Android interview questions with answers

Android interview questions along with sample answers:

1. What is Android?

Answer:
Android is an open-source operating system developed by Google, designed primarily for touchscreen mobile devices like smartphones and tablets. It’s built on a modified version of the Linux kernel and provides a rich application framework that allows developers to create innovative apps and games for mobile devices.

2. What are the main components of an Android application?

Answer:
The main components of an Android application are:

• Activities: Represent a single screen with a user interface. An app can have multiple activities.
• Services: Run in the background to perform long-running operations or to perform work for remote processes.
• Broadcast Receivers: Respond to system-wide broadcast announcements, such as when the device is charging or when the Wi-Fi is turned on.
• Content Providers: Manage a shared set of app data that can be accessed by other apps.

3. What is an Activity in Android?

Answer:
An Activity is a component of an Android application that provides a user interface. It acts as a single screen in the app where users can interact with the app. Each Activity is implemented as a subclass of Activity and typically represents one screen or a portion of the screen in the app.

4. Explain the Android Activity Lifecycle.

Answer:
The Android Activity Lifecycle includes several key states:

• onCreate(): Called when the activity is first created. This is where you initialize your activity.
• onStart(): Called when the activity becomes visible to the user.
• onResume(): Called when the activity starts interacting with the user.
• onPause(): Called when the system is about to start resuming another activity.
• onStop(): Called when the activity is no longer visible to the user.
• onDestroy(): Called before the activity is destroyed.

Understanding these lifecycle methods is crucial for managing resources and handling transitions between different states.

5. What is an Intent in Android?

Answer:
An Intent is a messaging object used to request an action from another app component. It can be used to start activities, send broadcasts, or start services. Intents can be explicit (specifying the exact component) or implicit (requesting an action to be performed by any component that can handle it).

6. How does Android handle background tasks?

Answer:
Android provides several ways to handle background tasks:

• Services: For long-running background operations.
• AsyncTask: For performing background operations and publishing results on the UI thread.
• JobScheduler: For scheduling tasks to run in the background at specified times or conditions.
• WorkManager: Provides a modern, flexible API for managing background work, supporting both immediate and deferred execution with guaranteed execution.

7. What is the difference between Serializable and Parcelable in Android?

Answer:
Both Serializable and Parcelable are used to serialize objects so they can be passed between activities or saved to storage:

• Serializable: A standard Java interface for serialization. It’s simpler to use but less efficient compared to Parcelable.
• Parcelable: An Android-specific interface that allows you to serialize objects more efficiently. It requires more code to implement but performs better, which is important for Android applications.

8. What are Fragments in Android?

Answer:
Fragments are reusable components of an activity that represent a portion of the user interface. They allow for modular and flexible design of UI, especially on devices with varying screen sizes. A fragment is a piece of an activity, which has its own lifecycle and can be combined with other fragments within a single activity.

9. Explain the concept of ContentProvider in Android.

Answer:
A ContentProvider manages access to a central repository of data. It provides a way for apps to interact with data from other apps securely. It uses URIs to identify data and allows other applications to perform operations like query, insert, update, and delete on that data.

10. What is a ViewModel in Android?

Answer:
A ViewModel is a part of Android’s Architecture Components. It is designed to store and manage UI-related data in a lifecycle-conscious way. It allows data to survive configuration changes like screen rotations, which helps in maintaining the UI state and reduces the need to reload data when the activity or fragment is recreated.

11. What are LiveData and how do they work?

Answer:
LiveData is an observable data holder class that is lifecycle-aware. It means that it respects the lifecycle of other app components, such as activities and fragments. LiveData objects can be observed for changes, and they only send updates to active observers. This helps prevent memory leaks and ensures that the UI is always updated with the latest data.

12. What is a RecyclerView and how does it differ from ListView?

Answer:
RecyclerView is a more flexible and efficient version of ListView. It provides better performance and more features, such as:

• ViewHolder pattern: Reduces the number of calls to findViewById(), improving performance.
• LayoutManagers: Allows for various layouts (e.g., grid, linear, staggered).
• ItemDecoration and ItemAnimator: Allows for adding decorations and animations to items.

ListView is simpler but less flexible and less efficient with large data sets compared to RecyclerView.

13. How do you handle configuration changes in Android, such as device rotation?

Answer:
Configuration changes like device rotation can be handled in several ways:

• Retain Instance State: Save and restore data using onSaveInstanceState() and onRestoreInstanceState()methods.
• ViewModel: Use ViewModel to store UI-related data that survives configuration changes.
• Fragments: Use fragment arguments or retain fragments to maintain state.

14. What is Dependency Injection and how is it used in Android?

Answer:
Dependency Injection (DI) is a design pattern used to manage object dependencies. In Android, it helps to decouple components and manage dependencies efficiently. Common DI frameworks for Android include:

• Dagger: A compile-time DI framework that generates code to handle dependency injection.
• Hilt: A higher-level DI library built on top of Dagger that simplifies DI setup.

15. What are Android Jetpack components?

Answer:
Android Jetpack is a set of libraries, tools, and architectural guidance to help developers build high-quality apps more easily. It includes:

• Architecture Components: Such as Room, ViewModel, LiveData, and Navigation.
• UI Components: Such as RecyclerView, CardView, and ConstraintLayout.
• Behavior Components: Such as WorkManager and Paging.
• Foundation Components: Such as AppCompat, Android KTX, and Test.