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

Top-level functions

Another thing we can observe in a simple Hello, World! program is that the main function is not located inside any class. In Chapter 2, Laying a Foundation, we already mentioned that Kotlin can define various entities at the top level. A function that is defined at the top level is called a top-level function. Here is an example of one of them:

    // Test.kt 
    package com.example 
    fun printTwo() { 

Top-level functions can be used all around the code (assuming that they are public, which is the default visibility modifier). We can call them in the same way as functions from the local context. To access a top-level function, we need to explicitly import it into a file by using the import statement. Functions are available in the code hint list in Android Studio, so imports are automatically added when a function is selected (used). As an example, let's see a top-level function defined in Test.kt and use it inside the Main.kt file: