Easy interview questions in Mobile Dev, page 3
What is the difference between project-level and module-level build.gradle?
Project level sets plugin repos and shared versions; module level sets dependencies, build types, and flavors.
Difference between project and module build.gradle files?
This tests your understanding of Gradle's project structure and build configuration scope. The project-level file configures global settings like repositories, while the module-level file configures specifics like dependencies and app ID.
Project-level vs. module-level build.gradle files
This tests your grasp of Gradle's project/module structure. A good answer defines the project-level file for global settings (repositories, plugins) and the module-level for specifics (SDK versions, dependencies). A red flag is confusing their roles.
What is @State in SwiftUI and how does it affect the view?
Tests declarative data flow ownership. A strong answer defines @State as private value-type storage owned by the view that triggers a body re-evaluation on mutation. Red flag: confusing it with external data sources like @ObservedObject or @Binding.
Explain StatelessWidget vs StatefulWidget and when to choose each
This tests immutable UI versus persistent state. StatelessWidget rebuilds when config changes; StatefulWidget owns State surviving rebuilds. Use StatelessWidget for static UI and StatefulWidget for interactive elements.
What is the res directory and how do you use orientation qualifiers?
Res/ holds non-code assets; create layout-port/ and layout-land/ with identical XML filenames for automatic framework selection.
What is the `res/` directory and how do you use resource qualifiers?
This tests your grasp of Android's resource system. Explain that res/ separates assets from code and that qualifiers (e.g., layout-land) let the OS pick the right layout. A red flag is checking orientation manually in code instead of using this system.
Explain the res/ directory and resource qualifiers for layouts
Tests your grasp of Android's core resource system. A good answer defines res/ for non-code assets, explains how qualifiers like layout-land match device state, and provides a concrete example.
UIViewController lifecycle states: network vs geometry updates
Tests UIViewController lifecycle states and separation of data vs layout. Strong answers list loadView to viewDidDisappear, start network in viewDidLoad or viewWillAppear, and geometry in viewDidLayoutSubviews. Red flag: network calls inside layout methods.
What is the build method's purpose and key constraints?
It returns a Widget tree, can run every frame, must avoid side effects, and uses BuildContext for inherited data.
ScrollView versus FlatList for long lists
ScrollView mounts all children at once; FlatList virtualizes, rendering only on-screen items plus a buffer. Use ScrollView for small/fixed content, FlatList for long/dynamic data.
FlatList data, renderItem, and keyExtractor
Data is the array, renderItem maps each item to a component, keyExtractor returns a stable unique key letting React reconcile and reuse rows.
Describe the iOS app lifecycle and SceneDelegate methods
Not running, inactive, active, background, suspended; SceneDelegate handles sceneDidBecomeActive, sceneWillResignActive, sceneDidEnterBackground, sceneWillEnterForeground.
Describe the Android Activity lifecycle and callback order
Away calls onPause then onStop; back calls onRestart, onStart, onResume; onCreate only runs after destruction.
Trace an Activity's lifecycle when a user navigates away and returns
This tests your understanding of resource management and state preservation, not just memorization. A great answer traces onPause -> onStop when leaving, and onRestart -> onStart -> onResume when returning, explaining what happens in each.
Describe the Android Activity lifecycle when navigating away and back
Tests understanding of resource management via lifecycle callbacks. A good answer traces onPause -> onStop -> onRestart -> onStart -> onResume, explaining what work happens in each.
Explain UIKit MVC and the Massive View Controller problem
Model holds data, View displays it, Controller mediates between them; the view controller accretes networking, parsing, and logic into a Massive View Controller.
In a Row, how do you space children evenly across the width?
Set mainAxisAlignment to spaceEvenly; contrast with spaceBetween and spaceAround.
Activity rotation: what happens to EditText text?
Rotation destroys and recreates the Activity; EditText auto-saves text if it has an ID, else onSaveInstanceState or SavedStateHandle.
What happens to an Activity and its text on screen rotation?
Tests understanding of configuration changes and state preservation. A great answer explains the Activity is destroyed and recreated, EditText state is often saved automatically, but the robust solution is using a ViewModel with SavedStateHandle.
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