Android: Mobile Application Development

Mobile application development refers to the process of creating software designed specifically for use on mobile devices like smartphones, tablets, and other portable gadgets. While mobile phones are the most common devices for mobile applications, the category also extends to Personal Digital Assistants (PDAs), Enterprise Digital Assistants (EDAs), and even digital cameras. These applications can be pre-installed on devices during manufacturing, offered through app stores (such as the Google Play Store for Android), or delivered via web-based client-server models that users can access through a browser.

Due to the competitive nature of the mobile market, applications can vary widely in size, complexity, and functionality, ranging from simple utilities to feature-rich applications with multiple screens, hardware configurations, and specifications.

Introduction to Android: A Leading Mobile Operating System

In this chapter, we focus on Android, one of the most popular and widely used mobile operating systems. Android has a significant presence in the mobile application development world due to its vast user base and the flexibility it offers to developers. Developed by Google, Android provides a platform for building apps that can run on a wide range of devices with varying hardware configurations.

Key Topics Covered in This Chapter:

1. Android Applications: We will delve into the components that make up an Android application, including activities, services, content providers, and broadcast receivers. Understanding these components is essential for creating robust and efficient Android applications.
2. The Android Manifest File: This crucial file provides essential information about the application to the Android operating system. You will learn how to configure and utilize this file in your development projects.
3. Downloading and Installing Android: A step-by-step guide will be provided on how to download and install the necessary tools to start developing Android applications, including the Android SDK, JDK, and Eclipse IDE.
4. Development Environment: Setting up your development environment is a critical first step in Android app development. You’ll learn about the tools and frameworks that make the development process more streamlined and efficient.
5. Developing and Running Your First Android Application: Towards the end of this chapter, we’ll guide you through creating your very first Android app, showing you how to develop, test, and execute it.

By the end of this chapter, you’ll have a foundational understanding of Android and be equipped to start developing your own mobile applications for this powerful platform.

Install Android Development Tools

Before you can start developing Android applications, you need to set up your development environment. This involves downloading, configuring, and installing several software components that make up the Android Integrated Development Environment (IDE). Below are the key prerequisites required to get started:

1. Java Development Kit (JDK)

Since Android applications are primarily written in Java, the Java Development Kit (JDK) is essential. The JDK includes everything you need to compile and run Java applications, including the Java Runtime Environment (JRE) and development tools like the Java compiler.

To install the JDK:

• Visit the official Oracle website or use OpenJDK, and download the appropriate version for your operating system.
• Follow the installation instructions based on your system (Windows, macOS, or Linux).

2. Android Software Development Kit (SDK)

The Android Software Development Kit (SDK) is a collection of tools, libraries, and APIs required for developing Android applications. The SDK includes various tools like the Android Debug Bridge (ADB), emulator, and platform-specific libraries.

To install the Android SDK:

• Go to the official Android developer site and download the Android SDK.
• You will need to install the SDK Manager, which allows you to download specific Android platform packages and tools.
• Once the SDK Manager is installed, you can choose which Android versions and tools you want to install for your development environment.

3. Eclipse IDE

Eclipse IDE is an open-source Integrated Development Environment used for developing Android applications. It provides support for Java and XML, along with features such as code completion, debugging tools, and built-in version control systems.

To install Eclipse:

• Download the latest version of Eclipse IDE for Java Developers from the official Eclipse website.
• Follow the installation steps for your specific operating system.

Once you have these three components — JDK, Android SDK, and Eclipse IDE — installed and configured, your development environment will be ready. You can now begin building, testing, and deploying Android applications.

Android Applications Development

Android applications are primarily developed using Java and Kotlin. The Java Android development focuses on the essential classes and libraries needed for mobile devices.

Developers need to have a basic understanding of Java to begin developing Android apps.

If you’re new to Java programming, don’t worry — there are plenty of resources, such as books and online tutorials, to help you grasp the fundamentals of the language. Once you have a basic understanding of Java, you’re well on your way to creating Android applications.

In addition to Java, other technologies such as XML and Apache Ant scripting are integral parts of Android development. While Java provides the core functionality, XML is used for defining user interfaces and other application components, and Apache Maven is a tool used for automating tasks like building the application.

What You Need to Know Before Developing Android Apps

1. Java Basics:
   • Since Android applications are primarily written in Java, a solid understanding of the basic syntax, object-oriented principles, and libraries is essential. Key concepts like classes, objects, inheritance, and interfaces are fundamental to Android development.
2. XML:
   • While Java handles the logic and functionality of your application, XML is used for designing user interfaces (UIs). For example, you’ll use XML to define layouts, buttons, text fields, and other UI elements that users will interact with.
3. Apache Maven:
   • Apache Maven is a build automation tool that helps streamline tasks such as compiling the source code, packaging the app, and managing dependencies. Understanding how to work with this tool will make your development process smoother.

Once you have a grasp of Java and XML, you’ll be ready to dive into Android app development. The next step is to familiarize yourself with the key components of an Android application, which we’ll explore in the following sections.

Understanding Android APIs

In the world of Android development, APIs (Application Programming Interfaces) play a critical role in allowing developers to create powerful applications. An API is essentially a set of protocols and tools that enable different software systems to communicate with one another. It provides the specifications necessary to develop programs, and these building blocks are connected by the programmer to create functional applications.

For Android, the applications you interact with are all built on top of these APIs, which provide the necessary interface between the app and the underlying Android system. Over time, Android has introduced several new APIs to offer enhanced features for users and developers alike.

What is an Android API Level?

Each version of the Android platform introduces new APIs, and these are classified under different API levels. The API level refers to the version of the Android API that a particular Android platform version supports. This number determines which set of functionalities, classes, and libraries are available to developers and which older versions of Android are compatible with the current API.

In simple terms, the API level is an index that provides a set of features for each Android version, allowing developers to know which functionalities they can use when building apps for a specific Android version. For example, Android 4.4 KitKat (API level 19) provides a certain set of APIs, while Android 5.0 Lollipop (API level 21) provides an extended or different set.

Features of Android APIs

1. Compatibility and Backward Compatibility
   • Android API levels are designed with backward compatibility in mind. This ensures that new features added in higher API levels don’t break functionality on older devices. For example, API level 14 (Android 4.0 Ice Cream Sandwich) can still support applications designed for API level 3 (Android 1.5 Cupcake).
   • Older APIs are not usually removed entirely but marked as deprecated. This means that while they are still available for use, developers are encouraged to move towards newer alternatives for better performance and security.
2. Additions and Changes
   • When a new API level is introduced, it often comes with new features or replacements for outdated functionality. While new parts are added, older elements might be phased out or deprecated, ensuring the platform continues to improve without completely discarding previous work.
3. Security and Robustness
   • Occasionally, certain features from old APIs are removed to strengthen the security of the system or to improve overall performance. This helps the system remain secure and prevents legacy code from posing risks.
4. Single API Support Per Android Version
   • Each Android version only supports one API level. For example, Android KitKat (version 4.4) only supports API level 19. This ensures that each version of Android is tightly coupled with a specific set of features and capabilities.

Conclusion

Android APIs are essential for building Android applications. They provide a framework for developers to communicate with the Android operating system, enabling access to features like user interface elements, sensors, multimedia, and much more. By understanding API levels and how they evolve with each Android version, developers can ensure that their applications are both functional and compatible with various Android devices, offering users a seamless experience.

As Android continues to evolve, it remains committed to supporting backward compatibility, allowing developers to create apps that work on a wide range of devices, from the latest models to older ones.

Android Introduction

The mobile phone industry has experienced a massive transformation in recent decades, with a surge in demand for mobile devices. Today’s smartphones are far more than just communication tools — they are powerful, versatile devices that serve a wide range of purposes. From browsing the internet to gaming, photography, and even running business applications, smartphones have become indispensable in daily life. At the core of these devices is their operating system (OS), which powers all the functionalities of a mobile phone.

While many mobile OS options exist, Android stands out as one of the most popular and widely used platforms in the world. Developed by Google Inc., Android was primarily designed for touchscreen mobile devices, offering an intuitive and user-friendly interface. Over the years, Android has evolved to power smartphones, tablets, wearables, and more, providing a versatile and customizable platform.

One of the key features of Android is that its applications are primarily developed in Java, which lies at the top of its development layers, making it a powerful choice for developers worldwide.

A Look at the Version History of Android

Android’s journey began in November 2007 when Android Beta was first released. This marked the beginning of Android’s evolution into one of the most successful mobile operating systems in the world. After its initial beta release, Android was commercially launched in September 2008 as Android 1.0. Since then, Android has undergone numerous updates and revisions, with new versions being released regularly to improve performance, add features, and enhance security.

The continuous development of Android has played a major role in shaping the mobile tech industry, offering flexibility, customization, and an ever-expanding range of applications.

The Android Architecture Stack

To develop applications for the Android platform, it’s essential for developers to have a deep understanding of its architecture. While users may see Android as a system that allows them to make calls, send text messages, share photos, and alter settings, developers need to look beyond these basic operations. A solid understanding of the Android architecture is required to effectively create applications.

The architecture of the Android system is structured as a software stack consisting of multiple layers, each serving a distinct purpose. These layers interact with each other, where each underlying layer provides services to the layer above it. The complete architecture is made up of the Operating System (OS), middleware, and essential applications. Each of these layers plays a crucial role in ensuring that Android runs smoothly and efficiently on various devices.

Layers of Android Architecture

1. Linux Kernel
   • At the very bottom of the Android architecture lies the Linux Kernel, responsible for managing the hardware drivers, memory management, process management, and security features. It serves as the foundation on which the Android OS is built.
2. Android Runtime (ART)
   • The Android Runtime (ART) layer is where things start to differ from traditional Java environments. Unlike the Java Virtual Machine (JVM), Android uses the Dalvik Virtual Machine (DVM), which is optimized for mobile devices with low memory and CPU constraints. This virtual machine enables the execution of Android applications, and it performs just-in-time (JIT) compilation and garbage collection for improved performance.

   For developers familiar with Java, it’s important to note that ART is part of the Android runtime that replaced Dalvik in later Android versions. ART offers ahead-of-time (AOT) compilation, resulting in improved application performance compared to Dalvik.

3. Libraries and Middleware
   • Above the Android runtime layer are the native libraries and middleware. These include libraries such as WebKit (for web browsing), OpenGL (for graphics rendering), and SQLite (for local database storage). Middleware services provide features for application components, including messaging, location services, and other important functionalities.
4. Application Framework
   • The Application Framework provides a higher-level interface to the Android system. It includes components such as the Activity Manager, Content Providers, Resource Manager, and Window Manager, which facilitate the development of Android apps. The application framework ensures that developers can easily access system-level features without dealing with low-level details.
5. Applications
   • The Applications Layer includes all the built-in applications that come with Android (such as the dialer, contacts, and email) as well as third-party applications. This layer interacts directly with the application framework, which simplifies development for third-party app developers by providing the necessary APIs and services.

Conclusion

The Android Architecture is a well-structured, layered framework that allows developers to build powerful applications while managing complexity. By understanding each layer — from the Linux kernel to the Android runtime and the application framework — developers can optimize their apps for performance, security, and user experience. This architecture ensures that Android remains versatile and efficient across different devices and use cases.

Linux Kernel in Android

At the heart of the Android operating system lies the Linux kernel, the lowest and most critical layer of the Android architecture. It acts as the bridge between the hardware and the rest of the Android software stack, providing a strong and stable foundation for the entire system.

Key Roles of the Linux Kernel in Android

1. Hardware Abstraction Layer
   • The Linux kernel serves as an abstraction layer between the hardware and software. It manages direct interactions with the hardware components of the device, such as the display, camera, and power management systems, through its built-in drivers.
2. Hardware Drivers Integration
   • The Linux kernel comes equipped with essential hardware drivers, including:
     • Display Driver: Manages screen output and rendering.
     • Camera Driver: Interfaces with the camera hardware, enabling photo and video capture.
     • Power Management Driver: Optimizes battery usage and manages power-related tasks.
   • For instance, when the Android OS is installed on a compatible device, the Linux kernel detects the hardware components, like the camera, and makes them accessible to the system through the appropriate drivers.
3. Core System Functionality
   • The core of the Android system relies on the Linux kernel, inheriting many features from the robust Linux OS. This includes process management, memory management, and file system management, all of which are essential for efficient multitasking and resource allocation.
4. Security and Stability
   • The Linux kernel enhances the security of Android by implementing features like process isolation and user permissions. It also manages system stability, reducing the chances of crashes or system failures by efficiently handling low-level operations.
5. Versatility and Compatibility
   • One of the strengths of using the Linux kernel is its ability to support a wide range of hardware configurations. This versatility allows Android to run smoothly on a variety of devices, from smartphones and tablets to smart TVs and wearables, with minimal compatibility issues.

Why the Linux Kernel is the Backbone of Android

The choice of the Linux kernel as the foundation of Android is due to its powerful and flexible nature. Linux is a proven operating system known for its performance and scalability. By building on top of Linux, Android inherits a reliable and efficient system that can adapt to different hardware and provide consistent performance across diverse devices.

Conclusion

The Linux kernel is the backbone of the Android operating system, providing the essential features and low-level management required for seamless operation. Its hardware drivers, security features, and versatile architecture form the basis of Android’s success, making it a robust and adaptable platform for millions of devices worldwide.

Android Native Libraries

The Android Libraries layer is positioned just above the Linux kernel in the Android architecture. These native libraries provide critical functions that enable the Android OS to handle various types of data and services efficiently. Written primarily in C and C++, these libraries offer high-performance processing and play a vital role in Android’s capabilities. Here’s a brief overview of some key Android native libraries:

1. WebKit

The WebKit library is the core browser engine used by Android to render and display web content. It interprets HTML, CSS, and JavaScript, allowing Android apps to embed web views and provide a rich browsing experience. WebKit ensures that web pages are displayed correctly and interactively within Android applications.

2. Media Framework

The Media Framework library handles multimedia processing on Android devices. It supports audio and video playback, recording, and streaming by using a variety of media codecs. This library allows apps to utilize features like audio playback, video playback, and image display, providing a seamless multimedia experience for users.

3. Surface Manager

The Surface Manager is responsible for managing surface manipulations on the device screen. It works in conjunction with the Window Manager to handle off-screen buffering, which helps create smooth transitions and animations. Off-screen buffering also supports transparency effects, making it possible to display overlapping UI elements with visual effects.

4. SQLite

SQLite is the lightweight database engine integrated into Android for data storage. It provides a relational database management system (RDBMS) without requiring a separate server process, making it ideal for mobile devices. Developers can use SQLite to store and manage app data efficiently, supporting features like querying, data insertion, and retrieval.

5. OpenGL

OpenGL is a powerful rendering engine used to create and display 2D and 3D graphics. Android utilizes OpenGL for hardware-accelerated graphics, allowing developers to render complex visuals, animations, and games. It provides a high-performance framework for building visually intensive applications, such as games and simulation apps.

Conclusion

The native libraries in Android provide essential functions that enhance the capabilities of the operating system. With libraries like WebKit, Media Framework, Surface Manager, SQLite, and OpenGL, Android can efficiently handle web content, multimedia, screen rendering, data storage, and graphics rendering. Understanding these libraries helps developers leverage the full potential of the Android platform and build high-performance applications.

Android Application Framework

The Android Application Framework is a set of core services and managers that provide the necessary tools and APIs for developers to build feature-rich and efficient mobile applications. This framework allows apps to interact seamlessly with the Android operating system. Here are the main components of the Android Application Framework:

1. Activity Manager

The Activity Manager handles the lifecycle of activities within an Android application. It manages the different states of an activity (e.g., created, started, resumed, paused, stopped) and ensures smooth transitions between activities. This component is crucial for handling user interactions and managing the app’s navigation.

2. Content Providers

Content Providers enable data sharing between applications. They manage access to structured data, allowing apps to query or modify data, such as contacts or media files. By using Content Providers, developers can create apps that share data securely across different applications while maintaining data privacy.

3. Telephony Manager

The Telephony Manager is responsible for managing voice calls. It provides access to telephony services and allows apps to handle tasks related to phone calls, such as checking the phone state, managing call status, and accessing subscriber information. This component is optional and is primarily used by apps that require voice call functionalities.

4. Location Manager

The Location Manager handles location-related tasks in an Android application. It allows apps to obtain the current location of the device using GPS, Wi-Fi, or cellular data. This component is essential for apps that rely on location-based services, such as maps, navigation, and location tracking.

5. Resource Manager

The Resource Manager is responsible for managing different types of resources used in an application, such as strings, layouts, images, and animations. It helps apps efficiently access and manage their resources, ensuring smooth performance and proper handling of different screen sizes and configurations.

Conclusion

The Android Application Framework provides a comprehensive set of services and managers that simplify the development process. By leveraging these components—Activity Manager, Content Providers, Telephony Manager, Location Manager, and Resource Manager—developers can create robust and responsive Android applications tailored to the needs of their users.

Dalvik Virtual Machine (DVM) in Android

The Dalvik Virtual Machine (DVM) is a specialized virtual machine used in the Android operating system, akin to the Java Virtual Machine (JVM) used in Java applications. However, DVM is specifically optimized for devices with limited memory and low-power CPUs, making it a better fit for mobile environments.

What Makes Dalvik Different from JVM?

Unlike the JVM, which executes .class files, the Dalvik Virtual Machine processes files with a .dex (Dalvik Executable) extension. These .dex files are automatically generated from .class files during the compilation process. They are highly optimized for efficient use of memory and processing power, making them ideal for mobile devices.

Advantages of Using Dalvik over JVM

1. Optimized for Low-Resource Environments
   • Dalvik is designed to operate efficiently on devices with limited memory and lower processing capabilities, making it well-suited for mobile devices.
2. Exclusive API Support
   • DVM can utilize Android’s specialized APIs along with certain core Java APIs, providing a tailored environment for Android application development.
3. Efficient Multitasking
   • Dalvik allows the creation of multiple instances simultaneously, which enhances security, provides better memory management, and supports multithreading. This leads to improved isolation of app processes, reducing the risk of interference between apps.

Core Java Libraries in Android

Android does not use the full Java Standard Edition (Java SE) or Java Micro Edition (Java ME) libraries. Instead, it relies on a set of Core Java Libraries specifically designed for Android. These libraries provide most of the standard functionalities of Java SE while being adapted to fit the constraints of mobile devices.

Key Features of Core Java Libraries in Android

• The core libraries offer familiar functions from the Java SE library, allowing developers to leverage existing Java knowledge.
• They are tailored for Android’s platform, providing optimized performance for mobile applications.

The Dalvik Virtual Machine and Core Java Libraries are integral to Android’s architecture, enabling efficient app execution on devices with limited resources. The DVM’s optimization and the tailored Core Java Libraries ensure that Android apps can run smoothly, even on devices with constrained hardware capabilities.