Android Engineer Interview Questions

If this Repository helps you, Show your ❤️ by buying me a ☕ below.

Need a Mentor? Click Here

Contents

• Kotlin
• Android
• Lifecycle
• Networking
• Webview
• Dependency Injection
• Jetpack Compose
• Thread
• Architecture
• System Design
• Libraries
• Common Question
• Questions from Company

Kotlin

• What is the difference between const val and val?
  • Both are used to define read-only properties, but
  • const val properties should be initialized at compile-time whereas val properties can be initialized at runtime
  • If we decompile, const val variable will replace with its value but val not, because it can be initialized at runtime

  • const val BASE_URL = "https://github.com"
    val githubHandle = "anandwana001"
    val repoName: String
    

• What is so interesting about data class?
  • Uses to hold data
  • Pre-functions like toString, equals, copy, and componentN
  • Data classes cannot be abstract, open, sealed, or inner.
  • Data classes cannot extend other classes
  • Supports destructuring declaration
• Is singleton thread-safe? vs Object?
• What are the different types of scope functions?
  • Let = T.let { R }
    • lambda result (R) is the return type
    • can be performed on any T type object
    • lambda reference is it
    • suitable for null check
  • Run = T.run { R }
    • same as let, but mostly used in initializing an object
    • lambda reference is this
    • suitable for null check
  • With = with(T) { R }
    • if T is nullable object use run else use with(T)
    • lambda reference is this
    • not suitable for null check
  • Also = T.also { T }
    • when need to perform multiple operations in chain use also
    • lambda reference is it
  • Apply = T.apply { T }
    • when need to perform the operation on the T object and return the same use apply
    • lambda reference is this
    • suitable for null check
• 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?

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 reference 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 provided to Activity and Fragment. How does ViewModelProviderStore decide when to retain the instance?
• How do you inspect and solve Jank issue? here
• How does the OutOfMemory happens?
• 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

Lifecycle

• How to keep a video maintain playing state when we rotate screen?
• How many callbacks in Fragmnets?
• What could be the reasons when 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 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 foreground?
• When is onActivityResult called?
• What does setRetainInstance do and how you can avoid it?
• What callbacks trigger when a Dialog opens up? Conside both case, dialog attached from same activity/fragment and other activity/fragment.
• What does launchWhenCreated, launchWhenStarted, and launchWhenResumed functions do?

Networking

• What is the role of OkHttp and Retrofit?
• What design pattern does Retrofit use?
• How would optimise handling of access token expiration? How would you handle 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 subcomponent and what is the 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 coroutine from a composable function? - LaunchedEffect
• How to launch coroutine from a non-composable function, but tied to composition? - rememberCoroutineScope()
• What is recomposition? Recomposition
• What is remember in compose?
  • A composable function to remember the value produced by a calculation only at the time of composition. It will not calculate again in recomposition.
  • Recomposition will always return the value produced by composition.
  • Whole Compose is based on concept of Positional Memoization
  • At the time of recomosition, remember internally calls a function called rememberedValue() whose work is to look into the slotTable and compare if the previous value and the new value has any difference, if not return, else update value
• 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 which can skip recomposition?
• What is State?
• What is MutableState and how does recomposition happens?
• How to retain State accross recomposition and configuration changes?
• Difference between Stateless and Statefull composeables?
• What are your thoughts on flat heirarchy, constraint Layout in compose vs the older view heirarchy in xml
• Difference b/w remember and LaunchedEffect
• Does re-composition of ComposeItem1 bring any affect on ComposeItem2? If yes, then how?
  • ComposeParent() { ComposeItem1 {} ComposeItem2() {...} }
  • What is CompositionLocal?
• Custom views in compose
• Canvas in Compose

Thread

• Different type of threads?
• Difference between different type of thread?
• Thread <-> Handler <-> looper
• UI vs Background Thread

Architecture

• What is SOLID principles?
• What is MVVM?
• Brief about Android Architecture.

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

Libraries

• How Glide internally works?
• Hoe does retrofit workss internally?
• ViewModel internal working

Common Question

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

Questions from Company

Contributing Guidelines

What interesting questions you had faced while giving interview for Android Engineer role (any level)? Let's open a PR.

If this repository helps you in anyway, show your love ❤️ by putting a ⭐ on this project ✌️