Flutter Debugging

Logging

• Use a centralized AppLogger class for all logging — NEVER use print() or raw debugPrint()
• Define log levels: verbose, debug, info, warning, error, fatal
• In dev flavor: log everything (verbose and above)
• In staging: log info and above
• In production: log warning and above only, route to Crashlytics
• Include context in logs: AppLogger.error('Failed to fetch user', error: e, stackTrace: st)
• NEVER log sensitive data (passwords, tokens, PII) at any level

Flutter DevTools

• Use Widget Inspector to debug layout issues and identify unnecessary rebuilds
• Use Performance Overlay (showPerformanceOverlay: true) to monitor frame rates
• Use Timeline View to identify jank — target 16ms per frame (60fps)
• Use Memory View to detect memory leaks and monitor allocation patterns
• Use Network Profiler to inspect Dio requests/responses during development

Debugging Strategies

• Layout Issues: Use debugPaintSizeEnabled = true to visualize widget boundaries
• Overflow Errors: Check RenderFlex overflowed — use Expanded, Flexible, or constrain dimensions
• Unbounded Height: Wrap ListView in SizedBox or use shrinkWrap: true with NeverScrollableScrollPhysics
• Rebuild Tracking: Add debugPrint('$runtimeType rebuild') temporarily to identify excessive rebuilds — remove before commit
• Async Errors: Always catch and log errors in try-catch blocks with stack traces
• Use assert() for development-time invariant checks that are stripped in release builds

Memory Management

• Dispose ALL controllers, subscriptions, Timer, and AnimationController in dispose()
• Use late initialization in initState() — never inline-initialize disposable objects
• Use WeakReference for caches that should not prevent garbage collection
• Profile memory with DevTools Memory tab — watch for monotonically increasing allocations
• Watch for common leaks: undisposed listeners, closures capturing BuildContext, global streams without cancellation

Performance Profiling

• Always profile with --profile mode (not debug): flutter run --profile --flavor dev -t lib/main_dev.dart
• Use Timeline.startSync / Timeline.finishSync for custom performance tracing of critical paths
• Monitor shader compilation jank on first run — use --cache-sksl for warmup:

  flutter run --profile --cache-sksl --purge-persistent-cache
  

• Target metrics: < 16ms frame build time, < 100ms screen transition, < 2s cold start

Error Boundaries

• Route errors to Crashlytics in staging/prod (FlutterError.onError = FirebaseCrashlytics.instance.recordFlutterFatalError)
• Set FlutterError.onError and PlatformDispatcher.instance.onError to catch framework and async errors
• Wrap critical widget subtrees in custom error boundary widgets that show fallback UI instead of red screens
• In release mode: NEVER show stack traces to users — show user-friendly error messages only

Source: dhruvanbhalara/skills — distributed by TomeVault.