80+ Android Developer Interview Questions and Answers for Freshers

Create a BSTIterator class for inorder traversal of a binary search tree.

• Implement a constructor that takes the root of the binary search tree and initializes the iterator.

• Implement next() function to return the next smallest element in the inorder traversal.

• Implement hasNext() function to check if there is a next element in the inorder traversal.

• Traverse the binary search tree in inorder to get the desired output.

The problem involves finding the number of ways to express a given positive integer as a sum of cubes of two integers.

• Iterate through all possible values of A and B within the given constraints.

• Check if A^3 + B^3 equals the given N, increment the count if true.

• Handle the case where A = B separately to avoid counting duplicates.

The Colorful Knapsack Problem involves selecting one stone of each color to fill a knapsack with a given weight capacity, minimizing unused capacity.

• Iterate through the stones and keep track of the minimum weight for each color.

• Use dynamic programming to find the optimal solution by considering all possible combinations.

• Handle cases where the knapsack cannot be filled under the given conditions by returning -1.

• In the given example, the optimal solution is to select stones wit...read more

Convert an integer to its corresponding Roman numeral representation.

• Create a mapping of integer values to Roman numeral symbols.

• Iterate through the mapping in descending order of values and build the Roman numeral representation.

• Subtract the largest possible value from the integer at each step and append the corresponding Roman numeral symbol.

• Repeat until the integer becomes 0.

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);

Minimum time required to cross the bridge is 17 minutes.

• A and B cross (2 minutes), A returns (1 minute), C and D cross (10 minutes), B returns (2 minutes), A and B cross (2 minutes).

• Always send the fastest person back to minimize time.

• Total time taken is the sum of all individual crossing times.

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.

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.

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

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

Interfaces define a contract for classes, while abstract classes provide a base with shared code and can have state.

• An interface can only declare methods (no implementation) while an abstract class can have both abstract and concrete methods.

• A class can implement multiple interfaces but can inherit from only one abstract class.

• Interfaces are used for defining capabilities (like Comparable), while abstract classes are used for shared behavior.

• Example: 'interface Drawable { voi...read more

To find a missing element in an array, iterate through the array and compare each element with a range of expected values.

• Sort the array if it is unsorted.

• Iterate through the array and compare each element with a range of expected values.

• If an element is missing, return it.

• If no element is missing, return null or -1.

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.

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().

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

MVVM is a software architectural pattern that separates UI logic from business logic, enhancing testability and maintainability.

• Model: Represents the data and business logic. Example: A class that fetches user data from a database.

• View: The UI layer that displays data. Example: An XML layout file in Android that shows user information.

• ViewModel: Acts as a bridge between Model and View, holding UI-related data. Example: A ViewModel that prepares user data for the View.

• Data Bin...read more

Kotlin coroutines simplify asynchronous programming by allowing non-blocking code execution with structured concurrency.

• Types of coroutines: Launch, Async, and RunBlocking.

• Launch: Starts a coroutine without blocking the current thread. Example: CoroutineScope.launch { /* code */ }

• Async: Starts a coroutine and returns a Deferred result. Example: val result = CoroutineScope.async { /* code */ }

• RunBlocking: Blocks the current thread until the coroutine completes. Example: runBlo...read more

Jetpack Compose effects manage side effects in UI, ensuring a responsive and declarative approach to state changes.

• 1. LaunchedEffect: Used for launching coroutines tied to a composable's lifecycle. Example: `LaunchedEffect(key1) { /* Coroutine code */ }`.

• 2. rememberCoroutineScope: Provides a CoroutineScope tied to the composable's lifecycle. Example: `val scope = rememberCoroutineScope()`.

• 3. SideEffect: Executes code after the composition is applied. Example: `SideEffect { /*...read more

Use interfaces for contracts and multiple inheritance; use abstract classes for shared code and single inheritance.

• Interfaces define a contract that implementing classes must follow. Example: 'Runnable' interface in Java.

• Abstract classes can have both abstract methods (no implementation) and concrete methods (with implementation). Example: 'Activity' class in Android.

• Use interfaces when you want to allow multiple inheritance. A class can implement multiple interfaces.

• Use abst...read more

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.

Shift all zeroes in an array to the left while maintaining the order of non-zero elements.

• Iterate through the array and count non-zero elements.

• Use a new array to place non-zero elements first.

• Fill the remaining positions with zeroes.

• Example: For [0, 1, 0, 3, 12], result is [0, 0, 1, 3, 12].

• In-place approach: Use two pointers to swap elements.

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