100+ Senior Android Developer Interview Questions and Answers

Yes, the binary array sorting problem can be solved in linear time and constant space by using a two-pointer approach.

• Use two pointers, one starting from the beginning of the array and the other starting from the end.

• Swap 0s to the left side and 1s to the right side by incrementing and decrementing the pointers accordingly.

• Continue this process until the two pointers meet in the middle of the array.

• Example: Input: [1, 0, 1, 0, 1], Output: [0, 0, 1, 1, 1]

Find the sum of the subarray with the maximum sum among all subarrays in a given array.

• Iterate through the array and keep track of the maximum sum subarray encountered so far.

• Use Kadane's algorithm to efficiently find the maximum subarray sum.

• Consider the case where all elements in the array are negative.

• Handle the case where the array contains only one element.

Questions related to Android development concepts and practices.

• Daemon thread is a low priority thread that runs in the background.

• Data class is a class that is used to hold data and provides default implementations of common methods like equals, hashCode, and toString.

• Garbage collector is a mechanism that automatically frees up memory by removing objects that are no longer in use.

• Activity lifecycle refers to the various states an activity can be in, such as onCreate, onStart...read more

A Service is a component that runs in the background to perform long-running operations. A Foreground Service is a Service that has a notification to show the user that it is running.

• A Service is used to perform long-running operations in the background, such as playing music in a music player app.

• A Foreground Service is a type of Service that has a notification to indicate to the user that it is running and to give it higher priority, making it less likely to be killed by th...read more

The data structure used to store views in a layout is a tree structure.

• Views in a layout are stored in a hierarchical tree structure.

• Each view is a node in the tree, with parent-child relationships defining the layout.

• Examples include LinearLayout, RelativeLayout, and ConstraintLayout.

Activity, service, view model, live data, and Jetpack Compose are key components in Android development.

• Activity: Represents a single screen with a user interface. Example: MainActivity.

• Service: Performs long-running operations in the background without a user interface. Example: MusicPlayerService.

• View Model: Stores and manages UI-related data in a lifecycle-conscious way. Example: MainViewModel.

• Live Data: Data holder class that is lifecycle-aware and ensures UI updates only...read more

Answers to various technical questions related to Android development.

• 1. When an app is launched on Android, the system creates a new instance of the Activity class for the main activity and loads the layout.

• 2. MVVM (Model-View-ViewModel) is a design pattern that separates the UI, business logic, and data. The View interacts with the ViewModel to update the data.

• 3. For a 2-page app with a listing and detail page, you can design a navigation flow using activities or fragments....read more

Questions on data structure, algorithm, and Android development.

• To find maximum sum subarray, use Kadane's algorithm

• To separate zeroes and ones in array, use two pointers approach

• ViewModel is a class that stores and manages UI-related data

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

• To implement ViewModel, extend ViewModel class and override onCleared() method

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

• RecyclerView recycles views to improve performance and memory usage.

• It uses a LayoutManager to organize and position items within the view.

• Adapter provides data to be displayed in the RecyclerView.

• ItemDecoration allows for custom drawing of item decorations like borders or dividers.

To recover uninstall rate of an android app, analyze user feedback, improve app performance, and offer incentives.

• Analyze user feedback to identify reasons for uninstallation

• Improve app performance to reduce crashes and bugs

• Offer incentives such as discounts or exclusive content to encourage reinstallation

Firebase is a mobile and web application development platform developed by Google. FCM is Firebase Cloud Messaging, a messaging service for Android, iOS, and web applications.

• Firebase provides a range of services including authentication, real-time database, cloud storage, and hosting.

• FCM allows developers to send notifications and messages to users on Android, iOS, and web applications.

• To integrate FCM, developers need to add the Firebase SDK to their app and configure the F...read more

Print prime numbers between 100 to 1,00,000

• Start with a loop from 100 to 100000

• Check if the current number is prime or not

• If prime, print the number

Using dependency injection in Android development can improve code maintainability and testability.

• Pros: easier to manage dependencies, promotes code reusability, facilitates unit testing

• Cons: initial setup can be complex, may introduce overhead in smaller projects

• Example: Using Dagger 2 for dependency injection in an Android project

The output of the program when 0 is divided by 7 is 0.

• Division of 0 by any number results in 0.

• In programming languages, dividing by 0 usually results in an error or undefined behavior.

Find largest subarray with equal number of 1s and 0s

• Use a hashmap to store the count of 1s and 0s encountered so far

• If the count of 1s and 0s is equal at any point, calculate the length of subarray

• Keep track of the maximum length subarray found so far

To detect loop in linked list, use Floyd's cycle-finding algorithm.

• Create two pointers, slow and fast, and initialize both to the head of the linked list.

• Move slow pointer by one node and fast pointer by two nodes.

• If there is a loop, the two pointers will eventually meet.

• If there is no loop, the fast pointer will reach the end of the linked list.

• Time complexity: O(n), Space complexity: O(1)

ConstraintLayout is preferred for its flexibility, efficiency, and ease of use in creating complex layouts.

• Allows for creating complex layouts with a flat view hierarchy, improving performance

• Supports responsive design with constraints that adapt to different screen sizes

• Easier to use and understand compared to other layout options like RelativeLayout

• Provides tools like Layout Editor in Android Studio for visual editing of layouts

Work manager is an Android library that manages background tasks efficiently.

• Work manager is part of Android Jetpack and is used for deferrable background tasks.

• It provides a way to schedule tasks that need to run even if the app is in the background or not running.

• Work manager handles task constraints, retries, and backoff policies automatically.

• Tasks can be one-time or periodic, with support for specifying constraints like network availability or charging status.

• Example: Wo...read more

Threads in Java allow for concurrent execution of code, enabling multitasking and improving performance.

• Threads are lightweight sub-processes within a process.

• They allow for concurrent execution of code, enabling multitasking.

• Threads share the same memory space, allowing for efficient communication and data sharing.

• Examples include creating threads using the Thread class or implementing the Runnable interface.

Content providers are components in Android that manage access to a structured set of data. They are used to share data between apps.

• Content providers allow apps to securely share data with other apps

• They provide a standard interface for querying and modifying data

• Content providers are often used to access data from databases or files

• Examples include the Contacts Provider for accessing contact information and the Media Provider for accessing media files

Coroutines, scope functions, and visibility modifiers are key concepts in Kotlin programming for Android development.

• Coroutines are a way to perform asynchronous programming in a sequential manner. They allow for non-blocking operations.

• Scope functions are functions that allow you to execute a block of code within the context of an object. Examples include 'let', 'apply', 'run', 'also', and 'with'.

• Visibility modifiers control the visibility of classes, interfaces, functions, ...read more

MVVM is an architectural pattern that separates the user interface from the business logic and data handling in Android development.

• Model represents the data and business logic of the application.

• View is responsible for displaying the UI elements and sending user interactions to the ViewModel.

• ViewModel acts as a mediator between the Model and the View, handling the communication and data flow.

• MVVM helps in achieving separation of concerns, making code more modular and easier ...read more

The root class in Java is the Object class, which is the parent class for all other classes in Java.

• The Object class is used to provide common methods and behaviors that are inherited by all other classes.

• It defines methods like toString(), equals(), and hashCode() that can be overridden by subclasses.

• All classes in Java implicitly extend the Object class, either directly or indirectly.

• For example, the String class extends the Object class.

The Android application components used in the previous project include activities, services, broadcast receivers, and content providers.

• Activities: Used for the user interface and interaction with the user. Example: MainActivity.java

• Services: Used for background tasks or long-running operations. Example: DownloadService.java

• Broadcast Receivers: Used for system-wide events or notifications. Example: ConnectivityReceiver.java

• Content Providers: Used for data management and shar...read more

Authentication is the process of verifying the identity of a user, while authorization is the process of granting access to specific resources.

• Authentication ensures that the user is who they claim to be, usually through credentials like username and password.

• Authorization determines what actions a user is allowed to perform on a system or resource.

• Coroutines are lightweight threads that allow for asynchronous programming in a more sequential and structured manner.

• Coroutines ...read more

Push notification is a message that pops up on a mobile device. It can be implemented in Android using Firebase Cloud Messaging (FCM) or Google Cloud Messaging (GCM).

• Push notifications are messages sent from a server to a client app that wakes up the app to inform the user of new messages or events.

• In Android, push notifications can be implemented using Firebase Cloud Messaging (FCM) or Google Cloud Messaging (GCM) APIs.

• Developers need to set up a server to send push notifica...read more

The search page of a video streaming app should allow users to easily search for and discover content.

• Include a search bar at the top for users to enter keywords or phrases

• Display relevant search results in a grid or list format

• Provide filters or sorting options to refine search results

• Include thumbnails, titles, and brief descriptions of the search results

• Allow users to click on search results to view more details or start streaming

Flow is a cold asynchronous data stream, Channel is a hot asynchronous data stream. StateFlow is a hot asynchronous data stream with a state, SharedFlow is a hot asynchronous data stream without a state.

• Flow is a cold asynchronous data stream that emits values one by one.

• Channel is a hot asynchronous data stream that can have multiple subscribers.

• StateFlow is a hot asynchronous data stream that retains the most recent value and emits it to new subscribers.

• SharedFlow is a hot ...read more

MVC, MVP, MVVM are design patterns for organizing code. Glide and Picasso are image loading libraries. Bitmap sampling is resizing images. ViewStub is a lightweight view. RecyclerView can achieve fixed size with setHasFixedSize(true). Inline functions are defined within a class. WorkManager can schedule background tasks.

• MVC, MVP, MVVM are design patterns for organizing code

• Glide and Picasso are popular image loading libraries

• Bitmap sampling is resizing images to reduce memory...read more

Volatile keyword ensures visibility of changes to variables across threads. Reified keyword is used to access type information at runtime in generics.

• Volatile keyword is used to indicate that a variable's value will be modified by different threads.

• It ensures that changes made by one thread to a volatile variable are visible to other threads.

• Reified keyword is used in generics to access type information at runtime, which is not possible with regular generics due to type erasu...read more

Kotlin extension functions allow adding new functions to existing classes without modifying their source code.

• Extension functions are defined outside the class they extend.

• They can be called on the object of the class they extend.

• They can access the properties and functions of the class they extend.

Multiple views in RecyclerView can be handled by using different view types and view holders.

• Use getItemViewType() method to return different view types based on position

• Create multiple view holders for each view type

• Bind data to each view holder based on its type

• Example: Creating a chat app with different message types like text, image, and video

Different types of interfaces include user interfaces, hardware interfaces, and software interfaces.

• User interfaces: allow users to interact with the system, such as graphical user interfaces (GUI) and command-line interfaces (CLI)

• Hardware interfaces: connect hardware components to the system, such as USB, HDMI, and Ethernet ports

• Software interfaces: define how software components interact with each other, such as application programming interfaces (APIs) and network protocol...read more

Inline functions are functions that are expanded in place at the call site, while high-order functions are functions that can take other functions as parameters or return them.

• Inline functions are expanded in place at the call site to improve performance.

• High-order functions can take other functions as parameters or return them.

• Example of high-order function: map() function in Kotlin.

I solved a problem by implementing a custom view to display complex data in a more user-friendly way.

• Identified the specific requirements and limitations of the problem

• Researched and experimented with different solutions, including using third-party libraries

• Implemented a custom view with optimized performance and user experience

• Tested the solution thoroughly to ensure it met the desired functionality

Service is a base class for Android services that can run in the background, while IntentService is a subclass of Service that handles asynchronous requests on demand.

• Service is a base class for Android services that can run indefinitely in the background, while IntentService is a subclass of Service that handles asynchronous requests one at a time.

• Service does not have a default worker thread, so you need to manage the thread manually, whereas IntentService creates a worker ...read more

Car propertymanager is a component in AOSP that manages properties related to car-specific features.

• Car propertymanager is used to handle properties like car make, model, year, etc.

• It is mostly used in Android Automotive OS for managing car-specific settings and configurations.

• Developers can use car propertymanager to access and modify car-related properties in their apps.

Coroutines are a concurrency design pattern in Kotlin that allow for asynchronous programming.

• Coroutines are lightweight threads that can be used to perform non-blocking operations.

• They are based on the concept of suspending functions, which can be paused and resumed.

• Coroutines use a dispatcher to determine which thread or thread pool to run on.

• They can be used to simplify asynchronous code and avoid callback hell.

• Coroutines can be used with various libraries and frameworks, ...read more

FnO stands for Futures and Options, a type of financial derivative. Implemented feature by integrating real-time market data and enabling users to trade contracts.

• FnO is a type of financial derivative where parties agree to buy or sell an asset at a specified price on a future date.

• Implemented feature by integrating real-time market data feeds to provide up-to-date information on contract prices.

• Enabled users to trade futures and options contracts through the app, with featur...read more

Multi module architecture in Android involves breaking down an app into multiple modules for better organization and scalability.

• Pros: better organization, easier maintenance, faster build times, code reusability

• Cons: increased complexity, potential for dependency issues, learning curve for developers

• Example: Breaking down an app into separate modules for UI, networking, and data storage can make it easier to work on different parts of the app independently.

IPC stands for Inter-Process Communication and RPC stands for Remote Procedure Call.

• IPC is a mechanism that allows communication between processes running on the same or different devices.

• RPC is a protocol that enables one program to request a service from another program on a remote machine.

• IPC can be achieved through shared memory, message passing, and pipes.

• RPC uses a client-server model and can be implemented using various protocols such as HTTP, TCP, and UDP.

• Both IPC and...read more

Count pretty numbers ending with 2, 3, or 7 within a given range.

• Iterate through the range from x to y and check if each number ends with 2, 3, or 7.

• Increment a counter for each pretty number found.

• Return the total count of pretty numbers within the range.

Dispatchers in Kotlin Coroutines are responsible for determining which thread or threads the coroutines should run on.

• Dispatchers help manage the execution of coroutines on different threads.

• There are different types of Dispatchers like Default, IO, Main, and Unconfined.

• Example: launch(Dispatchers.IO) { // perform network operations }

Design a feature for an app

• Identify the purpose and goals of the feature

• Define the user flow and interactions

• Consider the technical requirements and constraints

• Design the UI/UX

• Plan the data model and storage

• Consider scalability and performance

• Implement and test the feature

MVVM is a design pattern that separates the UI, business logic, and data layers in Android development.

• MVVM stands for Model-View-ViewModel.

• Model represents the data and business logic.

• View is the UI component that displays the data and interacts with the user.

• ViewModel acts as a mediator between the Model and View, handling data operations and updating the UI.

• Other architectures used in Android include MVP (Model-View-Presenter) and MVC (Model-View-Controller).

Different launch modes in Android control how a new instance of an activity is associated with the current task.

• Standard - The default launch mode, creates a new instance of the activity in the task.

• SingleTop - If an instance of the activity already exists at the top of the task, it will not be recreated.

• SingleTask - A new task will always be created and a new instance of the activity will be launched in it.

• SingleInstance - The activity will be the only one in the task, no ot...read more

To find the middle of a linked list, use the slow and fast pointer technique.

• Initialize two pointers, slow and fast, at the head of the linked list.

• Move the slow pointer by one node and the fast pointer by two nodes until the fast pointer reaches the end of the list.

• The node pointed to by the slow pointer at this point is the middle of the linked list.