Cross-Platform Mobile Development Flashcards

Question 1

What is the difference between an app's source code and its compiled binary?

Accepted Answer

Source code is the human-readable program a developer writes in a project, usually in a language such as Dart, Kotlin, Swift, or TypeScript. The compiler or build tool transforms it into a binary or bundle that a device can run or install. Cross-platform tools differ in how they produce output for each target.

Question 2

What does cross-platform mobile development mean, and why do teams choose it?

Accepted Answer

Cross-platform mobile development means writing application code once and running it on more than one mobile operating system, most often iOS and Android. Teams choose it to reduce duplicated work, shorten schedules, and keep features consistent across devices. The trade-off is that shared code must respect each platform's design conventions and performance limits.

Question 3

What is a native mobile app, and how does it differ from a shared codebase?

Accepted Answer

A native mobile app is written with the platform's own languages and toolkits, such as Swift for iOS and Kotlin for Android. Each platform gets separate code, which gives full access to system features. A shared codebase instead keeps most logic in one project that targets several platforms.

Question 4

What is a framework in the context of cross-platform development?

Accepted Answer

A cross-platform framework is a set of libraries, tools, and runtime components that lets developers build mobile apps for several operating systems with shared code. It usually provides its own project structure, build process, and ways to access device features. Choosing a framework means accepting its language, update cycle, and ecosystem.

Question 5

Why is a single codebase not the same as identical behavior on every device?

Accepted Answer

A single codebase guarantees that the source code is shared, but it does not guarantee that the app looks or behaves the same everywhere. Operating systems differ in permissions, navigation patterns, background limits, and screen behavior. Developers still write platform-specific code or configuration where those differences matter.

Question 6

What is the purpose of a shared business logic layer?

Accepted Answer

A shared business logic layer holds rules such as validation, calculations, and data handling in code that every platform can reuse. Keeping this logic separate from screens lets teams test it once and change interfaces without rewriting core behavior. Platform-specific code then focuses on presentation and device integration.

Question 7

What is a platform abstraction layer, and why do developers write one?

Accepted Answer

A platform abstraction layer is an interface that hides differences between operating systems behind one set of functions the shared code can call. Each platform supplies its own implementation, such as one for camera access on iOS and another on Android. This keeps application code unaware of which system it runs on.

Question 8

What is a device capability, and why does it matter in mobile development?

Accepted Answer

A device capability is a feature of the hardware or operating system that an app can use, such as the camera, GPS, accelerometer, Bluetooth, or push notifications. Access usually requires a permission that the user must grant, and each platform has its own rules for requesting it. Shared code must expose them consistently.

Question 9

What does it mean for an app's user interface to be rendered natively?

Accepted Answer

Rendering natively means the framework draws interface elements using the platform's own widgets or views, so buttons and lists look and behave like the operating system's. Some frameworks instead draw every pixel themselves, which keeps looks identical across devices but can feel less familiar. Developers weigh this choice carefully.

Question 10

What is a hybrid app, and how is it usually packaged?

Accepted Answer

A hybrid app is built with web technologies such as HTML, CSS, and JavaScript, then wrapped in a native shell that runs inside a web view on the device. The shell lets the app be installed from app stores and call some device features through plugins.

Question 11

How do progressive web apps differ from hybrid or native apps?

Accepted Answer

Progressive web apps are websites that use modern browser features such as service workers and web app manifests to behave like installed apps. They run in the browser rather than inside a packaged app shell, and they need no separate app store submission. Their access to device features varies by browser and operating system.

Question 12

What is a web view, and why does it matter for hybrid apps?

Accepted Answer

A web view is a component that displays web content inside a native application, using the platform's browser engine. Hybrid apps depend on it to render their screens, so performance, scrolling smoothness, and access to newer web features depend on the device's web view implementation. Its quality therefore varies across platforms.

Question 13

What are the main advantages of building a fully native app?

Accepted Answer

A fully native app uses each platform's own languages, tools, and interface components, which usually gives strong performance and direct access to system features. Developers receive new platform capabilities, and the app follows local design conventions closely. The cost is maintaining separate codebases and teams for each operating system.

Question 14

How does sharing logic while keeping native interfaces differ from sharing the whole interface?

Accepted Answer

Sharing logic while keeping native interfaces means common rules and data code is written once, but each platform builds its own screens with its usual toolkit. Sharing the whole interface means one set of components renders everywhere, which saves more effort but makes platform-specific polish harder.

Question 15

Why might a team choose a web-based approach for an internal tool?

Accepted Answer

A web-based approach can suit internal tools because one deployment reaches every device with a browser, and updates happen on the server without store review. Limited device access and offline support may still be constraints. Teams should weigh these factors against the expected user base and required hardware features.

Question 16

What are the main drawbacks of a hybrid approach?

Accepted Answer

Hybrid apps can feel less responsive than native apps, especially with complex animations, long lists, or heavy graphics. They also depend on web view behavior, which may differ between operating systems and versions. Debugging can involve both web tools and native tools, which adds complexity to the workflow.

Question 17

What is a declarative user interface, and why do many cross-platform frameworks use one?

Accepted Answer

A declarative user interface describes what the screen should look like for a given state, and the framework updates the display when that state changes. Many cross-platform frameworks use this model because it reduces manual screen updates and keeps the interface logic easier to follow. Flutter and React Native both follow this idea.

Question 18

What is the main purpose of a build system in mobile development?

Accepted Answer

A build system compiles source code, bundles resources such as images and fonts, and packages the result into an installable file for each target platform. In mobile projects it also handles signing, dependency resolution, and configuration for different build variants. Automating these steps makes releases more repeatable and reduces manual errors.

Question 19

What is a native module, and why do cross-platform frameworks use them?

Accepted Answer

A native module is platform code, written in the operating system's own language, that exposes a feature to shared code through a defined interface. Frameworks use them when no built-in component covers a needed capability, such as specialized sensors or vendor-specific SDKs. Developers then write each platform's side separately.

Question 20

What does a package manager do for a cross-platform project?

Accepted Answer

A package manager downloads, versions, and tracks third-party libraries that a project depends on. It records exact versions in a lock file so every developer and build server uses the same dependencies. This reduces surprises when a library updates and helps teams reproduce earlier builds reliably.

Question 21

Why do cross-platform projects often include separate folders for each platform's code?

Accepted Answer

Platform folders hold configuration and native code that cannot be expressed in the shared language, such as app icons, manifest files, signing settings, and permission declarations. Keeping them separate lets the shared code stay clean while each operating system receives the files it expects. Many teams review them during each release.

Question 22

What is hot reload, and why do developers value it?

Accepted Answer

Hot reload is a development feature that updates a running app with new code without restarting it or losing its current state. Developers value it because they can see interface and logic changes in seconds, which shortens the edit and test cycle. Some changes still require a full rebuild.

Question 23

What is a continuous integration pipeline, and how does it help cross-platform teams?

Accepted Answer

A continuous integration pipeline automatically builds and tests the project whenever code changes are submitted to the shared repository. For cross-platform teams, the pipeline can run builds for iOS and Android in parallel, catching platform-specific failures early. Early detection reduces the cost of fixing problems before release.

Question 24

How should a learner choose between frameworks for a new project?

Accepted Answer

A learner should compare frameworks against concrete project needs, such as required device features, performance targets, team skills, and the expected lifetime of the app. Reviewing each framework's documentation, community activity, and tooling helps reveal practical strengths and gaps. A small prototype built with two candidates often shows the trade-offs clearly than reading comparisons.

Question 25

What are platform conventions, and why do they matter in interface design?

Accepted Answer

Platform conventions are the common patterns users expect on a given operating system, such as navigation bars, back gestures, dialog styles, and placement of primary actions. Following them makes an app feel familiar and reduces the learning effort for new users. Ignoring them can make even a well-built app seem unpolished or confusing.

Question 26

How do responsive layouts help an app adapt to different screen sizes?

Accepted Answer

Responsive layouts arrange interface elements using flexible rules rather than fixed positions, so content resizes and reflows as the available space changes. Developers often use relative sizes, constraints, and breakpoints that switch arrangements at certain widths. This approach helps phones, tablets, and foldable devices show usable screens without separate designs for each model.

Question 27

What is safe area handling, and why do notched screens require it?

Accepted Answer

Safe area handling keeps important content away from regions that the hardware or operating system may obscure, such as camera cutouts, rounded corners, status bars, and home indicators. Apps that ignore these regions can place buttons or text where users cannot reliably tap or read them.

Question 28

Why should accessibility be considered from the start of a cross-platform project?

Accepted Answer

Accessibility features such as screen reader labels, sufficient color contrast, and logical focus order are easier to build in early than to retrofit later. Each platform exposes accessibility through its own APIs, so shared components must map to those interfaces. Testing with assistive technology on each target reveals problems automated checks often miss.

Question 29

What is a density-independent unit, and why should layouts avoid raw pixel values?

Accepted Answer

A density-independent unit, such as a dp on Android or a point on iOS, measures size in logical units that scale with the screen's pixel density. Raw pixel values look correct on one device but can appear too small or too large on another with a different density. Using logical units keeps text, spacing, and touch targets proportionate across phones and tablets.

Question 30

Why do navigation patterns differ between platforms, and how should apps respond?

Accepted Answer

Navigation patterns differ because each operating system has its own habits, such as tab bars, drawer menus, system back gestures, and hardware back buttons on some Android devices. Apps should respect the expected pattern for each platform while keeping the same underlying screens and routes. Shared navigation logic can drive different visual presentations.

Question 31

What is a design system, and how does it support consistent cross-platform interfaces?

Accepted Answer

A design system is a shared collection of reusable components, colors, typography, spacing rules, and usage guidelines. It helps teams keep screens consistent across platforms by defining each element once and documenting where platform variations are allowed. Systems also record which differences are intentional, so designers and developers can tell them apart from mistakes.

Question 32

How should an app handle dark mode across platforms?

Accepted Answer

An app should read the user's system appearance setting and apply matching color schemes. Colors should be defined as named tokens so light and dark variants stay consistent across screens. Contrast must be checked in both modes, because a palette that reads well in light mode can fail in dark mode.

Question 33

Why should a cross-platform project test on real devices and emulators?

Accepted Answer

Emulators and simulators are fast and convenient for early checks, but they cannot fully reproduce hardware behavior, sensor input, battery use, or manufacturer-specific quirks. Real devices reveal performance problems and platform differences that simulated environments may hide. A balanced strategy uses both, with real devices reserved for release candidates and tricky features.

Question 34

What is the difference between unit tests and end-to-end tests in a mobile project?

Accepted Answer

Unit tests check small pieces of logic in isolation, such as a price calculation or a validation rule, and run quickly. End-to-end tests drive the full app through its interface, like a user tapping through a login flow, and take longer to run. Both kinds catch different problems.

Question 35

What is performance profiling, and what should teams measure in a mobile app?

Accepted Answer

Performance profiling records how an app uses processor time, memory, rendering frames, network requests, and battery during realistic use. Teams should measure startup time, scrolling smoothness, and responsiveness to taps on representative devices. Findings guide fixes, so profiling should happen regularly rather than only before release.

Question 36

Why can a cross-platform app feel slower on lower-end devices?

Accepted Answer

Extra layers such as bridges, web views, or interpreted runtimes can add overhead that becomes noticeable when processors and memory are limited. Heavy animations, large lists, and unoptimized images also cost more on modest hardware. Teams should test on a range of devices, including older models, and optimize the parts users touch most.

Question 37

What is code signing, and why do app stores require it?

Accepted Answer

Code signing attaches a cryptographic signature to an app package using a developer's certificate, so the platform can verify who published it and that it has not been altered. App stores and operating systems require valid signatures before installing or distributing software. Protecting signing keys matters greatly.

Question 38

What is a release channel, and how do teams use staged rollouts?

Accepted Answer

A release channel is a distribution track, such as internal testing, beta testing, or production, that determines which users receive a build. Staged rollouts send a new version to a small percentage of users first, then widen availability if crash rates and feedback look healthy. It limits the impact of problems discovered after release.

Question 39

What information should a store listing and release notes include?

Accepted Answer

A store listing should describe the app's purpose, show accurate screenshots for the target devices, and state clearly what data the app collects. Release notes should summarize user-facing changes, fixes, and any required actions in plain language. Accurate listings build trust and help reviewers approve submissions without delays.

Question 40

How can a team keep an app secure when using shared libraries?

Accepted Answer

Teams should review third-party libraries before adoption, keep dependencies updated, and remove packages that are no longer maintained. Sensitive data such as tokens belongs in platform secure storage rather than plain files or unencrypted preferences. Automated scanning and least-privilege permissions reduce exposure further.

Cross-Platform Mobile Development Flashcards

1Core Concepts of Cross-Platform Development

2Native, Hybrid, and Web Approaches

3Frameworks and Development Tooling

4User Interface and Platform Conventions

5Testing, Performance, and Distribution

Learning Resources