Android Interview Questions

Abhinay Gupta

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3 min read

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Jul 15, 2023

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Kotlin

• What is the difference between const val and val?
• What is so interesting about data class?
• Is singleton thread-safe? vs Object?
• What are different type of scope modifiers?
• What are different Coroutine Scope?
• 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?
• How does extension functions work?
• @JvmStatic , static and Companion object
• Kotlin vs Java
• Parcelable vs Serializable

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 ViewModelProviderStoredecide 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?

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.
• How ViewModel retains the data in screen orientation?
• MVVM , MVI, MVC, MVP difference
• Design Patterns

Libraries

• How Glide internally works?
• Hoe does retrofit workss internally?
• ViewModel internal working
• Proguard Working and Use

Common Question

• String vs StringBuilder
• == vs .equals?
• === vs ==?
• Java OOP concepts
• val vs const
• inline keyword
• lateinit vs lazy
• fragments & their lifecycle, Activity lifecycle, Views, Layouts