Android Engineer Interview Questions 2025

 Kotlin

• Difference Between const val and val?

• What is Data Class in Kotlin?

• What are the different Coroutine Scopes?

• How to manage series and parallel execution?

• Difference between Flow/SharedFlow/StateFlow and elaborate it.

• What happens if we call .cancel() from a coroutine scope?

• What is an Init block in Kotlin?

• How to choose between apply and with?

• What is inline function in Kotlin?

• Difference between Coroutine and Java Thread

• Why Coroutines are light weight?

• How does Coroutine switch context?

• When to use Kotlin sealed classes?

• Suspending vs Blocking in Kotlin Coroutines

• What are Dispatchers and Name all of them

• On which thread Dispatchers .Default execute the task or use which thread?

• Dispatchers .Default vs Dispatcher .IO

• What is SupervisorScope?

• Exception Handling in Coroutine

• Map vs FlatMap in kotlin

• Singleton Pattern in Kotlin with object keyword

• Collections API in Kotlin

• What is Unidirectional Flow

• StateFlow vs SharedFlow

• Builder Pattern in Kotlin

• Higher Order Functions in Kotlin

• Covariance in Kotlin

• Delay vs Thread.sleep?

• Is singleton thread-safe? vs Object?

Android

• How does Garbage collection works?

• What is a dangling pointer?

• Elaborate Memory Leak?

• Explain fragment Lifecycle when it comes to ViewPager and sliding between different fragments.

• Difference between FragmentStateAdapter and FragmentStatePagerAdapter.

• Difference between Serializable and Parcelable? What are the disadvantages of Serializable?

• How you could implement observable SharedPrefs or observable Databases i.e. Observe a certain key/table/query?

• How does layout inflation work from xml tags to view references in memory?

• What is a Thread, Handler, Looper, and Message Queue?

• What are the different methods of concurrency on Android? Can you explain the difference between ExecutorService vs CachedThreadPool vs FixedThreadPool vs AsyncTasks vs HandlerThreads?

• How does ViewModel instance provide to Activity and Fragment? How does ViewModelProviderStore decide when to retain the instance?

• How do you inspect and solve the Jank issue?

• How does the OutOfMemory happen?

• How do you find memory leaks in Android applications?

• What is Doze? What about App Standby?

• What does setContentView do?

• Process of creating a custom view

• Deeplink understanding and architecture

• Notifications

• Difference between Fragment Lifecycle Observer and View Lifecycle Observer.

• When should you use a Fragment rather than an Activity?

• Explain the Android push notification system.

• How LiveData is different from ObservableField?

• What is the difference between setValue and postValue in LiveData?

• What is process death?

• What is ViewModelScope and How does it work internally?

Lifecycle

• How to keep a video maintain a playing state when we rotate the screen?

• How many callbacks are in Fragments?

• What could be the reasons why onPause didn't get triggered?

• What kind of events trigger onPause() to run?

• In what scenario does the "onDestory" get called directly after "onCreate"?

• Which callback gets called on Activity when an AlertDialog is shown?

• What's the lifecycle in PIP (Picture-in-Picture)?

• What happens if you rotate the device?

• Inside a viewpager (Fragment state pager adapter) what will be the lifecycle of the fragments when you swap from one tab to another?

• Why onActivityCreated is now depreciated in Fragment?

• Which callback should I use if I want to know when my activity came to the foreground?

• When is onActivityResult called?

• What does setRetainInstance do and how you can avoid it?

• What callbacks trigger when a Dialog opens up? In both cases, the dialog is attached from the same activity/fragment and another activity/fragment.

• What do launchWhenCreated, launchWhenStarted, and launchWhenResumed functions do?

• Fragment Callbacks when moving from one fragment to another and coming back to prev one?

• Does onCreateView get called after coming to a fragment from top fragment?

• When does ViewModel not survive?

Networking

• What is the role of OkHttp and Retrofit?

• What design pattern does Retrofit use?

• How would optimize the handling of access token expiration? How would you handle a retry network call when the API fails? (Custom Interceptor response)

WebView

• What are the problems around security when dealing with WebView?

• How to interact or make connections with JavaScript?

Dependency Injection

• Provides vs binds

• Subcomponent vs. component dependency, what is the difference under the hood

• What is a subcomponent and what is its use? How do you use qualifiers or how would you provide different instances of a class with the same data type? Constructor Injection V/s Method Injection? What is the scope? Singleton Annotation?

• What is Circular dependency in dagger? and how to resolve it

• What's interesting about Hilt?

• Did you use Koin? What are your thoughts on it?

Jetpack Compose

• How to launch a coroutine from a composable function?

• How to launch a coroutine from a non-composable function, but tied to composition?

• What is recomposition?

• What is remember in Jetpack Compose?

• Why and when to use remember {}?

• Difference between LazyColumn and RecyclerView?

• What is AndroidView in compose?

• What is the lifecycle of composeables? Lifecycle

• How to avoid recomposition of any composable, if the state is not changed? Smart Recomposition

• What are stable types that can skip recomposition?

• What is State?

• What is MutableState and how does recomposition happen?

• How to retain State across recomposition and configuration changes?

• Difference between Stateless and Stateful composeables?

• What are your thoughts on flat hierarchy, constraint Layout in compose vs. the older view hierarchy in xml

• Difference b/w remember and LaunchedEffect
• Does re-composition of ComposeItem1 bring any effect on ComposeItem2? If yes, then how?
• What is CompositionLocal?

• Custom views in compose

• Canvas in Compose

• What are the benefits of Jetpack Compose?

• How does Jetpack Compose integrate with existing Android frameworks and libraries?

• What are the best practices for performance optimization in Jetpack Compose?

• How is navigation handled in Jetpack Compose?

• What is Strong Skipping Mode?

Thread

• Different types of threads?

• Difference between different types of thread?

• Thread <-> Handler <-> looper

• UI vs Background Thread

• How do you know when some process if blocking a UI thread?

Architecture

• What are SOLID principles?

• What is MVVM?

• Brief about Android Architecture.

• MVP vs MVVM?

• Is there any issue in the Presenter in the MVP?

• Clean Architecture

• MVVM vs MVI

• What is Clean Architecture in MVVM

• What are Provides and Binds in your Dagger library

Design Patterns

• What is SOLID principle?

• What are different design patterns you know about?

• What is a creational pattern?

• What is a structural pattern?

• What is a behavioral pattern?

• Create Singleton Pattern without Kotlin default implementation

• Create Observer Pattern

• Create Adapter Pattern

• How to make a Singleton Pattern Thread Safe?

• What is Dependency Inversion

• Write a real-life example of Dependency Injection without using any library

• Explain how Android Architecture components (ViewModel, LiveData, etc.) utilize design patterns behind the scenes

System Design

• Design Image Loading Library

• Design Image Downloading Library

• Design LRU Cache

• Design a real-time Twitter feed timeline. How will you structure the backend? Will you use WebSocket or REST for this use case? Justify.

• Design Networking Library

• Design Checkout Screen

• Design Error handling Structure

• REST <-> Web Sockets

• Implement caching mechanism

• Build an offline-first app

• Design Analytics Library

Libraries

• How does Glide internally work?

• How does retrofit work internally?

• ViewModel internal working

• How will you choose between Dagger 2 and Dagger-Hilt?

Common Questions

• String vs StringBuilder
• == vs .equals?
• === vs ==?
• Java OOP concepts

• ComposeParent() { ComposeItem1 {} ComposeItem2() {...} }