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As an application’s code base increases, it becomes harder for developers to maintain existing nid
features and introduce new ones. In this clean architecture book, you’ll learn to identify when and
A Architecture
how this problem emerges and how to structure your code to overcome it.
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The book starts by explaining clean architecture principles and Android architecture components h
and then explores the tools, frameworks, and libraries involved. You’ll learn how to structure your it
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application in the data and domain layers, the technologies that go in each layer, and the role that
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each layer plays in keeping your application clean. You’ll understand how to arrange the code t
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into these two layers and the components involved in assembling them. Finally, you’ll cover the
Take a layered approach to writing clean, testable,
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presentation layer and the patterns that can be applied to have a decoupled and testable c ode base. e
and decoupled Android applications
By the end of this architecture book, you’ll be able to build an application following clean
architecture principles and have the knowledge you need to maintain and test the application easily.
Things you will learn:
• Become well versed in the principles • Understand the role each layer plays in
behind clean architecture keeping the application clean
• Get to grips with writing loosely coupled • Integrate existing frameworks and
and testable code libraries for each layer
• Find out how to structure an application’s
code in separate layers
Alexandru Dumbravan
Foreword by Ed Price, Senior Program Manager in Architectural Publishing
Microsoft | Azure Architecture Center and Well-Architected Framework
Clean Android
Architecture
Take a layered approach to writing clean, testable,
and decoupled Android applications
Alexandru Dumbravan
BIRMINGHAM—MUMBAI
Clean Android Architecture
Copyright © 2022 Packt Publishing
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However, Packt Publishing cannot guarantee the accuracy of this information.
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First published: June 2022
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Published by Packt Publishing Ltd.
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ISBN 978-1-80323-458-8
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This book is dedicated to all the developers who went the extra mile to
learn, practice, hack, innovate, and then pass their knowledge on to
others. This propelled our development world forward and made this book
a possibility. This book is also dedicated to all the people in my life who
supported me through the times I was staring desperately at a computer
screen filled with compile errors.
Alexandru Dumbravan
Foreword
“If you think good architecture is expensive, try bad architecture.”
— Brian Foote, CEO of HUMBL
We know deep down that this statement is true. Poorly architected code can cause
problems in your application, but it can also make your code hard to understand,
navigate, be improved upon, and difficult to use for other developers.
“The glass is neither half empty nor half full. It’s simply larger than it needs to be.”
— Grace Hopper
Grace Hopper was an American computer scientist and Navy officer. She knew
the importance of a well-structured and clean architecture. They’re flexible, higher
performing, far more scalable, easier to test, and you can maintain them a lot faster and
more easily. A clean architecture is focused on getting the application layers built as
efficiently as possible, without leaving behind (as Grace might say) leftover cup.
In a mobile application, clean architecture is more important than ever. You might find
yourself battling against battery issues, memory consumption issues, security problems,
compatibility, or environmental changes. Your mobile application needs to truly achieve
portability.
In Clean Android Architecture, Alexandru Dumbravan applies his experience of developing
Android applications for over 10 years. He takes you through a quick tour of the core
software design principles and through the key features in the Android framework and
supporting libraries.
Next, you’ll dig deep in data sources. It’s vital to understand the libraries and frameworks
that are available for you to access and manage data. Then, Alexandru naturally transitions
into data presentation. How do you present data to the user? You’ll break down how the
user interface (UI) works and how to build your own UI solution.
Later, you’ll learn how to manage dependencies. Part of the value that Alexandru brings
to the book is that he shows you how these different challenges were handled in the past,
and what has changed over time. You’ll then see how to build the domain layer to sit in the
center of your application and to control your app logic. Next, you’ll build the data layer to
create and manage your data. The presentation layer handles the UI and the input/output.
Finally, you’ll put the modules together and test your application.
By building an Android application with a clean architecture, you’ll be able to put every
piece of your code to work, and you’ll end up with a far more scalable, performant, and
maintainable application. This is a book that you’ll want to come back to, to make sure
you’ve got each step of this process down. And once you do, well, we all know that the
present and future is in mobile applications. So, the question is, where are you taking us?
Ed Price
Senior Program Manager of Architectural Publishing
Microsoft, Azure Architecture Center (http://aka.ms/Architecture)
Co-Author of 7 Books, including Meg the Mechanical Engineer, The Azure Cloud Native
Architecture Mapbook (Packt), and ASP.NET Core 5 for Beginners (Packt)
Contributors
About the author
Alexandru Dumbravan has been an Android developer since 2011 and has worked across
a variety of Android applications that have contained features such as messaging, voice
calls, file management, and file management. He continues to broaden his development
skills while working in London for a popular fintech company.
About the reviewers
Revathi Gopalakrishnan is a software professional with 20 years of experience in the
IT industry. She has worked extensively in mobile application development and has led
various enterprise mobile enablement initiatives for large organizations and consumer
applications for customers around the globe. She is also interested in emerging areas,
such as machine learning, IoT, and robotic process automation. She has authored
a book with Packt titled Mobile Machine Learning. Revathi resides in Chennai and enjoys
spending her weekends with her husband and her two lovely daughters.
Jose Miguel is a software engineer who specializes in mobile development, with 5 years
of experience. He has an Android associate developer certification from Google.
He is also involved in the start-up tech community as a mentor in the OpenLab Peru
community, bringing guidance to new Android developers and entrepreneurs who
want to gain certain expertise in the mobile world. He resides in Lima, Peru, and enjoys
watching movies, reading comics, boxing, traveling, and learning about new cultures and
people around the world.
Table of Contents
Preface
Part 1 – Introduction
1
Getting Started with Clean Architecture
Technical requirements 4 The Gradle build system 20
The architecture of a legacy app 4 Networking 21
Humble objects 21
Legacy analysis 11
Functional paradigms 22
Software design principles 13 Kotlin adoption 22
SOLID principles 14 Dependency injection 23
Component cohesion principles 15 Android architecture components 23
Component coupling principles 16 Coroutines and flows 24
Jetpack Compose 25
Exploring the evolution
of Android 18 Enter clean architecture 31
Fragments 18 Summary 40
2
Deep Diving into Data Sources
Technical requirements 42 Using OkHttp and Retrofit
Understanding Kotlin for networking 58
coroutines and Flows 42 Exercise 02.03 – Using OkHttp and
Retrofit 63
Kotlin coroutines 46
Exercise 02.01 – Using Kotlin coroutines 48 Using the Room library
Kotlin Flows 54 for data persistence 69
Exercise 02.02 – Using Kotlin Flows 56
