60+ Android Developer Interview Questions and Answers for Freshers

The activity creator is used to create instances of an activity class in Android development.

• The activity creator is responsible for instantiating an activity class.

• It is typically used when starting a new activity from another activity.

• The activity creator can pass data to the new activity through intent extras.

• It is commonly used in the onCreate() method of the calling activity.

• Example: Intent intent = new Intent(this, SecondActivity.class); startActivity(intent);

Dependency Injection is a design pattern where components are given their dependencies rather than creating them.

• Hilt is a dependency injection library for Android that simplifies the implementation of DI in Android apps.

• Hilt generates the necessary classes for DI at compile time, reducing boilerplate code.

• Hilt provides annotations like @HiltAndroidApp, @AndroidEntryPoint, and @Inject to facilitate DI in Android development.

To know what things people want from a phone, conduct market research, analyze user feedback, track industry trends, and consider user demographics.

• Conduct market research to understand consumer preferences

• Analyze user feedback from reviews, surveys, and forums

• Track industry trends and technological advancements

• Consider user demographics and their specific needs

• Examples: larger battery life, better camera quality, faster performance

Constraint layout is more flexible and efficient than relative layout.

• Constraint layout allows for complex layouts with fewer nested views.

• It uses constraints to position and size views relative to other views or parent layout.

• Relative layout positions views relative to each other or parent layout using attributes like 'above', 'below', etc.

• Constraint layout is recommended for complex layouts with many views.

• Relative layout is recommended for simple layouts with few views.

The view is attached to the Fragment during the onAttach() lifecycle event.

• The onAttach() method is called when the Fragment is associated with its host Activity.

• This is the first lifecycle method called after the Fragment is created.

• The onAttach() method receives the Activity as a parameter, allowing the Fragment to interact with its host.

LazyColumn is a vertically scrolling list that only composes and lays out the items that are visible on the screen.

• LazyColumn is part of Jetpack Compose, a modern Android UI toolkit.

• It is used to efficiently display large lists of items by only rendering the items that are currently visible on the screen.

• LazyColumn is similar to RecyclerView in traditional Android development.

• It automatically recycles items as they scroll off the screen, improving performance and reducing mem...read more

To set a view in the middle in ConstraintLayout, use layout_constraintStart_toStartOf, layout_constraintEnd_toEndOf, layout_constraintTop_toTopOf, and layout_constraintBottom_toBottomOf attributes.

• Use layout_constraintStart_toStartOf and layout_constraintEnd_toEndOf to align horizontally in the middle.

• Use layout_constraintTop_toTopOf and layout_constraintBottom_toBottomOf to align vertically in the middle.

• Set both horizontal and vertical constraints to center the view.

OOP is a programming paradigm based on the concept of objects, which can contain data in the form of fields and code in the form of procedures.

• OOP focuses on creating objects that interact with each other to solve problems.

• Objects have attributes (data) and methods (functions) that define their behavior.

• Encapsulation, inheritance, and polymorphism are key principles of OOP.

• Example: In a banking application, a 'Customer' object could have attributes like name and account balan...read more

Modifiers in Jetpack Compose are used to apply styling, layout, and behavior to UI elements.

• Modifiers are used to modify the appearance, layout, and behavior of UI elements in Jetpack Compose.

• They can be used to add padding, alignment, background color, click listeners, and more to UI elements.

• Modifiers are composable functions that can be chained together to create complex UI layouts.

• Examples of modifiers include padding(), background(), clickable(), and align().

Android development features include open-source platform, rich development environment, and extensive libraries.

• Open-source platform allows for customization and flexibility

• Rich development environment with tools like Android Studio

• Extensive libraries for various functionalities like UI, networking, and database

• Support for multiple hardware devices and screen sizes

• Integration with Google services like Maps, Firebase, and Play Store

• Ability to create interactive and engaging u...read more

Java is a high-level programming language used for developing a wide range of applications, including Android apps.

• Java is an object-oriented language.

• It is platform-independent, meaning it can run on any operating system.

• Java uses a virtual machine called the Java Virtual Machine (JVM) to execute code.

• It has a large standard library with built-in classes and methods for common programming tasks.

• Java is known for its simplicity, readability, and robustness.

Yes, I have experience working with ViewPager2 and ListAdapter.

• Implemented ViewPager2 to create swipeable screens in Android apps.

• Utilized ListAdapter to efficiently manage data for RecyclerViews.

• Used ListAdapter's DiffUtil to efficiently update RecyclerView items.

The components of an Android app include activities, services, broadcast receivers, and content providers.

• Activities: UI components that represent a single screen with a user interface.

• Services: Background tasks that run independently of the UI.

• Broadcast Receivers: Respond to system-wide broadcast announcements.

• Content Providers: Manage a shared set of app data.

Syntax for HashMap in Kotlin and Java with values.

• In Kotlin:

• val hashMap = hashMapOf<String, Int>()

• hashMap.put("key1", 1)

• hashMap.put("key2", 2)

• In Java:

• HashMap<String, Integer> hashMap = new HashMap<>();

• hashMap.put("key1", 1);

• hashMap.put("key2", 2);

Kotlin coroutines are a way to perform asynchronous operations in a sequential manner.

• Coroutines are lightweight threads that can be used to perform long-running tasks without blocking the main thread.

• They can be used to simplify asynchronous programming by allowing developers to write code that looks synchronous.

• Coroutines can be launched using 'launch' or 'async' functions.

• They can be cancelled using 'cancel' function.

• Example: 'GlobalScope.launch { println("Hello, World!") ...read more

Yes, an activity can exist without a view in Android.

• An activity can perform background tasks without displaying any UI elements.

• For example, a music player app may have an activity to handle playback controls in the background.

• Activities without views are commonly used for tasks like data processing, network operations, or service handling.

Data can be sent between two activities in Android using Intent with putExtra() method.

• Create an Intent object in the sending activity

• Use putExtra() method to add data to the Intent

• Start the second activity with startActivity() method, passing the Intent

• Retrieve the data in the receiving activity using getIntent() and getExtra()

Use runOnUiThread or withContext(Dispatchers.Main) to update UI in coroutine scope.

• Use runOnUiThread to update UI from a background thread.

• Use withContext(Dispatchers.Main) to switch to the main thread in coroutine scope.

• Example: runOnUiThread { textView.text = "Updated text" }

• Example: withContext(Dispatchers.Main) { textView.text = "Updated text" }

Yes, I have experience working on android mobile apps and integrating third-party services.

• Developed and maintained android apps using Java and Kotlin

• Integrated third-party services like Firebase, Google Maps, and AdMob

• Implemented RESTful APIs to communicate with server-side

• Worked with version control tools like Git and SVN

• Debugged and fixed issues reported by users

To play music in background on Android, use a Service class to handle playback and manage audio focus.

• Create a Service class to handle music playback in the background.

• Request audio focus to ensure your app can play music even when other apps are using audio.

• Use MediaPlayer or ExoPlayer to play audio files.

• Handle media controls and notifications to allow users to control playback from the notification shade.

To implement a service in Android, you need to create a class that extends Service and override its lifecycle methods.

• Create a class that extends Service

• Override lifecycle methods such as onStartCommand() and onDestroy()

• Register the service in the AndroidManifest.xml file

• Start the service using startService() method

Yes, I have worked on a logistics application for a transportation company.

• Developed real-time tracking feature for monitoring delivery vehicles

• Implemented route optimization algorithm to improve efficiency

• Integrated payment gateway for online transactions

• Designed user-friendly interface for customers and drivers

Hashcode is a unique identifier for an object, equals() compares the content of two objects, and == checks if two references point to the same object.

• Hashcode is an integer value generated by a hashing algorithm to uniquely identify an object.

• equals() method is used to compare the content of two objects for equality.

• == operator checks if two references point to the same object in memory.

• Example: String class overrides equals() method to compare the content of two strings, whi...read more

Hot and Cold Flow is a design pattern used in Android development to manage the flow of data between components.

• Hot Flow refers to the flow of data that is actively being observed and updated in real-time.

• Cold Flow refers to the flow of data that is not actively being observed and updated, but can be retrieved when needed.

• Hot Flow is typically used for real-time updates, while Cold Flow is used for fetching data on demand.

HashMap is an unordered collection of key-value pairs, while LinkedHashMap maintains the insertion order of elements.

• HashMap uses hashing technique to store and retrieve elements based on their keys.

• LinkedHashMap extends HashMap and adds a doubly-linked list to maintain the insertion order.

• HashMap allows null values and only one null key, while LinkedHashMap allows null values and null keys.

• Example: HashMap map = new HashMap<>();

• Example: LinkedHashMap linkedMap = new LinkedHa...read more

Light weight operations are simple and quick, heavy weight operations are complex and time-consuming.

• Light weight operations are typically simple and quick to execute.

• Heavy weight operations are usually complex and time-consuming.

• Examples of light weight operations include basic arithmetic calculations.

• Examples of heavy weight operations include complex algorithms or database queries.

The RecyclerView is a flexible view for providing a limited window into a large data set.

• Create a RecyclerView in your layout XML file.

• Define a custom adapter class that extends RecyclerView.Adapter.

• Implement the necessary methods in the adapter class like onCreateViewHolder, onBindViewHolder, and getItemCount.

• Set the adapter to the RecyclerView in your activity or fragment.

• Optionally, you can also implement a layout manager to control the arrangement of items in the Recycler...read more

Activity is a single focused thing that user can do, while Fragment is a modular section of an activity.

• Activity represents a single screen with a user interface, while Fragment represents a behavior or a portion of user interface in an Activity.

• An Activity can contain multiple Fragments, but a Fragment cannot exist independently without an Activity.

• Fragments have their own lifecycle, while they are dependent on the lifecycle of the Activity they are attached to.

• Fragments are...read more

Pagination in Android can be achieved by using libraries like Paging Library or implementing custom pagination logic.

• Use Paging Library provided by Android Architecture Components

• Implement custom pagination logic by loading data in chunks

• Update RecyclerView adapter with new data as user scrolls

Coroutines in Android can be launched using the 'launch' function from the CoroutineScope.

• Use the 'launch' function from the CoroutineScope to start a coroutine.

• Specify the context in which the coroutine should run, such as Dispatchers.Main for the main thread.

• Handle exceptions within the coroutine using try-catch blocks.

• Example: CoroutineScope(Dispatchers.Main).launch { // coroutine code here }

A broadcast receiver is an Android component that allows the system to deliver events or messages to the app.

• Broadcast receivers can be used to listen for system-wide broadcast announcements, such as when the device is booted or when the battery is low.

• They can also be used to receive custom broadcast messages sent by other apps or components within the same app.

• Broadcast receivers are registered in the AndroidManifest.xml file or dynamically in code using the registerReceive...read more

Sealed classes are used to restrict inheritance in Kotlin, allowing a class to have a fixed set of subclasses.

• Sealed classes are declared using the 'sealed' keyword.

• They can only be extended within the same file where they are declared.

• Sealed classes are often used in conjunction with when expressions for exhaustive checking.

A suspend function is a function that can be paused and resumed at a later time without blocking the main thread.

• Suspend functions are used in Kotlin coroutines to perform asynchronous operations.

• They are defined using the 'suspend' keyword in the function signature.

• Suspend functions can only be called from within another suspend function or a coroutine builder like 'launch' or 'async'.

Find the second largest number in a given array.

• Sort the array in descending order

• Return the element at index 1, which is the second largest number

I have worked on various layouts including linear, relative, grid, and constraint layouts.

• Implemented linear layouts to arrange views in a single column or row.

• Utilized relative layouts to position views relative to each other.

• Used grid layouts for displaying data in a grid-like structure.

• Implemented constraint layouts for creating complex and flexible UI designs.

Fragment add vs replace lifecycle methods

• When using add, the fragment's lifecycle methods are called but the view is not recreated

• When using replace, the fragment's view is recreated and its lifecycle methods are called

• Add is useful for retaining the fragment's state, while replace is useful for completely replacing the fragment

Services in Android are components that run in the background to perform long-running operations.

• Services in Android are used to perform tasks in the background without a user interface.

• MVVM (Model-View-ViewModel) is an architectural pattern that separates the UI from the business logic and data.

• MVP (Model-View-Presenter) is another architectural pattern that separates the UI from the business logic and data.

• Room Database is a persistence library that provides an abstraction ...read more

Job scheduler is a component in Android that allows you to schedule tasks to be run at specified times or intervals.

• Job scheduler is used to schedule background tasks that need to be run periodically or under certain conditions.

• It helps in optimizing battery life by grouping tasks and running them when the device is idle.

• You can set constraints like network availability, charging status, and device idle state for the scheduled tasks.

• Job scheduler is more efficient than using ...read more

Services are used in Android to perform long-running operations in the background without affecting the user interface.

• Services help in running tasks in the background even when the app is not in the foreground.

• They can be used for tasks like playing music, downloading files, or fetching data from a server.

• Services can be started or bound to activities based on the requirements of the app.

OOPs stands for Object-Oriented Programming. It is based on four main pillars: Inheritance, Encapsulation, Abstraction, and Polymorphism.

• Inheritance: Allows a class to inherit properties and behavior from another class. Example: class B extends class A.

• Encapsulation: Bundling data and methods that operate on the data into a single unit. Example: using private access modifiers to restrict access to certain data.

• Abstraction: Hiding the complex implementation details and showing...read more

Back stack is a stack of activities in Android that keeps track of the navigation history.

• Back stack is managed by the Android system to handle the navigation flow of activities.

• When a new activity is started, it is pushed onto the back stack.

• Pressing the back button pops the top activity off the stack and navigates to the previous activity.

• Activities in the back stack can be brought to the foreground by using the appropriate navigation methods.

Databinding is a feature that allows you to bind UI components in your layout to data sources in your app.

• Databinding eliminates the need for boilerplate code to update UI components with data.

• It allows for easier communication between UI components and data sources.

• Databinding can improve code readability and maintainability.

• Example: Binding a TextView directly to a ViewModel property in an Android app.

OOPs (Object-Oriented Programming) is a programming paradigm based on the concept of objects, which can contain data in the form of fields and code in the form of procedures.

• OOPs focuses on creating objects that interact with each other to solve a problem.

• It involves concepts like inheritance, encapsulation, polymorphism, and abstraction.

• Inheritance allows a class to inherit properties and behavior from another class.

• Encapsulation involves bundling data and methods that opera...read more