Book Image

Android Programming with Kotlin for Beginners

By : John Horton
5 (1)
Book Image

Android Programming with Kotlin for Beginners

5 (1)
By: John Horton

Overview of this book

Android is the most popular mobile operating system in the world and Kotlin has been declared by Google as a first-class programming language to build Android apps. With the imminent arrival of the most anticipated Android update, Android 10 (Q), this book gets you started building apps compatible with the latest version of Android. It adopts a project-style approach, where we focus on teaching the fundamentals of Android app development and the essentials of Kotlin by building three real-world apps and more than a dozen mini-apps. The book begins by giving you a strong grasp of how Kotlin and Android work together before gradually moving onto exploring the various Android APIs for building stunning apps for Android with ease. You will learn to make your apps more presentable using different layouts. You will dive deep into Kotlin programming concepts such as variables, functions, data structures, Object-Oriented code, and how to connect your Kotlin code to the UI. You will learn to add multilingual text so that your app is accessible to millions of more potential users. You will learn how animation, graphics, and sound effects work and are implemented in your Android app. By the end of the book, you will have sound knowledge about significant Kotlin programming concepts and start building your own fully featured Android apps.
Table of Contents (33 chapters)
Android Programming with Kotlin for Beginners
Contributors
Preface
Index

Coding the MainActivity class


Let's get started with coding the Activity-based class. As usual, the class is called MainActivity, and it was autogenerated for us when we created the project.

Edit the class declaration and add the first part of the code for the MainActivity class:

import android.app.Activity
import android.os.Bundle
import android.graphics.Point

class MainActivity : Activity() {

    private lateinit var liveDrawingView: LiveDrawingView

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)

        val display = windowManager.defaultDisplay
        val size = Point()
        display.getSize(size)

        liveDrawingView = LiveDrawingView(this, size.x)

        setContentView(liveDrawingView)

    }
}

The preceding code shows several errors that we will talk about shortly. The first thing to note is that we are declaring an instance of our LiveDrawingView class. Currently, this is an empty class:

private lateinit var liveDrawingView...