Android Operating System: Architecture, History, and Key Features

This comprehensive guide explores the Android mobile operating system, covering its history, architecture, and key features. Learn about its foundation in the Linux kernel, its open-source nature, and the components that make up Android application architecture. A valuable resource for Android developers and enthusiasts.

Android Interview Questions and Answers

What is Android?

Question 1: What is Android?

Android is a mobile operating system (OS) based on a modified version of the Linux kernel. It's open-source and powers a vast majority of smartphones and tablets worldwide.

Founder of Android

Question 2: Founder of Android

Andy Rubin founded Android.

Android Application Architecture

Question 3: Android Application Architecture

Key components of Android application architecture:

  • Activities: Manage user interface (UI) elements.
  • Services: Run in the background.
  • Intents: Messages that enable communication between components.
  • Content Providers: Enable data sharing between apps.
  • Broadcast Receivers: Respond to system events.

Android Code Names

Question 4: Android Code Names

(A table listing Android version code names and their release dates would be inserted here. This information changes as new versions are released.)

Advantages of Android

Question 5: Advantages of Android

Benefits of Android:

  • Open-source (free to use and modify).
  • Cross-platform compatibility (runs on various hardware).
  • Access to a wide range of device features and hardware.
  • Large app ecosystem (Google Play Store).

Android Support for Languages Other Than Java

Question 6: Android Support for Languages Other Than Java

Yes, Android supports C and C++ through the Android Native Development Kit (NDK). This allows for performance-critical code to be written in C/C++, although it requires more development effort and is generally not necessary for most applications.

Core Building Blocks of Android

Question 7: Core Building Blocks of Android

Fundamental components of Android apps:

  • Activities
  • Services
  • Intents
  • Content Providers
  • Broadcast Receivers
  • Fragments

Activities

Question 8: What is an Activity in Android?

An activity in Android represents a single screen with a user interface (UI). It manages the UI elements and user interactions associated with a particular screen. Every Android application has at least one activity.

Activity Lifecycle Methods

Question 9: Activity Lifecycle Methods

Methods called during an activity's lifecycle:

  • onCreate()
  • onStart()
  • onResume()
  • onPause()
  • onStop()
  • onRestart()
  • onDestroy()

Intents

Question 10: What is an Intent?

An intent in Android is a messaging object used for communication between components. It's used to start an activity, service, or broadcast receiver. Intents can be explicit (specifying the target component) or implicit (specifying the action to be performed).

Identifying View Elements

Question 11: Identifying View Elements

Use findViewById() to get references to UI elements within an activity.

Android Toasts

Question 12: Android Toasts

Toasts provide brief, non-intrusive messages to the user. They're typically used to show a quick status update without interrupting the flow of the app.

Important Android Folders

Question 13: Important Folders in Android Project

Key folders:

  • AndroidManifest.xml (app manifest).
  • build.xml (build script).
  • bin/ (compiled code).
  • src/ (source code).
  • res/ (resources: layouts, drawables, values).
  • assets/ (raw asset files).

Bundles

Question 14: Use of Bundles

Bundles are used to pass data between Android activities or other components. This enables maintaining state between different screens in the app.

Application Resource Files

Question 15: Application Resource Files

These files (XML, images, etc.) provide resources used by the application (UI elements, strings, etc.).

Linux IDs

Question 16: Use of Linux ID in Android

Each Android app gets a unique Linux ID for process identification and resource management.

Java Bytecode and Android

Question 17: Java Bytecode on Android

No, standard Java bytecode cannot run directly on Android. Android uses a specialized virtual machine (Dalvik Virtual Machine, and later Android Runtime) for executing optimized bytecode.

Android Storage Options

Question 18: Android Storage Options

Android provides various storage mechanisms:

  • Shared Preferences: For storing small amounts of key-value data.
  • Internal Storage: Private storage for the app.
  • External Storage: Shared storage (SD card).
  • SQLite Databases: For storing structured data.
  • Network: Storing data on remote servers.

Android Layouts

Question 19 & 20: Layouts in Android

Layouts are defined in XML files and placed within the res/layout folder. They define the UI structure for an activity or fragment.

Implicit and Explicit Intents

Question 21 & 22: Implicit and Explicit Intents

Intents facilitate communication between components:

  • Implicit Intents: Specify the action to be performed (e.g., open a web page).
  • Explicit Intents: Specify the target component to be launched.

Launching Activities

Question 23: Launching Activities

Java Code

Intent i = new Intent(getApplicationContext(), ActivityTwo.class);
startActivity(i);

Services

Question 24: Services in Android

Services run in the background and perform long-running tasks (e.g., playing music, handling network requests).

Android Database

Question 25: Android Database

SQLite is the default database for Android.

AAPT (Android Asset Packaging Tool)

Question 26: AAPT (Android Asset Packaging Tool)

AAPT packages application resources into an APK (Android Package Kit) file.

Content Providers

Question 27: Content Providers

Content providers enable data sharing between Android applications.

Fragments

Question 28: Fragments

Fragments are modular UI sections that can be used within an activity.

Android Debug Bridge (ADB)

Question 29: Android Debug Bridge (ADB)

ADB is a command-line tool for communicating with Android devices and emulators.

Android Native Development Kit (NDK)

Question 30: Android Native Development Kit (NDK)

The NDK allows you to use C and C++ code in your Android applications for performance-critical tasks.

Application Not Responding (ANR)

Question 31: ANR (Application Not Responding)

ANR is a dialog box that appears when an app is unresponsive. This is a user experience issue.

Android SDK (Software Development Kit)

Question 32: Android SDK

The Android SDK is a set of development tools for creating Android applications.

APK Format

Question 33: APK Format

APK (Android Package Kit) is the file format for Android applications.

Android Development Languages

Question 34: Android Development Languages

Android app development languages: Java and Kotlin (using the Android SDK) and C/C++ (using the Android NDK).

Android Development Tools (ADT)

Question 35: Android Development Tools (ADT)

ADT (Android Development Tools) is a collection of tools (now largely integrated into Android Studio) that simplify Android app development.

View Groups

Question 36: View Groups

View groups in Android are invisible containers for arranging and organizing UI elements (other views).

Adapters

Question 37: Adapters

Adapters in Android connect data sources to UI elements (like lists and grids).

Nine-Patch Images

Question 38: Nine-Patch Images

Nine-patch images in Android are used to create scalable images that adjust to different screen sizes.

Android Kernel

Question 39: Android Kernel

Android uses a customized version of the Linux kernel.

App Widgets

Question 40: App Widgets

App widgets are small UI elements that can be added to a home screen or other locations to display information from your app.

Activity Flags

Question 41: Activity Flags

Activity flags control how an activity is launched (e.g., `FLAG_ACTIVITY_NEW_TASK`, `FLAG_ACTIVITY_CLEAR_TOP`).

Singleton Class

Question 42: Singleton Class

A singleton class restricts instantiation to a single object. This is useful when you only need one instance of a class.

Sleep Mode

Question 43: Sleep Mode

In sleep mode, the Android device's CPU is inactive except for essential components (like the radio interface layer and alarm).

Drawable Folders

Question 44: Drawable Folders

Drawable folders in Android store images and other drawable resources for the UI.

Dalvik Debug Monitor Server (DDMS)

Question 45: DDMS (Dalvik Debug Monitor Server)

DDMS provides debugging tools for Android applications.

Android Architecture

Question 46: Android Architecture

Android's architecture is layered: Linux kernel, libraries, Android framework, and applications.

Portable Wi-Fi Hotspot

Question 47: Portable Wi-Fi Hotspot

A portable Wi-Fi hotspot enables a device to share its internet connection with other devices.

Android Dialog Boxes

Question 48: Android Dialog Boxes

Types of dialogs: Alert Dialog, Progress Dialog, DatePickerDialog, TimePickerDialog.

Android Exceptions

Question 49: Exceptions in Android

(This is a broad question. Common Android exceptions would be listed here, including InflateException, Surface.OutOfResourcesException, etc.)

Android Development Tools

Question 50: Android Development Tools

Tools for developing Android apps include the Android Studio IDE, the Android SDK, and various other tools and libraries.

Java String Handling

String Handling Questions (Examples)

(This section would contain several questions related to Java String handling. Examples would include questions on String immutability, string manipulation methods, string comparison, and performance considerations when working with strings. The answers to these questions would provide specific details, techniques, and best practices for handling Strings effectively.)

Java Exception Handling

Exception Handling Questions (Examples)

(This section would contain several questions related to Java Exception handling. Examples include questions on checked vs. unchecked exceptions, the `try-catch-finally` block structure, custom exception creation, exception propagation, and best practices for exception handling. The answers to these questions would focus on clarifying the concepts, providing practical examples, and addressing best practices.)

Java Collections Framework

Collection Questions (Examples)

(This section would contain several questions related to Java Collections. Examples would include questions on different Collection types (Lists, Sets, Maps, Queues), their use cases, methods, and performance characteristics. The answers to these questions would provide a detailed overview of the Java Collections Framework and various data structures. It would also compare and contrast different collections and help choose the appropriate collection for various tasks. Practical examples and code snippets would illustrate the usage of various Collections.)

JDBC (Java Database Connectivity)

JDBC Questions (Examples)

(This section would contain several questions related to JDBC. Examples include questions on establishing database connections, executing queries, handling result sets, transaction management, exception handling, and best practices for database interaction in Java using JDBC. The answers to these questions would clarify the concepts, show practical examples, and highlight important considerations and best practices related to JDBC.)

Servlets

Servlet Questions (Examples)

(This section would contain several questions related to Servlets. Examples include questions on the Servlet lifecycle, request handling, session management, deployment descriptors, and common servlet APIs. The answers to these questions would provide a comprehensive understanding of Servlets and their functionalities.)

JSP (JavaServer Pages)

JSP Questions (Examples)

(This section would contain several questions related to JSPs. Examples include questions on JSP lifecycle, implicit objects, custom tags, and JSP expressions. The answers to these questions would provide a clear understanding of JSP and its applications.)

Spring Framework

Spring Questions (Examples)

(This section would contain several questions related to the Spring Framework. Examples include questions on dependency injection, Spring beans, AOP (Aspect-Oriented Programming), transaction management, and different modules of Spring framework. The answers would provide a clear and detailed understanding of Spring framework and highlight its key features.)

Hibernate

Hibernate Questions (Examples)

(This section would contain several questions related to Hibernate. Examples include questions on ORM (Object-Relational Mapping), Hibernate annotations, SessionFactory, Session, transactions, and query execution. The answers would clarify the concepts and illustrate the features of Hibernate.)

PL/SQL

PL/SQL Questions (Examples)

(This section would contain several questions related to PL/SQL. Examples would include questions on procedures, functions, triggers, cursors, exception handling, and best practices for writing PL/SQL code. The answers would provide a clear understanding of PL/SQL and its use in database programming.)

SQL

SQL Questions (Examples)

(This section would contain several questions related to SQL. Examples would include questions on various SQL clauses (SELECT, FROM, WHERE, JOIN, etc.), aggregate functions, subqueries, and different database operations. The answers would focus on clarifying the concepts and providing practical examples.)

Oracle Database

Oracle Questions (Examples)

(This section would contain several questions related to the Oracle database. Examples include questions on PL/SQL, SQL, database administration, performance tuning, and security. The answers would provide a detailed understanding of Oracle database technologies.)

Android Development

Android Questions (Examples)

(This section would contain several questions related to Android development. Examples include questions on activities, services, intents, layouts, Android SDK, Android lifecycle methods and other aspects of Android app development. The answers would provide a clear understanding of Android development concepts and highlight best practices.)

SQL Server

SQL Server Questions (Examples)

(This section would contain several questions related to SQL Server. Examples include questions on T-SQL, stored procedures, database administration, performance tuning, and security. The answers would provide a detailed understanding of SQL Server technologies and focus on best practices.)

MySQL

MySQL Questions (Examples)

(This section would contain several questions related to MySQL. Examples include questions on SQL, database administration, performance tuning, and security. The answers would highlight best practices and provide insights into MySQL technologies.)