Mobile & App Development Interview Questions & Answers

Native development uses platform-specific languages (Swift/Kotlin), hybrid uses web technologies, and cross-platform uses frameworks like React Native or Flutter to create apps for multiple platforms with a single codebase.

The lifecycle includes requirement analysis, design, development, testing, deployment, maintenance, and updates. It involves planning, prototyping, coding, quality assurance, and continuous improvement.

The two primary mobile operating systems are Android (Google) and iOS (Apple), which together account for over 99% of the global mobile operating system market.

Key skills include programming languages (Java/Kotlin/Swift), understanding of mobile UI/UX design, API integration, database management, version control, and knowledge of platform-specific guidelines.

Android uses Android Studio with Kotlin/Java and supports multiple device manufacturers. iOS uses Xcode with Swift/Objective-C and is limited to Apple devices, offering more controlled development environment.

Challenges include device fragmentation, varying screen sizes, performance optimization, platform-specific design guidelines, security concerns, and keeping up with rapidly evolving technologies.

Responsive design ensures apps adapt to different screen sizes, orientations, and device capabilities by using flexible layouts, scalable images, and adaptive UI components.

PWAs are web applications that provide a native app-like experience using web technologies, offering features like offline functionality, push notifications, and device hardware access.

Monetization strategies include in-app purchases, subscription models, advertising, freemium models, paid apps, and sponsored content/partnerships.

Emerging technologies include AI/ML integration, augmented reality (AR), blockchain, Internet of Things (IoT) connectivity, and advanced machine learning frameworks.

Kotlin offers more concise syntax, null safety, extension functions, coroutines for async programming, and full Java interoperability, while reducing boilerplate code compared to Java.

The Android activity lifecycle includes states: onCreate(), onStart(), onResume(), onPause(), onStop(), onDestroy(), with methods handling initialization, running, pausing, and terminating app components.

The Android Manifest.xml declares app components, permissions, hardware/software requirements, and provides essential information to the Android system about the app's structure and functionality.

Background processing can be achieved using Services, WorkManager, AsyncTask, Coroutines, Threads, and background services, each suitable for different scenarios like long-running tasks or periodic work.

Dependency injection is a design pattern where dependencies are provided externally, reducing tight coupling. Libraries like Dagger and Hilt help manage dependencies and improve code modularity.

Jetpack Compose is a modern UI toolkit for Android that simplifies and accelerates UI development using a declarative approach, reducing XML layouts and offering more reactive and composable UI components.

Data persistence methods include SharedPreferences for key-value storage, SQLite databases, Room persistence library, File storage, and external storage solutions like Firebase Realtime Database.

RecyclerView is more efficient and flexible, supporting complex layouts, view recycling, animations, and dynamic item changes, whereas ListView is older and has limited customization options.

Intents are messaging objects used to request actions between components. Types include Explicit Intents (specific component targeting) and Implicit Intents (declaring a general action to be performed).

Key architecture components include ViewModel for managing UI-related data, LiveData for observable data, Room for database abstraction, and Lifecycle-aware components for managing app lifecycle.

Swift offers type safety, optionals, functional programming features, and modern syntax, while Objective-C is more verbose, dynamically typed, and has legacy support in older iOS codebases.

The iOS app lifecycle includes methods like application(_:didFinishLaunchingWithOptions:), applicationWillResignActive(), applicationDidEnterBackground(), covering app initialization, foreground/background transitions, and termination.

Storyboards provide a visual representation of app screens and their connections, allowing developers to design UI flow, define segues between view controllers, and manage app navigation.

Closures are self-contained blocks of functionality that can be passed around and used in code, similar to anonymous functions, enabling more concise and functional programming patterns.

Protocol-Oriented Programming emphasizes defining protocols with default implementations, promoting composition over inheritance, and enabling more flexible and modular code design.

iOS concurrency methods include Grand Central Dispatch (GCD), Operation Queues, async/await syntax in Swift, completion handlers, and actors for managing shared mutable state.

Core Data is an object graph and persistence framework that manages an object's lifecycle, provides data storage, retrieval, and supports features like undo/redo and relationship management.

Combine is a declarative Swift framework for processing values over time, enabling reactive programming by providing a unified approach to handle asynchronous events and data streams.

Property wrappers allow custom behavior for property storage, such as @State for SwiftUI views, @Published for observable objects, and @Wrapper for custom property management.

Extensions allow adding new functionality to existing types without modifying their original source code, enabling method, property, and protocol conformance additions to classes, structs, and enums.

Key principles include simplicity, consistency, user-centered design, intuitive navigation, responsive layouts, accessibility, visual hierarchy, and minimizing user cognitive load.

UI (User Interface) focuses on visual elements and interactions, while UX (User Experience) encompasses the overall user journey, emotions, and satisfaction with the entire app experience.

Android follows Material Design with card-based layouts and depth effects, while iOS uses Human Interface Guidelines emphasizing minimalism, translucency, and depth through layering.

Responsive design ensures apps adapt to different screen sizes, orientations, and device capabilities using flexible layouts, scalable images, and adaptive UI components.

Accessibility involves supporting screen readers, providing alternative text, ensuring sufficient color contrast, supporting dynamic type, enabling voice control, and designing for users with diverse abilities.

Design patterns include singleton, factory, observer, and model-view-controller (MVC), providing reusable solutions to common design problems and improving code organization.

Micro-interactions are subtle animations and feedback mechanisms that enhance user engagement, provide system status updates, and create a more intuitive and delightful user experience.

Strategies include using constraint-based layouts, adaptive and responsive design techniques, providing alternative layouts for different screen sizes, and testing across multiple device configurations.

Best practices include using familiar navigation patterns, providing clear hierarchies, minimizing taps, using bottom navigation, implementing search functionality, and ensuring intuitive back navigation.

Color psychology involves using colors to evoke emotions, guide user attention, establish brand identity, create visual hierarchy, and influence user perception and interaction with the app.

MVC separates an application into three interconnected components: Model (data), View (UI), and Controller (logic), promoting separation of concerns and modular code organization.

MVVM separates UI logic from business logic by introducing a ViewModel that transforms Model data for View presentation, enabling better testability and maintainability.

MVC has a direct controller-view relationship, while MVVM uses data binding and observables, offering more flexible and testable code with reduced coupling between components.

Clean architecture promotes separation of concerns, dependency inversion, testability, and scalability by organizing code into independent layers with clear responsibilities.

Dependency injection is a design pattern where dependencies are provided externally, reducing tight coupling, improving modularity, and facilitating easier testing and maintenance.

The repository pattern abstracts data source interactions, providing a consistent interface for data access, centralizing data management, and enabling easier switching between local and remote data sources.

Unidirectional data flow ensures data moves in a single direction, reducing complexity, making state changes predictable, and simplifying debugging in large-scale applications.

Considerations include modular design, loose coupling, dependency injection, separation of concerns, performance optimization, and supporting future feature expansions.

Use cases encapsulate business logic, representing specific application interactions, promoting single responsibility and making core application logic independent of frameworks and UI.

Reactive programming focuses on data streams and change propagation, enabling more declarative and event-driven application designs with frameworks like RxJava and Combine.

Common methods include REST APIs, GraphQL, WebSocket connections, using libraries like Retrofit (Android), Alamofire (iOS), and implementing URLSession or HttpClient for network requests.

JSON parsing converts JSON data to native objects, enabling efficient data transfer between client and server. Libraries like Gson, Moshi, and Codable help simplify this process.

Best practices include implementing proper error handling, using background threads, caching responses, managing request timeouts, providing user feedback, and handling network connectivity changes.

OAuth 2.0 is an authorization framework enabling third-party applications to access user resources without exposing credentials, commonly used for secure social media and service integrations.

Offline synchronization involves caching data locally, tracking changes, implementing conflict resolution strategies, and using techniques like background sync and queue-based updates.

GraphQL is a query language allowing clients to request specific data, offering more flexibility and efficiency compared to REST by reducing over-fetching and under-fetching of data.

Serialization converts complex objects to a storable/transmittable format, while deserialization reconstructs objects from that format, crucial for data persistence and network communication.

WebSockets provide full-duplex, real-time communication between client and server, enabling instant updates and more efficient communication compared to traditional HTTP requests.

Data binding automatically synchronizes UI elements with underlying data models, reducing boilerplate code and ensuring consistent UI representation across different app states.

Robust error handling involves catching network errors, providing user-friendly error messages, implementing retry mechanisms, logging errors, and gracefully managing different error scenarios.

Primary threats include data breaches, reverse engineering, man-in-the-middle attacks, insecure data storage, code injection, unauthorized access, and malware/tampering risks.

Secure storage involves using encrypted databases, keychain services, secure shared preferences, avoiding storing sensitive data locally, and implementing proper access controls.

Certificate pinning prevents man-in-the-middle attacks by hardcoding trusted SSL certificates, ensuring apps only communicate with specific servers and rejecting unauthorized certificates.

Best practices include using multi-factor authentication, implementing secure token management, protecting against brute-force attacks, and supporting biometric authentication methods.

Protection techniques include code obfuscation, using ProGuard/R8 for Android, implementing anti-tampering mechanisms, encryption, and avoiding storing sensitive logic client-side.

Considerations include using HTTPS, implementing proper authentication, validating and sanitizing input data, rate limiting, and protecting against common web vulnerabilities like CSRF and XSS.

Secure dependency management involves regularly updating libraries, checking for known vulnerabilities, using trusted sources, and conducting security audits of third-party components.

RASP provides real-time security by detecting and preventing runtime attacks, monitoring application behavior, and automatically responding to potential security threats.

Best practices include requesting minimal necessary permissions, providing clear permission rationales, implementing runtime permission requests, and respecting user privacy preferences.

Secure local storage involves using encryption, secure enclaves, keychain services, avoiding storing sensitive data in plain text, and implementing proper access controls.

Strategies include efficient memory management, minimizing network requests, optimizing UI rendering, using background threads, implementing lazy loading, and reducing app size.

Memory management involves preventing memory leaks, using weak references, implementing proper object lifecycle management, and avoiding unnecessary object creation and retention.

UI rendering optimization includes using efficient layout hierarchies, avoiding complex view nesting, implementing view recycling, using hardware acceleration, and minimizing overdraw.

Techniques include implementing request caching, using efficient serialization, minimizing payload size, compressing data, batching requests, and implementing intelligent prefetching.

Best practices involve using background services, WorkManager, coroutines, thread pools, avoiding blocking main threads, and implementing efficient task scheduling.

Lazy loading delays object initialization until necessary, reducing initial memory consumption, improving startup time, and optimizing resource utilization in mobile applications.

Effective caching involves using in-memory and disk caches, implementing cache invalidation strategies, setting appropriate cache sizes, and managing cache lifecycles.

Profiling tools include Android Profiler, Xcode Instruments, LeakCanary, Firebase Performance Monitoring, and platform-specific performance analysis frameworks.

Considerations include using vector graphics, implementing code shrinking, removing unused resources, using app bundles, and optimizing image and asset sizes.

Asynchronous programming prevents blocking the main thread, enables responsive UIs, improves app performance, and facilitates efficient handling of time-consuming operations.

Key steps include thoroughly testing the app, optimizing performance, implementing proper error handling, ensuring compliance with store guidelines, preparing screenshots and metadata, and creating a compelling app description.

The submission process involves creating a developer account, preparing app bundle/APK, configuring store listing, setting pricing, providing screenshots, adding descriptions, and going through Google's review process.

Apple's guidelines include strict UI/UX requirements, privacy considerations, performance standards, content restrictions, mandatory app review process, and adherence to human interface guidelines.

Common rejection reasons include poor performance, incomplete functionality, security vulnerabilities, inappropriate content, lack of user value, privacy policy violations, and non-compliance with platform guidelines.

CI/CD involves using tools like Jenkins, GitLab CI, GitHub Actions, and platform-specific solutions to automate building, testing, and deployment processes for mobile applications.

Versioning involves incrementing version codes/numbers, maintaining semantic versioning, providing changelog information, implementing automatic updates, and managing backward compatibility.

Considerations include choosing between free, paid, and freemium models, implementing in-app purchases, managing subscriptions, integrating advertising, and complying with store policies.

ASO involves optimizing app title, keywords, description, screenshots, and icons to improve visibility, increase downloads, and rank higher in app store search results.

Analytics involve using tools like Firebase, Google Analytics, Crashlytics, and custom tracking to monitor user engagement, performance metrics, crash reports, and user behavior.

Requirements include providing clear privacy policies, obtaining user consent for data collection, implementing data protection measures, supporting user data deletion, and complying with GDPR and CCPA regulations.