10+ Senior Android Application Developer Interview Questions and Answers

The interview questions cover various topics related to Android development, including activity and fragment life cycle, communication between fragments, MVVM design pattern, Kotlin modifiers, abstract vs interface, coroutines, background services, and Room database implementation.

• Understand the life cycle of activities and fragments in Android development

• Use communication techniques like interfaces or shared view models to communicate between parent and child fragments

• Implem...read more

Program to find duplicate words and their frequency in a given string.

• Split the string into an array of words

• Create a hashmap to store word frequency

• Iterate through the array and update the hashmap

• Print the words with frequency greater than 1

Reverse a string and demonstrate safe call and null check operator in Kotlin

• To reverse a string in Kotlin, you can use the built-in extension function 'reversed()'

• Safe call operator '?' is used to safely access properties of nullable objects without causing NullPointerException

• Null check operator '!!' is used to explicitly throw a NullPointerException if a nullable object is null

Develop an Android app for weather forecasting using dependency injection for better code management and testing.

• Use Retrofit for API calls to fetch weather data from a service like OpenWeatherMap.

• Implement Dagger or Hilt for dependency injection to manage instances of API services and repositories.

• Create a ViewModel to handle UI-related data in a lifecycle-conscious way.

• Use LiveData to observe weather data changes and update the UI accordingly.

• Design a simple UI with Recycle...read more

Activity life cycle is a crucial concept in Android development. Factorial and Fibonacci series are common mathematical problems. lateinit var and lazy are used for initializing variables. Var and val are used for declaring variables.

• Activity life cycle includes methods like onCreate, onStart, onResume, onPause, onStop, onDestroy.

• Factorial is the product of all positive integers up to a given number. Example: 5! = 5*4*3*2*1 = 120.

• Fibonacci series is a sequence where each numb...read more

Sensitive data should be stored securely using encryption and secure storage mechanisms.

• Use encryption algorithms like AES to encrypt sensitive data before storing it in the database.

• Store encryption keys securely, separate from the data they encrypt.

• Implement secure storage mechanisms like Android Keystore to protect sensitive data.

• Avoid storing sensitive data in plain text or easily accessible formats.

Keystore file is a secure container used to store cryptographic keys and certificates for Android applications.

• Keystore file is used to securely store private keys, public keys, and certificates used for encryption and authentication in Android applications.

• It helps in protecting sensitive information such as passwords, API keys, and other credentials.

• Keystore file can be generated using keytool command-line utility or Android Studio.

• It is important to keep the keystore file ...read more

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

• ViewModel survives configuration changes such as screen rotations.

• ViewModel is not destroyed when an activity is destroyed and recreated.

• ViewModel is typically used to hold and manage data for UI components such as activities and fragments.

SOLID is a set of five principles in object-oriented programming to make software designs more understandable, flexible, and maintainable.

• S - Single Responsibility Principle: A class should have only one reason to change.

• O - Open/Closed Principle: Software entities should be open for extension but closed for modification.

• L - Liskov Substitution Principle: Objects of a superclass should be replaceable with objects of its subclasses without affecting the functionality.

• I - Inter...read more

StateHoist is a library in Android development used for managing the lifecycle of Android components.

• StateHoist helps in handling configuration changes and other lifecycle events in Android apps.

• It simplifies the process of saving and restoring instance state of activities and fragments.

• StateHoist can be used to retain data across configuration changes, such as screen rotations.

• It provides a convenient way to manage the lifecycle of Android components without boilerplate code...read more

var is mutable and can be reassigned, val is immutable and cannot be reassigned.

• var can be reassigned with a new value, val cannot be reassigned once initialized

• var is mutable, val is immutable

• Example: var number = 5; number = 10; // valid, val number = 5; number = 10; // invalid

Collections in Android are data structures that store and manage groups of objects.

• Collections provide methods to add, remove, and manipulate objects in a group.

• Examples of collections in Android include ArrayList, LinkedList, and HashMap.

• Collections can be used to efficiently store and retrieve data in Android applications.

The Android Activity lifecycle manages the states of an Activity, ensuring efficient resource use and user experience.

• onCreate(): Initializes the Activity, called when the Activity is first created. Example: setContentView(R.layout.activity_main);

• onStart(): Called when the Activity becomes visible to the user. Example: Start animations or refresh UI.

• onResume(): Called when the Activity starts interacting with the user. Example: Resume paused tasks like video playback.

• onPause(...read more

Kotlin is a modern programming language that is concise, expressive, and fully interoperable with Java.

• Kotlin is statically typed and supports both object-oriented and functional programming.

• It has features like null safety, extension functions, coroutines, and smart casts.

• Kotlin is officially supported for Android development by Google.