Book Image

How to Build Android Apps with Kotlin - Second Edition

By : Alex Forrester, Eran Boudjnah, Alexandru Dumbravan, Jomar Tigcal
5 (1)
Book Image

How to Build Android Apps with Kotlin - Second Edition

5 (1)
By: Alex Forrester, Eran Boudjnah, Alexandru Dumbravan, Jomar Tigcal

Overview of this book

Looking to kick-start your app development journey with Android 13, but don’t know where to start? How to Build Android Apps with Kotlin is a comprehensive guide that will help jump-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 with 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. You'll also get to grips with testing, learning how to keep your architecture clean, understanding how to persist data, and gaining 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 (24 chapters)
1
Part 1: Android Foundation
6
Part 2: Displaying Network Calls
12
Part 3: Testing and Code Structure
17
Part 4: Polishing and Publishing an App

Transforming LiveData

Sometimes, the LiveData you pass from the ViewModel to the UI layer needs to be processed first before displaying. For example, you can only select a part of the data or do some processing on it first. In the previous exercise, you filtered the data to only select popular movies from the current year.

To modify LiveData, you can use the Transformations class. It has two functions, Transformations.map and Transformations.switchMap, that you can use.

Transformations.map modifies the value of LiveData into another value. This can be used for tasks such as filtering, sorting, or formatting the data. For example, you can transform movieLiveData into string LiveData from the movie’s title:

private val movieLiveData: LiveData<Movie>
val movieTitleLiveData : LiveData<String> =
    Transformations.map(movieLiveData) { it.title }

When movieLiveData changes value, movieTitleLiveData will also change based on the movie’...