Write More Robust and Maintainable Android Apps with Kotlin “Peter Sommerhoff takes a practical approach to teaching Kotlin by providing a larger set of code listings that demonstrate language features and by guiding readers through the development of two Android apps step by step. . . . Peter finds a good balance between what is essential and what can be left to readers, so this book is an efficient yet comprehensible source for starting programming with Kotlin.” –Bernhard Rumpe, Professor of Software Engineering, RWTH Aachen University The Kotlin language brings state-of-the-art programming techniques and constructs to Android development. Kotlin for Android App Development will help you rapidly understand Kotlin’s principles and techniques, apply Kotlin in production app development, integrate Kotlin with existing Java code, and plan a migration to Kotlin, if you choose. If you have at least basic programming experience (with any language), Peter Sommerhoff’s well-crafted overview and examples will help you get quickly up-to-speed with the Kotlin language, its constructs, and its advanced functional and object-oriented capabilities. Once you’ve mastered these foundations, Sommerhoff walks you through two complete app development projects, introducing best practices and emerging patterns for writing code that’s robust, concise, readable, and highly performant. Understand Kotlin’s goals, principles, advantages, design, and constructs Take full advantage of functional programming in the Kotlin environment Write more concise and reusable code using Kotlin’s object-oriented features Interoperate with existing Java code, and plan a migration to Kotlin Use coroutines to efficiently handle concurrency Capture data via third-party APIs, map it to internal data representations, and present it to users Master best practices for architecting Kotlin Android apps Improve productivity and readability by creating simple domain-specific languages in Kotlin Register your book for convenient access to downloads, updates, and/or corrections as they become available. See inside book for details.

Table of Contents:
Listings xiii Foreword xxvii Preface xxix Acknowledgments xxxii About the Author xxxiii Part I: Learning Kotlin 1 Chapter 1: Introducing Kotlin 3 What Is Kotlin? 3 Goals and Language Concepts 4 Why Use Kotlin on Android? 5 Kotlin versus Java 8 6 Tool Support and Community 7 Business Perspective 7 Who’s Using Kotlin? 8 Summary 9 Chapter 2: Diving into Kotlin 11 Kotlin REPL 11 Variables and Data Types 12 Conditional Code 15 Loops and Ranges 19 Functions 21 Null Safety 29 Equality Checks 32 Exception Handling 33 Summary 36 Chapter 3: Functional Programming in Kotlin 37 Purpose of Functional Programming 37 Functions 39 Lambda Expressions 40 Higher-Order Functions 41 Working with Collections 45 Scoping Functions 53 Lazy Sequences 61 Summary 67 Chapter 4: Object Orientation in Kotlin 69 Classes and Object Instantiation 69 Properties 70 Methods 80 Primary and Secondary Constructors 82 Inheritance and Overriding Rules 84 Type Checking and Casting 89 Visibilities 91 Data Classes 94 Enumerations 96 Sealed Classes 98 Objects and Companions 101 Generics 105 Summary 121 Chapter 5: Interoperability with Java 123 Using Java Code from Kotlin 123 Using Kotlin Code from Java 133 Best Practices for Interop 149 Summary 150 Chapter 6: Concurrency in Kotlin 151 Concurrency 151 Kotlin Coroutines 157 Summary 200 Part II: Kotlin on Android 203 Chapter 7: Android App Development with Kotlin: Kudoo App 205 Setting Up Kotlin for Android 205 App #1: Kudoo, a To-Do List App 210 Summary 239 Chapter 8: Android App Development with Kotlin: Nutrilicious 241 Setting Up the Project 242 Adding a RecyclerView to the Home Screen 243 Fetching Data from the USDA Nutrition API 250 Mapping JSON Data to Domain Classes 257 Introducing a ViewModel for Search 262 Letting Users Search Foods 265 Introducing Fragments I: The Search Fragment 268 Introducing Fragments II: The Favorites Fragment 276 Store User’s Favorite Foods in a Room Database 280 Fetching Detailed Nutrition Data from the USDA Food Reports API 288 Integrating the Details Activity 293 Storing Food Details in the Database 302 Adding RDIs for Actionable Data 307 Improving the User Experience 311 Summary 314 Chapter 9: Kotlin DSLs 315 Introducing DSLs 315 Creating a DSL in Kotlin 318 DSL for Android Layouts with Anko 328 DSL for Gradle Build Scripts 335 Summary 343 Chapter 10: Migrating to Kotlin 345 On Software Migrations 345 Leading the Change 346 Partial or Full Migration 349 Where to Start 351 Tool Support 354 Summary 356 Appendix A: Further Resources 359 Official Resources 359 Community 359 Functional Programming 360 Kotlin DSLs 360 Migrating to Kotlin 360 Testing 361 Glossary 363 Index 367