Book Image

Android Development with Kotlin

By : Igor Wojda, Marcin Moskala
Book Image

Android Development with Kotlin

By: Igor Wojda, Marcin Moskala

Overview of this book

Nowadays, improved application development does not just mean building better performing applications. It has become crucial to find improved ways of writing code. Kotlin is a language that helps developers build amazing Android applications easily and effectively. This book discusses Kotlin features in context of Android development. It demonstrates how common examples that are typical for Android development, can be simplified using Kotlin. It also shows all the benefits, improvements and new possibilities provided by this language. The book is divided in three modules that show the power of Kotlin and teach you how to use it properly. Each module present features in different levels of advancement. The first module covers Kotlin basics. This module will lay a firm foundation for the rest of the chapters so you are able to read and understand most of the Kotlin code. The next module dives deeper into the building blocks of Kotlin, such as functions, classes, and function types. You will learn how Kotlin brings many improvements to the table by improving common Java concepts and decreasing code verbosity. The last module presents features that are not present in Java. You will learn how certain tasks can be achieved in simpler ways thanks to Kotlin. Through the book, you will learn how to use Kotlin for Android development. You will get to know and understand most important Kotlin features, and how they can be used. You will be ready to start your own adventure with Android development with Kotlin.
Table of Contents (16 chapters)
Title Page
About the Authors
About the Reviewers
Customer Feedback
Making Your Marvel Gallery Application

Say hello to Kotlin

Kotlin is a modern, statically typed, Android-compatible language that fixes many Java problems, such as null pointer exceptions or excessive code verbosity. Kotlin is a language inspired by Swift, Scala, Groovy, C#, and many other languages. Kotlin was designed by JetBrains professionals, based on analysis of both developers experiences, best usage guidelines (most important are clean code and effective Java), and data about this language's usage. Deep analysis of other programming languages has been done. Kotlin tries hard to not repeat the mistakes from other languages and take advantage of their most useful features. When working with Kotlin, we can really feel that this is a mature and well-designed language.

Kotlin takes application development to a whole new level by improving code quality and safety and boosting developer performance. Official Kotlin support for the Android platform was announced by Google in 2017, but the Kotlin language has been here for some time. It has a very active community and Kotlin adoption on the Android platform is already growing quickly. We can describe Kotlin as a safe, expressive, concise, versatile, and tool-friendly language that has great interoperability with Java and JavaScript. Let's discuss these features:

  • Safety: Kotlin offers safety features in terms of nullability and immutability. Kotlin is statically typed, so the type of every expression is known at compile time. The compiler can verify that whatever property or method we are trying to access of a particular class instance actually exists. This should be familiar from Java which is also statically typed, but unlike Java, Kotlin type system is much more strict (safe). We have to explicitly tell the compiler whether the given variable can store null values. This allows making the program fail at compile time instead of throwing a NullPointerException at runtime:

  • Easy debugging: Bugs can be detected much faster during the development phase, instead of crashing the application after it is released and thus damaging the user experience. Kotlin offers a convenient way to work with immutable data. For example, it can distinguish mutable (read-write) and immutable (read-only) collections by providing convenient interfaces (under the hood collections are still mutable).
  • Conciseness: Most of the Java verbosity was eliminated. We need less code to achieve common tasks and thus the amount of boilerplate code is greatly reduced, even comparing Kotlin to Java 8. As a result, the code is also easier to read and understand (expressive).
  • Interoperability: Kotlin is designed to seamlessly work side by side with Java (cross-language project). The existing ecosystem of Java libraries and frameworks works with Kotlin without any performance penalties. Many Java libraries even Kotlin-specific versions that allow more idiomatic usage with Kotlin. Kotlin classes can also be directly instantiated and transparently referenced from Java code without any special semantics and vice versa. This allows us to incorporate Kotlin into existing Android projects and use Kotlin easily together with Java (if we want to).
  • Versatility: We can target many platforms, including mobile applications (Android), server-side applications (backend), desktop applications, frontend code running in the browser, and even build systems (Gradle).

Any programming language is only as good as its tool support. Kotlin has outstanding support for modern IDEs such as Android Studio, IntelliJ Idea, and Eclipse. Common tasks such as code assistance or refactoring are handled properly. The Kotlin team works hard to make the Kotlin plugin better with every single release. Most of the bugs are quickly fixed and many of the features requested by the community are implemented.


Kotlin bug tracker: slack channel:

Android application development becomes much more efficient and pleasant with Kotlin. Kotlin is compatible with JDK 6, so applications created in Kotlin run safely even on old Android devices that precede Android 4.

Kotlin aims to bring you the best of both worlds by combining concepts and elements from both procedural and functional programming. It follows many guidelines as described in the book, Effective Java, 2nd Edition, by Joshua Bloch, which is considered a must-read book for every Java developer.

On top of that, Kotlin is open sourced, so we can check out the project and be actively involved in any aspect of the Kotlin project such as Kotlin plugins, compilers, documentation, or the Kotlin language itself.