Android Developer interview questions cover Android SDK, Java/Kotlin programming, UI design, lifecycle management, and app deployment. Here are 25 common questions with answers to help you prepare.

Q1. What is Android?

Android is an open-source operating system based on Linux, designed primarily for touchscreen mobile devices like smartphones and tablets.

Q2. What is an Activity in Android?

An Activity represents a single screen with a user interface in an Android app. It acts as an entry point for user interaction.

Q3. Explain the Android Activity Lifecycle.

The Activity lifecycle includes states like onCreate, onStart, onResume, onPause, onStop, and onDestroy, managing how an Activity behaves from creation to destruction.

Q4. What is an Intent?

An Intent is a messaging object used to request an action from another app component, such as starting an Activity or Service.

Q5. What are the different types of Intents?

Explicit Intents specify the target component directly, while Implicit Intents declare a general action to be handled by any capable app.

Q6. What is a Service in Android?

A Service is a component that performs long-running operations in the background without a user interface.

Q7. What is a Content Provider?

Content Providers manage access to a structured set of data and provide mechanisms for data sharing between applications.

Q8. Explain the difference between Serializable and Parcelable.

Both are used for object serialization, but Parcelable is faster and recommended in Android for inter-process communication.

Q9. What is a Fragment?

A Fragment is a reusable portion of the user interface in an Activity, allowing modular UI design and dynamic UI changes.

Q10. How do you handle screen orientation changes in Android?

You can handle orientation changes by saving state in onSaveInstanceState and restoring it in onCreate or by configuring activity to handle config changes.

Q11. What is the difference between dp and px?

dp (density-independent pixels) scales based on screen density, while px (pixels) is an absolute measurement.

Q12. What is ANR?

ANR (Application Not Responding) occurs when the main thread is blocked for too long, causing the app to become unresponsive.

Q13. What is the AndroidManifest.xml file?

The Manifest file declares essential app information like components, permissions, and hardware features.

Q14. What is a Broadcast Receiver?

Broadcast Receivers listen for system-wide or application-specific broadcast messages and respond accordingly.

Q15. What is the difference between Service and IntentService?

IntentService handles asynchronous requests on a separate worker thread and stops itself when done, while Service runs on the main thread.

Q16. How do you optimize battery usage in Android apps?

Reduce background activity, use JobScheduler or WorkManager for deferred tasks, and optimize network and location requests.

Q17. What is Gradle?

Gradle is the build system used in Android Studio to automate building, testing, and packaging Android apps.

Q18. What is RecyclerView?

RecyclerView is a flexible and efficient view for displaying large sets of data in a scrollable list or grid.

Q19. How do you secure data in Android apps?

Use encryption, secure shared preferences, avoid storing sensitive data in plain text, and follow best practices for permissions.

Q20. What is the difference between onCreate() and onStart()?

onCreate() is called when the activity is first created, initializing the UI, while onStart() is called just before the activity becomes visible.

Q21. Explain what LiveData is.

LiveData is an observable data holder class that respects the lifecycle of app components, ensuring UI updates only when active.

Q22. What is ViewModel?

ViewModel is a class designed to store and manage UI-related data in a lifecycle-conscious way to survive configuration changes.

Q23. How does Android handle multiple screen sizes?

Android supports multiple screen sizes using resource qualifiers like layout-small, layout-large, and by using density-independent pixels (dp).

Q24. What is the purpose of ProGuard?

ProGuard shrinks, optimizes, and obfuscates code to reduce app size and make reverse engineering harder.

Q25. How do you perform network operations in Android?

Use libraries like Retrofit, Volley, or make HTTP requests in background threads or with asynchronous tasks to avoid blocking the main thread.