Flutter developers are often asked about performance, architecture, and tools in interviews. Here is a crisp Q&A guide covering the most important concepts.
1. What is Flutter?
- Flutter is a cross-platform UI toolkit by Google.
- Builds Android, iOS, Web, Desktop apps with a single codebase.
- Uses Dart language and Skia rendering engine.
- Fast UI changes with Hot Reload.
- High performance and rich UI widgets.
2. What is Skia in Flutter?
- A 2D graphics rendering engine.
- Flutter uses Skia to render every pixel.
- Ensures smooth 60–120 FPS performance.
- Consistent UI across different platforms.
- GPU accelerated (OpenGL/Vulkan/Metal).
3. What are Isolates in Flutter?
- Dart’s way of handling multithreading.
- Each isolate has its own memory.
- Prevents UI freezing during heavy tasks.
- Communicates using message passing.
4. What is Clean Architecture in Flutter?
- Separates code into layers for scalability:
- Presentation Layer → UI + State
- Domain Layer → UseCases + Entities
- Data Layer → Repository + Data Sources
- Improves testability and loose coupling.
5. Riverpod vs Provider
| Feature | Riverpod | Provider |
|---|---|---|
| BuildContext dependency | No | Yes |
| Safety | Compile-time checks | Runtime errors possible |
| Memory | Auto disposal | Manual |
| Scalability | High | Medium |
| Testing | Very easy | Requires widget testing |
Summary: Riverpod is more scalable and safer.
6. What is RepaintBoundary?
- Widget that isolates repainting of its child.
- Reduces unnecessary UI redraws.
- Improves performance in animations and lists.
- Helps with screenshot capturing.
7. StatefulWidget Lifecycle
initState → didChangeDependencies → build → didUpdateWidget → setState → deactivate → dispose
initState()→ initialize controllers, API calls.dispose()→ release controllers and streams.
8. What is Hydrated BLoC?
- BLoC extension that automatically persists state.
- State restored after app restart.
- Requires converting state to/from JSON.
- Used for login state, cart data, offline UI.
9. Common Reasons for App Crashes
- Null value errors.
- Unhandled exceptions.
- Heavy operations on UI thread.
- Memory leaks (not disposing controllers).
- Missing permissions or API failures.
10. What are SOLID Principles?
- S — Single Responsibility
- O — Open/Closed
- L — Liskov Substitution
- I — Interface Segregation
- D — Dependency Inversion
Improves maintainability and scalability.
11. What is Interface in Dart?
- Dart has no
interfacekeyword. - Every class acts as an interface.
- Use
implementsto enforce method contracts. - Useful for clean architecture and loose coupling.
12. What are Live Classes?
- Real-time interactive online teaching.
- Students can ask doubts instantly.
- Includes screen sharing, whiteboards.
- Can be recorded for revision.
- Accessible from anywhere.
13. How to Manage Subscriptions?
- Use in-app purchases or payment gateways.
- Maintain subscription state on backend.
- Handle renewals, expiry, and failure cases.
- Analyze retention, churn and conversions.
14. What is Agora?
- Real-time audio and video communication SDK.
- Used for live classes, meetings, webinars.
- Low latency and high quality.
- Supports Flutter and multiple platforms.
- Includes messaging, recording, effects.
15. What is Analytics?
- Tracks user behavior and usage patterns.
- Helps improve product decisions.
- Tools: Firebase Analytics, Mixpanel, Amplitude.
- Measures retention, conversion, engagement.
- Supports event tracking and A/B testing.
Conclusion
These essential Flutter topics are commonly asked in interviews and help you build scalable, high-performance apps.
