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

Chapter 12. Connecting Our Kotlin to the UI and Nullability

By the end of this chapter, the missing link between our Kotlin code and our XML layouts will be fully revealed, leaving us with the power to add all kinds of widgets and UI features to our layouts as we have done before, but this time we will be able to control them through our code.

In this chapter, we will take control of some simple UI elements, such as Button and TextView, and, in the next chapter, we will take things further and manipulate a whole range of UI elements.

To enable us to understand what is happening, we need to find out a bit more about the memory in an app, and two areas of it in particular – the Stack and the Heap.

In this chapter, we will cover the following topics:

  • Android UI elements are classes

  • Garbage collection

  • Our UI is on the Heap

  • More polymorphism

  • Nullability – val and var revisited

  • Casting to different types

Prepare to make your UI come to life.