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

Using the Canvas class


Let's take a look at the code and the different stages that are required to get drawing, then we can quickly move on to drawing something, for real, with the Canvas demo app.

Preparing the instances of the required classes

The first step is to turn the classes that we need into usable instances.

First, we declare all the instances that we require. We can't initialize the instances right away, but we can make sure that we initialize them before they are used, so we use lateinit in the same way we did in the Animation demo app:

// Here are all the objects(instances)
// of classes that we need to do some drawing
lateinit var myImageView: ImageView
lateinit var myBlankBitmap: Bitmap
lateinit var myCanvas: Canvas
lateinit var myPaint: Paint

The previous code declares references of the ImageView, Bitmap, Canvas, and Paint types. They are named myImageView, myBlankBitmap, myCanvas, and myPaint, respectively.

Initializing the objects

Next, we need to initialize our new objects before...