Advanced interview questions in Flutter & Dart, page 2
Diagnosing and fixing CustomPainter jank
Avoid work in paint, gate repaints with shouldRepaint, isolate with RepaintBoundary, cache static layers.
Building a custom implicitly animated widget
Extend ImplicitlyAnimatedWidget, use AnimatedWidgetBaseState, define tweens in forEachTween, read values in build.
Present full-screen native SDK UI from Flutter and return a result
This tests platform channel architecture for full-screen native UI delegation. Use MethodChannel to launch the native controller, retain the async result callback, serialize the dismissal payload back to Dart, and avoid PlatformView for modal flows.
What is Pigeon and how does it improve platform channels?
This tests type-safe platform channels versus manual MethodChannel boilerplate. Answer: Pigeon is a dev-time code generator that creates typed host stubs from a Dart contract, removing string keys and encoding. Red flag: calling it a runtime library.
How do you diagnose and fix flaky Flutter widget tests?
Audit unawaited futures, swap pumpAndSettle for explicit pumps or mock timers, and reproduce with logs.
Debug iOS code signing failure in CI that works locally
This tests Xcode code signing and CI keychain isolation. A strong answer checks exportOptions.plist, keychain profile presence, runner OS and Xcode versions, and entitlements mismatches. Red flag: manual local fixes or ignoring keychain access gaps.
What is a Dart Isolate and how does it differ from threads?
Tests Dart's shared-nothing concurrency model. Define an isolate as an independent heap plus event loop, contrast it with shared-memory threads, and explain UI isolate communication via async message ports.
When would you implement a CustomPainter and how does shouldRepaint work?
Use CustomPainter for charts; check fields in shouldRepaint to skip frames; pass Listenable to bypass build layout.
What is Flutter tree shaking and how does it reduce app size?
Tests Dart AOT dead code elimination. Covers compile-time dead code removal, smaller binaries, faster startup, and practices like avoiding dart:mirrors and using const constructors. Red flag: confusing it with minification or runtime stripping.
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