Tag: dart

flutter attach has no --flavor option, so the resident compiler it spawns never defines FLUTTER_APP_FLAVOR and the appFlavor const collapses to null on the first hot restart. Three fixes: default-flavor in pubspec.yaml, flutter run --use-application-binary, and a platform channel that reads the flavor natively. Verified on Flutter 3.47.2 / Dart 3.13.2.

onChanged never fires because no edit happens, and on iOS the engine's deleteBackward returns without touching anything when the field is empty. Two approaches that actually work on every platform: a zero-width sentinel that guarantees an edit, and a single EditableText behind painted cells. Verified on Flutter 3.47.2 / Dart 3.13.2.

ref.watch subscribes and rebuilds, ref.read reads once and never rebuilds. Use watch in every build method and read only inside event callbacks. Here is the decision matrix, the source of both methods in flutter_riverpod 3.4.3, and the four silent failure modes: watch in a callback, read in a provider body, read on an autoDispose provider, and read used as an optimization.

A Key is the identity half of Widget.canUpdate, the one line of framework code that decides whether an Element and its State are reused or thrown away. Here is what that means in practice, the exact list edits that corrupt state without keys, which key type to reach for, and where the key has to sit to work.

A step-by-step migration off the deprecated dart:html, dart:js_util, and package:js onto package:web 1.1.1 and dart:js_interop: how to find every offending import with the dart2wasm compiler, what dart fix does and does not rename, the JSImmutableListWrapper and innerHTML traps, and how to verify with flutter build web --wasm.

The full migration off package:flutter/material.dart and package:flutter/cupertino.dart onto material_ui 1.1.1 and cupertino_ui 1.0.2: what dart fix --code=migrate_design_widgets rewrites, why third-party widgets start throwing ancestor-lookup errors, what MaterialUiCompatibilityBridge actually fixes, and how the flutter_localizations dependency changes.

Firebase Auth restores the Android session from a private SharedPreferences file with no network call, so a release-only sign-out is never broken persistence. It is a different google-services.json, a rejected token refresh, App Check, or your own catch block.

build_runner fails to compile because source_gen 3.1.0 or 4.0.0 calls an analyzer API removed in analyzer 8.4.0. Upgrade the generator that pins source_gen below 4.0.1.

A thread shares memory with every other thread in the process. A Dart isolate does not: it owns its heap, runs one event loop, and talks to other isolates only by messages. Here is what that means at the VM level, where isolate groups blur the line, and how it plays out in Flutter, FFI, and on the web.

Inside testWidgets the ambient clock from package:clock is already fake, but it starts at whatever wall time the test began. Pin it for a whole suite by overriding runTest on a custom AutomatedTestWidgetsFlutterBinding installed from flutter_test_config.dart. Verified on Flutter 3.44.2, clock 1.1.2, fake_async 1.3.3.