Flutter Interview Questions

Ashutosh Singh
6 min readJun 22, 2022


Google: goo.gle/Flutter_3

I had multiple interviews with organisations while looking for a job in Flutter, therefore in this blog I will go over all of the questions that were asked as well as ones that I prepared. You may occasionally be asked to know some fundamentals about an app’s Native functionality, whether it be for Android or iOS.

Generally in the Flutter job interviews there are 3–4 rounds.

1st round: Assignment or Basic knowledge of Flutter

2nd round: Basic/Advance Flutter questions/Basic Native questions

3rd and 4th round: Advance Flutter questions/Native Mobile questions/System Design of Mobile/Architecture level questions

Flutter Assignments are given to check the candidate’s coding technique some examples are: Todo(using StateManagement or DB), tic-tac-toe, newsApi(using StateManagement or DB), Draw particular Shape using CustomPainter

I’ve answered to some questions here, while in others I’ve provided a link to the topic and tried to put questions of a similar nature together.

Q1: Lifecycle of Stateful Widget

A1: https://flutterbyexample.com/lesson/stateful-widget-lifecycle

Q2: Keys in Flutter: Local, Global & Unique

A2: https://www.raywenderlich.com/22416843-unlocking-your-flutter-widgets-with-keys

Q3: Flutter architectural overview

A3: https://docs.flutter.dev/resources/architectural-overview

Q4: Keyword: static, final & const

A4: https://stackoverflow.com/a/53947036

Q5: Difference between Hot reload and Hot restart

A5: https://stackoverflow.com/a/61787777

Q6: Explain BuildContext

A6: https://api.flutter.dev/flutter/widgets/BuildContext-class.html

Q7: MediaQuery

A7: https://api.flutter.dev/flutter/widgets/MediaQuery-class.html

Q8: How does Flutter run the code on Android?

A8: The NDK for Android compiles the C and C++ code of the flutter engine. Both the SDK's and your Dart code are compiled into native, ARM, and x86 libraries using the AOT (ahead-of-time) compiler. These libraries are included in an Android "runner" project, and the entire item (or artefact) is packaged as an .apk file. The flutter library is loaded when the app is launched.

Q9: How does Flutter run the code on iOS?

A9: LLVM is used to compile the C and C++ code in the Flutter Engine (low level virtual machine — a compiling technology). AOT (ahead-of-time) compiles both the SDK’s and your Dart code into a native, ARM library. The ARM library is included in the iOS project “runner,” and the entire code base is packaged as an iOS App Store Package file .ipa. The flutter library is loaded when the app is launched.

Q10: Stateful vs Stateless Widget

A10: https://medium.com/flutter-community/flutter-stateful-vs-stateless-db325309deae

Q11: How does Dart AOT work?

A11: https://dart.dev/overview#platform

Q12: What is the difference between double.INFINITY and MediaQuery?

A12: double.infinity: As big as my parent allows and MediaQuery: As big as device screen.

Q13: Internationalisation and localisation

A13: https://docs.flutter.dev/development/accessibility-and-localization/internationalization

Q14: What is Dart and why does Flutter use it?

A14: Dart is a garbage-collected object-oriented programming language.
Dart is an AOT compiled native code that allows the majority of Flutter to be written in Dart.
Dart can also be JIT-compiled for lightning-fast development cycles and game-changing workflows (such as Flutter’s rapid reload).
Dart’s declarative nature allows Flutter to avoid the need for a separate declarative layout language like JSX or XML, as well as separate visual interface builders.

Q15: What are the benefits of Flutter?

A15: Learn Once write Everywhere
Cross-platform Development
Faster Development
Good Community
Live and Hot Reloading
Native Performance
Provides Native Look and Feel
Expressive and versatile UI

Q16: Semantics

A16: https://api.flutter.dev/flutter/widgets/Semantics-class.html

Q17: WidgetsBindingObserver

A17: WidgetsBindingObserver check when the system puts the app in the background or returns the app to the foreground

Q18: Null Safety in Dart

A18: https://codewithandrea.com/videos/dart-null-safety-ultimate-guide-non-nullable-types/

Q19: Null-aware operators

A19: ?., ??, & ??=

Q20: Tree shaking

A20: https://medium.com/flutter/optimizing-performance-in-flutter-web-apps-with-tree-shaking-and-deferred-loading-535fbe3cd674

Q21: SizedBox VS Container?

A21: https://stackoverflow.com/a/55716668

Q22: What does resizeToAvoidBottomInset do?

A22: If an onscreen keyboard is presented above the scaffold, using resizeToAvoidBottomInset, body can be adjusted to avoid overlaying the keyboard, allowing widgets inside the body to be seen.

Q23: Flow analysis: Promotion, Definite Assignment

A23: https://codewithandrea.com/videos/dart-null-safety-ultimate-guide-non-nullable-types/#flow-analysis-promotion

Q24: What is vsync?

A24: Vsync keeps track of the screen so that Flutter doesn’t have to render the animation while the screen is not there.

Q25: Ticker

A25: https://api.flutter.dev/flutter/scheduler/Ticker-class.html

Q26: TickerProvider

A26: https://api.flutter.dev/flutter/scheduler/TickerProvider-class.html

Q27: What are tween animations?

A27: https://api.flutter.dev/flutter/animation/Tween-class.html

Q28: Mixins

A28: When we wish to share a behaviour across different classes that aren’t in the same class hierarchy, or when it’s not practical to implement such a behaviour in a superclass, mixins come in handy.

Q29: Expanded vs Flexible

A29: https://stackoverflow.com/a/52646036

Q30: WillPopScope

A30: WillPopScope that allows us to control the back button navigation.

Q31: Spread operator?

A31: https://www.woolha.com/tutorials/dart-using-triple-dot-spread-operator-examples

Q32: When do we use profile mode?

A32: When you wish to analyse performance, you use profile mode. Profile mode on mobile is similar to release mode, with the following exceptions: — Some service extensions have been enabled, such as the one that enables the performance overlay. — Tracing is enabled, and debugging tools (such as DevTools) that support source-level debugging can connect to the process.

Q33: Why is exit(0) not preferred for closing an app?

A33: https://stackoverflow.com/a/57534684

Q34: What is .of method in Flutter and when would you use them ?

A34: https://stackoverflow.com/a/65272618

Q35: How to control the visibility of widget?

A35: https://danledev.medium.com/widget-hide-and-seek-a-guide-to-managing-flutter-widgets-visibility-d7977cbaf444

Q36: Single Instance and Scoped Instance ?

A36: https://codewithandrea.com/articles/global-access-vs-scoped-access/

Q37: Runes in dart

A37: https://api.dart.dev/stable/2.17.4/dart-core/Runes-class.html

Q38: then vs whenComplete

A38: When the longer term completes with a mistake or not, .whenComplete fires a function, whereas .then returns a replacement Future with the results of the decision to onValue (if this future completes with a value) or onError (if this future completes with an error).

Q39: Isolates

A39: https://blog.codemagic.io/understanding-flutter-isolates/

Q40: Parallellism vs Concurrency ?

A40: https://stackoverflow.com/a/53901907

Q41: Package vs plugin

A41: A “package” is a collection of Dart code.
Dart and Native code (kotlin/js/swift) are combined in a “plugin.”

Q42: What if we didn’t dispose controllers?

A42: When a state object is eliminated, the dispose method is used to release the memory assigned to variables.
For example ,if you’re utilising an animation in your app, you’ll need to free up memory assigned to the animationController. Otherwise, the PlayStore and AppStore may issue a memory leaking warning to your programme.

Q43: Flutter engine

A43: https://github.com/flutter/engine/blob/main/README.md

Q44: State restoration

A44: https://medium.com/flutter-community/flutter-state-restoration-restore-scrollviews-and-textfields-d1d35cbd878c

Q45: Constraints

A45: https://docs.flutter.dev/development/ui/layout/constraints

Q46: async vs async* in Dart?

A46: async gives you a Future while async* gives you a Stream.

Q47: Slivers

A47: https://medium.com/flutter/slivers-demystified-6ff68ab0296f

Q48: Custom Painter

A48: https://medium.com/flutter-community/a-deep-dive-into-custompaint-in-flutter-47ab44e3f216 from Deven Joshi

Q49: Ephemeral/App state

A49: https://docs.flutter.dev/development/data-and-backend/state-mgmt/ephemeral-vs-app

Q50: Inherited widget

A50: https://api.flutter.dev/flutter/widgets/InheritedWidget-class.html.

Q51: How is InheritedWidget different from Provider?

A51: InheritedWidgets are used to build the provider. You’ll have hundreds of unnecessary repeating lines if you don’t use provider. Provider simply takes the logic of InheritedWidgets and pares it down to the minimum of boilerplate.

Q52: Value notifier

A52: https://medium.com/@avnishnishad/flutter-communication-between-widgets-using-valuenotifier-and-valuelistenablebuilder-b51ef627a58b

Q53: What do you mean by Streams and its types?

A53: https://medium.com/flutter-community/flutter-stream-basics-for-beginners-eda23e44e32f

Q54: Throttle vs Debounce

A54: https://stackoverflow.com/a/25991510

Q55: How to use extensions?

A55: https://dart.dev/guides/language/extension-methods

Q56: 3 Trees in Flutter

A56: https://medium.com/@omlondhe/flutters-3-tree-architecture-9263b2bd50d1

Q57: How to change state of view in Stateless widget without using any external package?

A57: Stream and ValueListenable

Q58: How do you create a factory?

A58: https://dart.dev/guides/language/language-tour#factory-constructors

Q59: Singleton class

A59: https://stackoverflow.com/a/12649574

Q60: Design Patterns

A60: Learn Design Patterns from Mangirdas Kazlauskas, most asked ones are Singleton, Adapter, Factory, Observer and Composite.

Q61: SOLID DRY KISS Principles

A61: https://vpodk.medium.com/principles-of-software-engineering-6b702faf74a6

Q62: Widgets

A62: In interviews these following widget’s usage and example could be asked: UnconstrainedBox, ConstrainedBox, FittedBox, LayoutBuilder, IntrinsicWidth, IntrinsicHeight

Q63: Splash Screen

A63: https://docs.flutter.dev/development/ui/advanced/splash-screen

Q64: Miscellaneous

A64: Some Miscellaneous flutter topics:-

Reduce App Size


Secure Flutter Apps

Dependency Injection

Deep Linking


Following are the companies who hires for Flutter, most of these companies have team based in INDIA itself: Cardekho, Even, Josh Talks, Geekyants, Awign, Park+, Grab, Gojek, Tokopedia, Frontrow, Jio, YML, Squareboat, Inmobi, Junglee games, Zest Money, Vahak, CoinDCX, Appyboard, RuleZero(Zerodha Backed), CRED, Smallcase, Tickertape, Nas Academy,GetStream, Innovaccer, CaptainFresh, Webengage, PasarPolis, Amazon, Sav.money, Clipboard health, India Today, Hero Vired, Tide, Yatra, Yellow Class, Slice, GreyOrange, Fello, Appyhigh.

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Ashutosh Singh

Flutter | Android | iOS | Python