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Android Interview Questions and Answers

1. What is Android?
Android is an open-source mobile operating system developed by Google. It is based on the Linux kernel and is designed for touchscreen devices such as smartphones and tablets.
2. What are the main components of Android architecture?
Android architecture consists of:

Linux Kernel – Handles device drivers and hardware interaction.
Libraries – Includes SQLite, WebKit, Media Framework, etc.
Android Runtime (ART/Dalvik VM) – Executes Android applications.
Application Framework – Manages UI, activity lifecycle, and other services.
Applications – User-installed apps and pre-installed system apps.

3. What are the main components of an Android application?
The four main components are:

Activities – UI screens of an app.
Services – Background processes running without UI.
Broadcast Receivers – Listens for system-wide or app-specific events.
Content Providers – Shares data between apps (e.g., SQLite database).

4. What is an Activity in Android?
An Activity represents a single screen in an Android app. It contains UI elements and interacts with users.
5. What is an Intent in Android?
An Intent is a messaging object used for communication between components (e.g., launching activities, starting services, or broadcasting messages).
Example:
val intent = Intent(this, SecondActivity::class.java) startActivity(intent)
6. What is the difference between Implicit and Explicit Intent?

Implicit Intent – Does not specify the target component (e.g., opening a URL in a browser).
Explicit Intent – Specifies the exact component to launch (e.g., opening a specific activity).

7. What is a Service in Android?
A Service is a background task that runs independently of the UI.
Example: Playing music in the background.
8. What is a Broadcast Receiver?
A Broadcast Receiver listens for and responds to system-wide or app-specific broadcast messages.
Example: Receiving a notification when battery is low.
9. What is a Content Provider in Android?
A Content Provider allows different applications to share data. Example: Contacts app shares contacts with messaging apps.
10. What is an Android Manifest file?
The AndroidManifest.xml file contains essential app information, including:

Package name
App components (activities, services, etc.)
Permissions (e.g., Internet access)

11. What is an APK?
An APK (Android Package Kit) is the file format for distributing and installing Android apps.
12. What is the difference between onCreate(), onStart(), and onResume()?

onCreate() – Called when the activity is first created.
onStart() – Called when the activity becomes visible.
onResume() – Called when the activity starts interacting with the user.

13. What is SharedPreferences in Android?
SharedPreferences is a key-value storage mechanism for saving small amounts of data persistently.
Example: Saving a username.
val sharedPref = getSharedPreferences("MyPrefs", Context.MODE_PRIVATE) sharedPref.edit().putString("username", "John").apply()
14. What is SQLite in Android?
SQLite is a lightweight database used for local storage in Android apps.
15. What is the difference between dp, sp, and px in Android?

dp (Density-independent Pixels) – Scales for different screen sizes.
sp (Scale-independent Pixels) – Similar to dp but adjusts for font size settings.
px (Pixels) – Actual screen pixels (not recommended for UI).

16. What is RecyclerView?
A RecyclerView is an advanced version of ListView used for displaying large datasets efficiently with improved scrolling performance.
17. What is ViewModel in Android?
ViewModel is a part of Jetpack Architecture Components, used for storing UI-related data even when the activity is recreated (e.g., during screen rotation).
18. What is LiveData?
LiveData is an observable data holder class that updates UI components when the data changes.
19. What is the purpose of Gradle in Android development?
Gradle is a build automation tool used to manage dependencies and compile Android applications.
20. How do you handle permissions in Android?
Permissions are declared in AndroidManifest.xml and requested at runtime.
Example: Requesting camera permission.
ActivityCompat.requestPermissions(this, arrayOf(Manifest.permission.CAMERA), 101)
21. What is ProGuard in Android?
ProGuard is a tool used to shrink, optimize, and obfuscate the code to protect it from reverse engineering.
22. What is the difference between Fragment and Activity?

Activity: Represents a complete screen in an app.
Fragment: A UI component that can be reused within activities.

23. What is ANR (Application Not Responding)?
ANR occurs when the main UI thread is blocked for too long, causing the app to become unresponsive.
24. What is Dependency Injection in Android?
Dependency Injection (DI) is a design pattern used to manage dependencies. Popular DI frameworks in Android include Dagger and Hilt.
25. What is Jetpack Compose?
Jetpack Compose is a modern UI toolkit for Android that allows building declarative and reactive UI using Kotlin code instead of XML.

1. What is the difference between Serializable and Parcelable in Android?

Serializable: Uses Java’s default serialization (slower, requires reflection).
Parcelable: Optimized for Android (faster, better performance).

2. How does ViewModel help in Android development?

ViewModel stores UI-related data to survive configuration changes (like screen rotation), preventing unnecessary reloading.

3. What is LiveData, and why is it useful?

LiveData is an observable data holder that updates UI components automatically when data changes.

4. What is the difference between ConstraintLayout and RelativeLayout?

ConstraintLayout: More flexible, efficient, and reduces nesting.
RelativeLayout: Older, can lead to deep hierarchies.

5. What is the difference between implicit and explicit intent?

Implicit Intent: Requests an action from another app without specifying the component.
Explicit Intent: Specifies the exact activity or service to launch.

6. How does the Activity lifecycle work?

The main lifecycle methods:

onCreate() → onStart() → onResume() → (Active State)
onPause() → onStop() → onDestroy()

7. What is WorkManager in Android?

WorkManager is a Jetpack library for managing background tasks, ensuring execution even after app restarts.

8. How does Data Binding work in Android?

Data Binding connects UI components to data sources directly in XML, reducing boilerplate code.
Example:

9. What is the difference between MVVM and MVP architecture?

MVVM (Model-View-ViewModel): Google-recommended, UI observes data changes.
MVP (Model-View-Presenter): Presenter handles UI logic directly.

10. How do you communicate between Fragments?

Using a ViewModel shared between fragments or an Interface to pass data.

11. What is the difference between Service and IntentService?

Service: Runs in the background indefinitely.
IntentService: Stops automatically when the task is completed.

12. What is the purpose of Coroutines in Android?

Coroutines handle asynchronous programming efficiently using suspend functions instead of callbacks.

13. How do you implement Dependency Injection in Android?

Using Hilt:

@Module @InstallIn(SingletonComponent::class) object AppModule { @Provides fun provideRepository(): Repository = Repository() }

14. How do you handle API calls in Android using Retrofit?

Retrofit is a popular HTTP client library.

interface ApiService { @GET("users") suspend fun getUsers(): List<User> }

15. What is Paging Library in Android?

The Paging Library efficiently loads large datasets in chunks, improving performance.

16. How do you prevent memory leaks in Android?

Avoid static references to Activity.
Use WeakReference.
Use Lifecycle-aware components.

17. What is Room Database?

Room is a Jetpack library for SQLite database management, providing an abstraction over SQLite.

18. What is the difference between SharedPreferences and DataStore?

SharedPreferences: XML-based key-value storage, synchronous.
DataStore: Uses Kotlin Coroutines, more efficient and async.

19. How does Navigation Component improve navigation?

Handles Fragment transactions automatically.
Supports safe arguments to pass data.
Manages back stack efficiently.

20. What is the function of ProGuard in Android?

ProGuard shrinks, optimizes, and obfuscates code to prevent reverse engineering.

21. What are BroadcastReceivers used for?

They listen for system-wide events like network changes, battery level, or SMS received.

22. What is ViewBinding in Android?

ViewBinding simplifies UI element binding by removing the need for findViewById().

23. How do you optimize battery performance in an Android app?

Use WorkManager for background tasks.
Minimize WakeLocks.
Optimize location updates.

24. What is the difference between a Dialog and a BottomSheet?

Dialog: Small pop-up window that requires user interaction.
BottomSheet: UI element that slides up from the bottom.

25. How do you implement push notifications in Android?

Using Firebase Cloud Messaging (FCM):

FirebaseMessaging.getInstance().subscribeToTopic("news")

1. What is Jetpack Compose, and how does it differ from XML-based UI?

Jetpack Compose is a modern UI toolkit for building native Android apps using Kotlin-based declarative programming instead of XML. It offers:

Faster UI updates using state management.
Less boilerplate code compared to XML layouts.
Better performance through direct UI rendering.

2. What is the difference between LiveData and StateFlow?

LiveData: Lifecycle-aware, used with UI components.
StateFlow: A cold stream that emits state changes, more suited for ViewModel logic.

3. How does WorkManager compare with JobScheduler and AlarmManager?

WorkManager: Best for persistent and deferrable background tasks.
JobScheduler: Good for API 21+ but not lifecycle-aware.
AlarmManager: Best for exact-time execution but inefficient for periodic tasks.

4. What is the purpose of Dagger and Hilt in Android?

Dagger and Hilt are Dependency Injection (DI) frameworks that:

Reduce boilerplate code.
Improve testability by injecting dependencies.
Manage object creation efficiently.

5. How does Navigation Component improve Fragment navigation?

Manages back stack automatically.
Supports SafeArgs to pass data between fragments safely.
Handles deep linking efficiently.

6. What is Data Binding, and how does it work?

Data Binding allows direct binding of UI components to data sources in XML, reducing boilerplate code:

binding.viewModel = viewModel

7. What are Coroutines, and how do they work in Android?

Coroutines simplify asynchronous programming using suspend functions and launch to execute background tasks efficiently:

GlobalScope.launch { val data = fetchData() withContext(Dispatchers.Main) { updateUI(data) } }

8. What is Flow, and how does it compare to LiveData?

Flow: Cold stream, supports multiple emissions (better for real-time data).
LiveData: Hot stream, lifecycle-aware, UI-focused.

9. What are Sealed Classes in Kotlin?

Sealed classes restrict subclass inheritance to only predefined types, useful for handling API responses:

sealed class Result { object Success : Result() object Error : Result() }

10. How do you handle multi-threading in Android?

Using Coroutines (recommended), Executors, or RxJava for concurrency and background processing.

11. What is Paging 3, and how does it improve list performance?

Paging 3 is a Jetpack library that:

Loads data incrementally to improve efficiency.
Works with Room, Retrofit, and Flow.
Supports built-in caching and error handling.

12. How do you implement Dependency Injection in Android using Hilt?

@Module @InstallIn(ActivityComponent::class) object AppModule { @Provides fun provideRepository(): Repository = Repository() }

13. What is ViewModelScope, and why is it used?

ViewModelScope launches coroutines tied to a ViewModel, ensuring automatic cancellation when the ViewModel is destroyed.

14. What is the difference between FragmentStateAdapter and FragmentPagerAdapter?

FragmentStateAdapter: Best for large datasets (destroys fragments not in use).
FragmentPagerAdapter: Keeps all fragments in memory, suitable for small lists.

15. How does WorkManager handle constraints like network availability?

WorkManager allows setting conditions for execution:

val workRequest = OneTimeWorkRequestBuilder<MyWorker>() .setConstraints( Constraints.Builder().setRequiredNetworkType(NetworkType.CONNECTED).build() ) .build()

16. What is ProGuard, and how does it protect Android apps?

ProGuard shrinks, optimizes, and obfuscates code to protect it from reverse engineering.

17. How do you use Retrofit with Kotlin Coroutines?

interface ApiService { @GET("users") suspend fun getUsers(): List<User> }

18. What is MotionLayout, and how does it improve animations?

MotionLayout is a constraint-based animation system that enables complex motion transitions within XML.

19. What is Jetpack Datastore, and how does it compare to SharedPreferences?

DataStore: Uses Coroutines, better for structured storage.
SharedPreferences: XML-based, synchronous, can cause UI lag.

20. What is the difference between Local Broadcast and Global Broadcast?

Local Broadcast: Sent within the app, more efficient.
Global Broadcast: Sent system-wide, consumes more resources.

21. How do you handle configuration changes in Android?

Use ViewModel to retain UI data.
Set configChanges in AndroidManifest.xml.
Use onSaveInstanceState() for small data persistence.

22. What are Unidirectional Data Flows (UDF) in Android?

UDF ensures data flows in a single direction, reducing UI inconsistencies. Example: MVI (Model-View-Intent) architecture.

23. How does Firebase Remote Config work?

Remote Config updates app behavior without publishing a new version by changing values from Firebase Console.

24. What are WorkManager’s Backoff Policies?

WorkManager retries failed tasks using Exponential Backoff (recommended) or Linear Backoff.

25. How do you optimize RecyclerView performance?

Use DiffUtil for efficient updates.
Enable ViewHolder recycling.
Prefetch data using RecyclerView.setItemViewCacheSize().

1. What is Android?

Answer: Android is an open-source mobile operating system developed by Google, based on the Linux kernel. It is used for developing applications for smartphones, tablets, TVs, and other embedded systems.

2. What are the core components of Android?

Answer:

Activities – UI components for user interaction
Services – Background processes without UI
Broadcast Receivers – Handle system-wide events
Content Providers – Manage shared app data

3. What is the Android Activity Lifecycle?

Answer: The activity lifecycle consists of:

onCreate() – Initializes the activity
onStart() – Activity is visible
onResume() – User interacts with the app
onPause() – Activity partially visible
onStop() – Activity is hidden
onDestroy() – Activity is removed from memory

4. What is an Intent in Android?

Answer: An Intent is used to navigate between activities, pass data, or trigger system events.
Example:

val intent = Intent(this, SecondActivity::class.java) startActivity(intent)

5. What is the difference between Implicit and Explicit Intent?

Answer:

Explicit Intent – Specifies the exact activity to launch.
Implicit Intent – Used when the target component is unknown, such as opening a web page.

6. What is a Service in Android?

Answer: A Service is a background process that does not have a UI. It is used for long-running tasks like music playback or fetching data.

7. What is a Broadcast Receiver?

Answer: A BroadcastReceiver listens for system-wide events such as battery low, incoming SMS, or network changes.

Example:

class MyReceiver : BroadcastReceiver() { override fun onReceive(context: Context?, intent: Intent?) { Log.d("Receiver", "Broadcast received") } }

8. What is a Content Provider in Android?

Answer: Content Providers manage shared application data such as contacts, media, and settings.

9. What is the difference between ViewModel and LiveData?

Answer:

ViewModel – Stores UI-related data that survives configuration changes.
LiveData – Observable data holder class that updates UI when data changes.

10. What is MVVM Architecture?

Answer: MVVM (Model-View-ViewModel) separates UI logic from business logic.

Model – Manages data
ViewModel – Handles UI logic
View – Displays UI

11. What is the difference between RecyclerView and ListView?

Answer:

RecyclerView is more efficient and supports dynamic layouts.
ListView is less flexible and outdated.

12. How do you handle API calls in Android?

Answer: Using Retrofit for network requests:

interface ApiService { @GET("users") fun getUsers(): Call<List<User>> }

13. What is the Room Database in Android?

Answer: Room is an ORM (Object-Relational Mapping) library for SQLite database in Android.

Example:

@Entity data class User(@PrimaryKey val id: Int, val name: String)

14. What is SharedPreferences in Android?

Answer: A lightweight storage mechanism for storing key-value pairs.

val sharedPreferences = getSharedPreferences("MyPrefs", Context.MODE_PRIVATE) sharedPreferences.edit().putString("username", "John").apply()

15. How do you implement Dependency Injection in Android?

Answer: Using Dagger Hilt:

@Module @InstallIn(SingletonComponent::class) object AppModule { @Provides fun provideRepository(): MyRepository = MyRepository() }

16. How do you optimize Android app performance?

Answer:

Use RecyclerView with ViewHolder pattern.
Use Jetpack Compose for UI optimization.
Use WorkManager for background tasks.
Optimize memory usage with LeakCanary.

17. What is WorkManager in Android?

Answer: WorkManager handles background tasks that need to run even if the app is closed.

Example:

class MyWorker(appContext: Context, workerParams: WorkerParameters) : Worker(appContext, workerParams) { override fun doWork(): Result { Log.d("Worker", "Task executed") return Result.success() } }

18. How does Android handle multi-threading?

Answer: Using:

Thread – Basic multi-threading
AsyncTask – (Deprecated) Background tasks
Coroutines – Efficient async programming
WorkManager – Background tasks with constraints

19. What is Jetpack Compose?

Answer: Jetpack Compose is Google’s modern UI toolkit that simplifies UI development with declarative Kotlin-based syntax.

Example:

@Composable fun Greeting(name: String) { Text(text = "Hello, $name!") }

20. How do you implement push notifications in Android?

Answer: Using Firebase Cloud Messaging (FCM):

FirebaseMessaging.getInstance().subscribeToTopic("news")

21. How do you secure an Android app?

Answer:

Use ProGuard to obfuscate code.
Store API keys in Android Keystore.
Implement SSL Pinning for secure network communication.

22. How do you handle permissions in Android?

Answer:

if (ContextCompat.checkSelfPermission(this, Manifest.permission.CAMERA) == PackageManager.PERMISSION_GRANTED) { // Permission granted } else { ActivityCompat.requestPermissions(this, arrayOf(Manifest.permission.CAMERA), REQUEST_CODE) }

23. What are Android Fragments?

Answer: Fragments represent UI components inside an Activity and allow modular UI design for different screen sizes.

24. What is ViewBinding in Android?

Answer: ViewBinding is a feature that eliminates findViewById() and improves UI interaction.

Example:

val binding = ActivityMainBinding.inflate(layoutInflater) setContentView(binding.root) binding.textView.text = "Hello, Android!"

25. How do you test Android applications?

Answer:

Unit Testing – JUnit for logic testing.
UI Testing – Espresso for UI automation.
Mocking – Mockito for dependency testing.

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Android Interview Questions and Answers

Top 100 Android Interview Questions for Freshers

1. What is Android?
Android is an open-source mobile operating system developed by Google. It is based on the Linux kernel and is designed for touchscreen devices such as smartphones and tablets.
2. What are the main components of Android architecture?
Android architecture consists of:

Linux Kernel – Handles device drivers and hardware interaction.

Libraries – Includes SQLite, WebKit, Media Framework, etc.

Android Runtime (ART/Dalvik VM) – Executes Android applications.

Application Framework – Manages UI, activity lifecycle, and other services.

Applications – User-installed apps and pre-installed system apps.

3. What are the main components of an Android application?
The four main components are:

Activities – UI screens of an app.

Services – Background processes running without UI.

Broadcast Receivers – Listens for system-wide or app-specific events.

Content Providers – Shares data between apps (e.g., SQLite database).

Implicit Intent – Does not specify the target component (e.g., opening a URL in a browser).

Explicit Intent – Specifies the exact component to launch (e.g., opening a specific activity).

Package name

App components (activities, services, etc.)

Permissions (e.g., Internet access)

11. What is an APK?
An APK (Android Package Kit) is the file format for distributing and installing Android apps.
12. What is the difference between onCreate(), onStart(), and onResume()?

onCreate() – Called when the activity is first created.

onStart() – Called when the activity becomes visible.

onResume() – Called when the activity starts interacting with the user.

dp (Density-independent Pixels) – Scales for different screen sizes.

sp (Scale-independent Pixels) – Similar to dp but adjusts for font size settings.

px (Pixels) – Actual screen pixels (not recommended for UI).

Activity: Represents a complete screen in an app.

Fragment: A UI component that can be reused within activities.

"Deep Concepts to Elevate Your Career"

This guide provides 100+ Android interview questions along with in-depth concepts to strengthen your expertise.

Courses

Contact Us

Android Interview Questions and Answers

Top 100 Android Interview Questions for Freshers

1. What is Android? Android is an open-source mobile operating system developed by Google. It is based on the Linux kernel and is designed for touchscreen devices such as smartphones and tablets. 2. What are the main components of Android architecture? Android architecture consists of:

Linux Kernel – Handles device drivers and hardware interaction.

Libraries – Includes SQLite, WebKit, Media Framework, etc.

Android Runtime (ART/Dalvik VM) – Executes Android applications.

Application Framework – Manages UI, activity lifecycle, and other services.

Applications – User-installed apps and pre-installed system apps.

3. What are the main components of an Android application? The four main components are:

Activities – UI screens of an app.

Services – Background processes running without UI.

Broadcast Receivers – Listens for system-wide or app-specific events.

Content Providers – Shares data between apps (e.g., SQLite database).

Implicit Intent – Does not specify the target component (e.g., opening a URL in a browser).

Explicit Intent – Specifies the exact component to launch (e.g., opening a specific activity).

Package name

App components (activities, services, etc.)

Permissions (e.g., Internet access)

11. What is an APK? An APK (Android Package Kit) is the file format for distributing and installing Android apps. 12. What is the difference between onCreate(), onStart(), and onResume()?

onCreate() – Called when the activity is first created.

onStart() – Called when the activity becomes visible.

onResume() – Called when the activity starts interacting with the user.

dp (Density-independent Pixels) – Scales for different screen sizes.

sp (Scale-independent Pixels) – Similar to dp but adjusts for font size settings.

px (Pixels) – Actual screen pixels (not recommended for UI).

Activity: Represents a complete screen in an app.

Fragment: A UI component that can be reused within activities.

"Deep Concepts to Elevate Your Career"

This guide provides 100+ Android interview questions along with in-depth concepts to strengthen your expertise.

Courses

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1. What is Android?
Android is an open-source mobile operating system developed by Google. It is based on the Linux kernel and is designed for touchscreen devices such as smartphones and tablets.
2. What are the main components of Android architecture?
Android architecture consists of:

3. What are the main components of an Android application?
The four main components are:

11. What is an APK?
An APK (Android Package Kit) is the file format for distributing and installing Android apps.
12. What is the difference between onCreate(), onStart(), and onResume()?