in an async callback or dispose(). Capture the value before the await, or in didChangeDependencies().