Book Image

Android Studio 3.5 Development Essentials - Kotlin Edition

By : Neil Smyth
Book Image

Android Studio 3.5 Development Essentials - Kotlin Edition

By: Neil Smyth

Overview of this book

Popularity of Kotlin as an Android-compatible language keeps growing every day. This book will help you to build your own Android applications using Kotlin. Android Studio 3.5 Development Essentials Kotlin Edition first teaches you to install Android development and test environment on different operating systems. Next, you will create an Android app and a virtual device in Android studio, and install an Android application on emulators. You will test apps on physical android devices, then study Android Studio code editor, Android architecture, and the anatomy of an Android app. The focus then shifts to Kotlin language. You’ll get an overview of Kotlin language and practice converting code from Java to Kotlin. You’ll also explore Kotlin data types, operators, expressions, loops, functions, and the basics of OOP concept in Kotlin. This book will then cover Android Jetpack and how to create an example app project using ViewModel component, as well as advanced topics such as views and widgets implementation, multi-window support integration, and biometric authentication. Finally, you will learn to upload your app to the Google Play Console and handle the build process with Gradle. By the end of this book, you will have gained enough knowledge to develop powerful Android applications using Kotlin.
Table of Contents (93 chapters)
93
Index

16.12 Companion Objects

A Kotlin class can also contain a companion object. A companion object contains methods and variables that are common to all instances of the class. In addition to being accessible via class instances, these properties are also accessible at the class level (in other words without the need to create an instance of the class).

The syntax for declaring a companion object within a class is as follows:

class ClassName: ParentClass {

   // Properties

   // Methods

   companion object {

        // properties

        // methods

    }

}

To experience a simple companion object example in action, enter the following into the Kotlin online playground at https://try.kotl.in:

class MyClass {

   

    fun showCount() {

      ...