Essential Android Development Concepts & FAQs

Posted on Jun 24, 2025 in Computers

Essential Android Development Concepts

1. What is Android?

Android is an open-source mobile operating system based on Linux and developed by Google. It is used primarily for touchscreen devices like smartphones, tablets, and wearables. Android provides an environment for developing applications using Java and Kotlin, and it supports various features like sensors, touch input, and multimedia.

2. What are the components of an Android application?

An Android application consists of the following core components:

• Activities: A single screen or user interface in the application.
• Services: Background tasks that run independently of the user interface.
• Content Providers: Used to manage application data and share it with other applications.
• Broadcast Receivers: Listen for system or application events.
• Fragments: Reusable UI components within activities.

3. What is the AndroidManifest.xml file?

The AndroidManifest.xml file is an essential part of every Android application. It contains important information about the app, such as its package name, components (activities, services, etc.), required permissions, and hardware or software features that the app needs. It also declares activities and their relationship with intents.

4. What is an Intent in Android?

An Intent is an abstract description of an operation to be performed. It can be used to:

• Start an activity or service.
• Deliver a broadcast message.
• Start an activity for a result (passing data between activities).

Intent types:

• Explicit Intent: Specifies the exact component to start (e.g., starting a specific activity by its class name).
• Implicit Intent: Describes the action to be performed, allowing the Android system to determine the appropriate application component to handle it.

5. What is the difference between an Activity and a Fragment?

• Activity: Represents a single screen in an application. It manages user interactions and serves as the primary entry point for any interaction with the app.
• Fragment: A modular section of an activity. It is reusable and can be combined with other fragments to create flexible UI designs. Fragments exist within an activity but can also be reused across different activities.

6. What is the Android Activity Lifecycle?

The Activity lifecycle refers to the sequence of states through which an activity passes from its creation to its destruction. These states include:

• onCreate(): Called when the activity is first created.
• onStart(): Called when the activity becomes visible to the user.
• onResume(): Called when the activity starts interacting with the user.
• onPause(): Called when the activity is no longer in the foreground but still partially visible.
• onStop(): Called when the activity is no longer visible to the user.
• onDestroy(): Called before the activity is destroyed.

7. What is an AsyncTask in Android?

AsyncTask is a class used to perform background operations (such as network operations) and update the UI without blocking the main thread. It provides methods to execute tasks in the background (doInBackground()) and publish results on the UI thread (onPostExecute()).

8. What is a Service in Android?

A Service is an application component that runs in the background to perform long-running operations. It does not have a user interface and is used for tasks like playing music, downloading files, or handling network requests. There are two main types:

• Started Service: Runs indefinitely until explicitly stopped by the application.
• Bound Service: Allows interaction between components and can be bound by an activity or another service.

9. What are Content Providers in Android?

Content Providers are used to manage and share data between different applications. For example, contacts or media (photos, videos) data are stored in content providers, and applications can interact with them through a standard API. Content providers use a URI (Uniform Resource Identifier) to identify data.

10. What is the role of SQLite in Android?

SQLite is a lightweight database engine used for local data storage in Android applications. It allows apps to store structured data, making it possible to query, insert, update, and delete data efficiently. Each application typically has its own private SQLite database.

11. What is a Broadcast Receiver in Android?

A Broadcast Receiver is an Android component that listens for system-wide or app-specific broadcast messages, such as notifications for system events (e.g., battery status, Wi-Fi connectivity changes). It allows applications to respond to these events without needing to run continuously.

12. What is Gradle in Android development?

Gradle is a build automation tool used to compile and package Android applications. It is the default build system for Android Studio, allowing developers to define dependencies, configure project settings, and manage build variants (like debug or release versions).

13. What is a View in Android?

A View is the basic building block for UI components in Android. It represents any visual element, such as buttons, text fields, or images. Views are arranged within ViewGroups (containers like LinearLayout or RelativeLayout).

14. What is the difference between LinearLayout and RelativeLayout?

• LinearLayout: Arranges its child views in a single direction (either vertically or horizontally). Each child view takes up space according to its layout parameters.
• RelativeLayout: Allows child views to be positioned relative to each other or to the parent container. It offers more flexibility for complex UIs compared to LinearLayout.

15. What is an Adapter in Android?

An Adapter is a bridge between a data source (such as an array or list) and a View (like ListView or RecyclerView). It manages the data for the views and generates views for individual items in the data source.

16. What is RecyclerView in Android?

RecyclerView is a more advanced and flexible version of ListView. It is used to display large datasets efficiently by recycling view holders and using a layout manager to define how items should appear on the screen. RecyclerView also supports animations, item decorations, and more.

17. What is the difference between ListView and RecyclerView?

• ListView: An older widget for displaying lists, less efficient for large datasets due to its lack of view recycling.
• RecyclerView: A more efficient widget for displaying lists with better performance, supports flexible layouts (e.g., grid or staggered), and is more customizable.

18. What are Permissions in Android?

Permissions are security mechanisms that allow applications to request access to restricted system resources like the internet, camera, or contacts. Starting from Android 6.0 (API level 23), permissions need to be requested at runtime.

19. What is the difference between onCreate() and onStart() in Activity lifecycle?

• onCreate(): Called when the activity is first created, typically used for initializing the activity.
• onStart(): Called when the activity is becoming visible to the user, after onCreate().

20. What is the use of onSaveInstanceState() and onRestoreInstanceState()?

• onSaveInstanceState(): Called to save the activity’s state before it is destroyed (e.g., when the device configuration changes, like rotation).
• onRestoreInstanceState(): Called after the activity is recreated, allowing it to restore previously saved state information.

21. What is a Handler in Android?

A Handler allows you to send and process Message and Runnable objects associated with a thread’s MessageQueue. It is often used for updating the UI from background threads.

22. What is Retrofit in Android?

Retrofit is a type-safe HTTP client for Android that simplifies network requests. It allows developers to define REST API interfaces and map them to HTTP requests using annotations. It supports multiple serialization formats like JSON and XML.

23. What is a Singleton Pattern in Android?

The Singleton pattern ensures that a class has only one instance and provides a global point of access to it. It is often used in Android to manage resources like network clients, database connections, or shared preferences managers.

24. What is the difference between SharedPreferences and SQLite?

• SharedPreferences: Used for storing simple key-value pairs, such as user preferences or application settings.
• SQLite: A full-fledged relational database used for more complex, structured data storage and querying.

25. What is ANR (Application Not Responding) in Android?

An ANR (Application Not Responding) occurs when the main thread of an Android application is blocked for too long (typically more than 5 seconds), usually due to long-running operations. This results in the system displaying an “Application Not Responding” dialog to the user.

These questions and answers cover a broad spectrum of Android development topics, from app architecture to specific Android components and best practices.