๐ฑ Top 50 Android Developer Interview Questions and Answers
๐ฑ Top 50 Android Developer Interview Questions and Answers
(Written by Rehan Khan)
Basic Android Concepts
1️⃣ What is Android?
Android is an open-source operating system developed by Google. It is primarily designed for touchscreen mobile devices such as smartphones and tablets.
2️⃣ What is an Activity?
An Activity represents a single screen with a user interface, where users can interact with the app.
3️⃣ What is the lifecycle of an Activity?
An Activity has the following lifecycle methods:
onCreate() → onStart() → onResume() → onPause() → onStop() → onDestroy()
4️⃣ What is a Service?
A Service is a component that performs background tasks without providing a user interface.
5️⃣ What is BroadcastReceiver?
BroadcastReceiver allows apps to listen and respond to system-wide events or broadcasts.
6️⃣ What is ContentProvider?
ContentProvider manages access to a structured set of data and allows apps to share data with other apps.
7️⃣ What is an Intent?
Intent is an object that enables communication between app components.
8️⃣ What is an Implicit Intent?
An implicit intent does not name a target component. Instead, it declares a general action to perform.
9️⃣ What is an Explicit Intent?
An explicit intent specifies the component to start by its class name.
10️⃣ What is a Fragment?
A Fragment is a reusable portion of the app’s UI, which can be embedded in an Activity.
Intermediate Concepts
11️⃣ Difference between Service and IntentService?
Service runs on the main thread. IntentService runs on a background thread.
12️⃣ What is ANR (Application Not Responding)?
ANR occurs when the app's main thread is blocked for too long, causing the app to become unresponsive.
13️⃣ What is AndroidManifest.xml?
This is a configuration file where you declare app components, permissions, and other app-level settings.
14️⃣ What is Gradle?
Gradle is the build system used in Android to compile and package apps.
15️⃣ What is ProGuard?
ProGuard is a tool that helps shrink, obfuscate, and optimize your app’s code.
16️⃣ What is Dalvik?
Dalvik was the process virtual machine used in older Android versions to run apps.
17️⃣ What is ART?
ART (Android Runtime) is the virtual machine that runs Android apps, replacing Dalvik for better performance.
18️⃣ What is ViewGroup?
A ViewGroup is a container that holds and organizes multiple views.
19️⃣ Difference between Serializable and Parcelable?
Parcelable is optimized for Android and faster than Serializable, making it the preferred method for object serialization.
20️⃣ What is Handler?
Handler is used to manage and schedule messages and runnable objects on a thread.
Advanced Concepts
21️⃣ What is LiveData?
LiveData is a lifecycle-aware observable data holder class used for UI updates.
22️⃣ What is ViewModel?
ViewModel stores and manages UI-related data in a lifecycle-conscious way.
23️⃣ What is Data Binding?
Data Binding allows binding UI components in layouts directly to data sources.
24️⃣ What is Room Database?
Room is a library that provides an abstraction layer over SQLite to allow for more robust database access.
25️⃣ What is Retrofit?
Retrofit is a type-safe HTTP client for Android that simplifies API calls.
26️⃣ What is OkHttp?
OkHttp is an efficient HTTP & HTTP/2 client for Android and Java applications.
27️⃣ What are Coroutines?
Coroutines are a way to write asynchronous and non-blocking code in Kotlin.
28️⃣ What is WorkManager?
WorkManager is an API for scheduling background work that needs to be guaranteed to run.
29️⃣ Difference between Service and WorkManager?
WorkManager is lifecycle-aware and suitable for background tasks that must run, even if the app exits. Service requires manual management.
30️⃣ What is Navigation Component?
Navigation Component helps manage navigation within an app, including fragment transactions and back stack handling.
Architecture and Design Patterns
31️⃣ What is MVVM architecture?
MVVM stands for Model-View-ViewModel. It separates the UI, business logic, and data.
32️⃣ What is the role of Repository in MVVM?
Repository acts as a single source of truth for data operations and abstracts data sources from the ViewModel.
33️⃣ What is Dependency Injection?
Dependency Injection is a design pattern that provides objects that an object depends on, rather than having it create them itself.
34️⃣ What is Dagger?
Dagger is a popular dependency injection framework used in Android apps.
35️⃣ What is Hilt?
Hilt is a modern DI library for Android that is built on top of Dagger.
36️⃣ What is Jetpack?
Jetpack is a suite of libraries and tools to help developers write high-quality Android apps faster.
37️⃣ What is the Paging Library?
Paging Library helps load large data sets gradually and efficiently.
38️⃣ What is StateFlow?
StateFlow is a state-holder observable flow that emits state updates to collectors.
39️⃣ Difference between LiveData and StateFlow?
LiveData is lifecycle-aware and used for UI updates. StateFlow works seamlessly with coroutines and is not lifecycle-aware.
40️⃣ What is Jetpack Compose?
Jetpack Compose is a modern toolkit for building native Android UIs using a declarative approach.
Testing and Optimization
41️⃣ What is Espresso?
Espresso is a framework for writing UI tests in Android.
42️⃣ What is JUnit?
JUnit is a framework for unit testing Java code.
43️⃣ What is Robolectric?
Robolectric allows Android tests to run inside the JVM without the need for an emulator or device.
44️⃣ How can you optimize app performance?
- Minimize overdraw
- Use efficient layouts
- Avoid memory leaks
- Optimize API calls
- Use RecyclerView instead of ListView
45️⃣ Which tools help detect memory leaks?
LeakCanary and Android Profiler are popular tools for memory leak detection.
Additional Concepts
46️⃣ What is Android Jetpack Compose?
It is a modern UI toolkit for Android that enables developers to create UIs with less code using a declarative programming model.
47️⃣ What is the difference between dp, sp, and px?
- dp: Density-independent pixels (used for UI layout)
- sp: Scale-independent pixels (used for text sizes)
- px: Pixels (physical screen pixels)
48️⃣ How do you handle permissions in Android?
By requesting permissions at runtime using ActivityCompat.requestPermissions() or the new registerForActivityResult API.
49️⃣ What is PendingIntent?
PendingIntent allows another app or component to perform an action on behalf of your app.
50️⃣ What are lifecycle-aware components?
These are components that respect the lifecycle of app components such as Activities and Fragments to prevent memory leaks and optimize performance.
Android Basics
1️⃣ What are the main components of Android?
Activities, Services, BroadcastReceivers, ContentProviders.
2️⃣ What is the role of Context in Android?
Context provides access to application-specific resources and classes.
3️⃣ What is an Application class?
The Application class maintains global application state.
4️⃣ What is a Task in Android?
A Task is a collection of activities that users interact with when performing a certain job.
5️⃣ What is a back stack?
A stack that stores activities in the order they are opened. It manages navigation using the back button.
6️⃣ What is a Toast?
A Toast is a small popup used to show brief messages to the user.
7️⃣ What is SharedPreferences?
A simple way to store small amounts of primitive data as key-value pairs.
8️⃣ What is Internal Storage in Android?
A private storage space where app files are saved.
9️⃣ What is External Storage in Android?
Storage that is accessible to other apps and the user.
10️⃣ What is an APK file?
APK stands for Android Package Kit — the file format used to distribute and install Android apps.
User Interface
11️⃣ What is ConstraintLayout?
A flexible layout that allows you to position and size widgets using constraints.
12️⃣ What is RelativeLayout?
A layout where child views are positioned relative to each other or the parent.
13️⃣ What is RecyclerView?
A more advanced and flexible version of ListView used for displaying large sets of data.
14️⃣ What is the difference between RecyclerView and ListView?
RecyclerView is more efficient, supports layout animations, and provides more flexibility than ListView.
15️⃣ What is CardView?
CardView is a component that displays information inside a card with a shadow and corner radius.
16️⃣ What is Snackbar?
A lightweight message bar that provides brief feedback about an operation.
17️⃣ What is a Dialog?
A small window that prompts the user to make a decision or enter information.
18️⃣ How can you create a custom dialog?
You can create a custom dialog using the Dialog class and inflating a custom layout.
19️⃣ What is ViewPager?
A layout manager that allows the user to flip left and right through pages of data.
20️⃣ What is TabLayout?
A component that provides a horizontal layout to display tabs.
Android Storage & Data
21️⃣ What is SQLite?
SQLite is a lightweight, embedded relational database used in Android for local data storage.
22️⃣ What is the difference between SQLite and Room?
Room provides an abstraction layer over SQLite and allows compile-time checking of SQL queries.
23️⃣ What is ContentValues?
ContentValues is a key-value pair collection used to insert and update rows in a database.
24️⃣ What is Cursor?
Cursor is an interface that provides random read-write access to the result set returned by a database query.
25️⃣ What is a Loader?
A Loader loads data asynchronously for an Activity or Fragment.
26️⃣ What is the purpose of ContentResolver?
ContentResolver provides access to content providers.
27️⃣ What is FileProvider?
FileProvider is a special subclass of ContentProvider that facilitates secure sharing of files.
28️⃣ What is Room DAO?
DAO (Data Access Object) defines methods for accessing the database in Room.
29️⃣ What is a Migration in Room?
A migration is a way to preserve existing data when you change your database schema.
30️⃣ What is a Singleton pattern?
A design pattern where a class has only one instance throughout the application lifecycle.
Kotlin & Modern Android
31️⃣ What is Kotlin?
Kotlin is a modern, statically typed programming language that is officially supported for Android development.
32️⃣ What are Kotlin Coroutines?
Coroutines simplify asynchronous programming by allowing code to be suspended and resumed.
33️⃣ What is a suspend function in Kotlin?
A suspend function is a function that can be paused and resumed later.
34️⃣ What is Flow in Kotlin?
Flow is a cold asynchronous data stream that emits multiple values sequentially.
35️⃣ What is the difference between Flow and LiveData?
Flow is not lifecycle-aware and integrates well with coroutines, while LiveData is lifecycle-aware.
36️⃣ What is Extension Function in Kotlin?
An Extension Function adds new functionality to an existing class without modifying its source code.
37️⃣ What is a Higher-order function?
A function that takes functions as parameters or returns a function.
38️⃣ What is Kotlin Sealed Class?
A sealed class restricts class hierarchy to a known set of types.
39️⃣ What is Inline function in Kotlin?
An Inline function allows the compiler to insert the function's body where it is called, improving performance.
40️⃣ What is Kotlin Null Safety?
Kotlin's type system helps eliminate null pointer exceptions by distinguishing between nullable and non-nullable types.
Advanced Topics
41️⃣ What is Jetpack DataStore?
A modern data storage solution for replacing SharedPreferences.
42️⃣ What is Hilt ViewModel injection?
Hilt simplifies ViewModel injection by automatically providing dependencies.
43️⃣ What is LifecycleOwner?
An interface representing classes that have an Android lifecycle, such as Activity or Fragment.
44️⃣ What is SavedStateHandle?
SavedStateHandle allows you to save and restore UI-related state data in ViewModels.
45️⃣ What is ViewBinding?
ViewBinding generates binding classes that provide references to views in layouts.
46️⃣ What is Android Keystore System?
A system that allows secure storage and usage of cryptographic keys.
47️⃣ What is StrictMode?
StrictMode helps developers detect accidental disk or network access on the main thread.
48️⃣ What is Multidex?
Multidex allows your app to have multiple DEX files when the 65K method limit is exceeded.
49️⃣ What is Instant App?
Instant Apps allow users to try out part of an app without installing it.
50️⃣ What is App Bundle?
An App Bundle is a publishing format that includes all your app’s compiled code and resources.
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