Book Image

How to Build Android Apps with Kotlin

By : Alex Forrester, Eran Boudjnah, Alexandru Dumbravan, Jomar Tigcal
Book Image

How to Build Android Apps with Kotlin

By: Alex Forrester, Eran Boudjnah, Alexandru Dumbravan, Jomar Tigcal

Overview of this book

Are you keen to get started building Android 11 apps, but don’t know where to start? How to Build Android Apps with Kotlin is a comprehensive guide that will help kick-start your Android development practice. This book starts with the fundamentals of app development, enabling you to utilize Android Studio and Kotlin to get started building Android projects. You'll learn how to create apps and run them on virtual devices through guided exercises. Progressing through the chapters, you'll delve into Android’s RecyclerView to make the most of lists, images, and maps, and see how to fetch data from a web service. Moving ahead, you'll get to grips with testing, learn how to keep your architecture clean, understand how to persist data, and gain basic knowledge of the dependency injection pattern. Finally, you'll see how to publish your apps on the Google Play store. You'll work on realistic projects that are split up into bitesize exercises and activities, allowing you to challenge yourself in an enjoyable and attainable way. You'll build apps to create quizzes, read news articles, check weather reports, store recipes, retrieve movie information, and remind you where you parked your car. By the end of this book, you'll have the skills and confidence to build your own creative Android applications using Kotlin.
Table of Contents (17 chapters)
Preface
12
12. Dependency Injection with Dagger and Koin

ViewModel and LiveData

Both ViewModel and LiveData represent specialized implementations of the life cycle mechanisms. They come in handy in situations where you want to keep your data saved when the screen rotates and when you want your data to be displayed only when the Views are available, thus avoiding one of the most common issues developers face – a NullPointerException – when trying to update a View. A good use of this is when you want to display the live score of your favorite team's game and the current minute of the game.

ViewModel

The ViewModel component is responsible for holding and processing data required by the UI. It has the benefit of surviving configuration changes that destroy and recreate fragments and activities, which allows it to retain the data that can then be used to re-populate the UI. It will be eventually destroyed when the activity or fragment will be destroyed without being recreated or when the application process is terminated...