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Tag: dart

61 posts · Page 4 of 7

2026-06-14 errors flutter dart

Fix: Looking up a deactivated widget's ancestor is unsafe in Flutter

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().

2026-06-09 flutter dart futurebuilder

How to Initialize a Future So FutureBuilder Doesn't Recreate It on Every Rebuild in Flutter

FutureBuilder re-runs your async work every time the parent rebuilds because you created the Future inside build. Hoist it into State.initState (or memoize it), and FutureBuilder will reuse the same Future. Here is the why, the repro, and every variant that bites.

2026-06-04 dart flutter

Dart 3.12 Ships Primary Constructors Behind an Experiment Flag

Dart 3.12 adds an experimental primary constructors syntax that declares fields and a constructor in the class header, collapsing the classic three-line data class to one.

2026-06-04 comparison flutter dart

Provider vs Riverpod vs Bloc for Flutter state management in 2026

Pick Riverpod for most new Flutter apps in 2026. Choose Bloc for large teams that want an enforced event-driven structure, and keep Provider only for legacy code.

2026-06-03 errors flutter dart

Fix: RenderBox was not laid out in Flutter

RenderBox was not laid out is almost always a secondary error. Find the first layout assertion above it, usually a scrollable given unbounded constraints, and fix that.

2026-06-03 errors flutter dart

Fix: A TextEditingController was used after being disposed in Flutter

This crash means code touched a controller after dispose() ran. Guard async callbacks with a mounted check, and never dispose a controller you do not own.

2026-06-02 errors flutter dart

Fix: setState() or markNeedsBuild() called during build in Flutter

This error means you mutated state while Flutter was building. Move the setState out of build, or defer it with addPostFrameCallback. Here is why it happens and the right fix.

2026-06-02 flutter dart riverpod

How to Show Loading and Error States with AsyncValue in Flutter Riverpod

Render loading, data, and error UI from a single AsyncValue in Riverpod 3. Use AsyncNotifier and AsyncValue.guard for mutations, .when() and switch pattern matching for the UI, keep previous data on refresh, and migrate the legacy StateNotifier pattern. Tested on flutter_riverpod 3.x, Flutter 3.44, Dart 3.x.

2026-06-01 flutter dart memory

How to Dispose Controllers in Flutter to Avoid Memory Leaks

AnimationController, TextEditingController, and ScrollController hold resources that Dart's GC cannot reclaim until you dispose them. Here is the correct pattern, the ordering rules, and how to catch leaks before they ship.

2026-06-01 flutter dart networking

How to Handle Network Errors Gracefully in a Flutter App

A request can fail with no connectivity, a timeout, a DNS failure, a 500, or malformed JSON, and each needs a different response. Here is how to catch the right exceptions, classify them, retry safely, and show a UI a user can act on.