Book Image

Android Programming for Beginners - Second Edition

By : John Horton
Book Image

Android Programming for Beginners - Second Edition

By: John Horton

Overview of this book

Are you trying to start a career in programming, but haven't found the right way in? Do you have a great idea for an app, but don't know how to make it a reality? Or maybe you're just frustrated that in order to learn Android, you must know Java. If so, then this book is for you. This new and expanded second edition of Android Programming for Beginners will be your companion to create Android Pie applications from scratch. We will introduce you to all the fundamental concepts of programming in an Android context, from the basics of Java to working with the Android API. All examples use the up-to-date API classes, and are created from within Android Studio, the official Android development environment that helps supercharge your application development process. After this crash course, we'll dive deeper into Android programming and you'll learn how to create applications with a professional-standard UI through fragments and store your user's data with SQLite. In addition, you'll see how to make your apps multilingual, draw to the screen with a finger, and work with graphics, sound, and animations too. By the end of this book, you'll be ready to start building your own custom applications in Android and Java.
Table of Contents (35 chapters)
Android Programming for Beginners - Second Edition
Contributors
Preface
Other Books You May Enjoy
Index

Writing our first Java code


So, we now know the code that will output to logcat or the user's screen. But where do we put the code? To answer this question, we need to understand that the onCreate method in HelloWorldActivity.java executes as the app is preparing to be shown to the user. So, if we put our code at the end of this method, it will run just as the user sees it. Sounds good.

Note

We know that to execute the code in a method, we need to call it. We have wired our buttons up to call a couple of methods, topClick and bottomClick. Soon, we will write these methods. But who or what is calling onCreate? The answer to this mystery is that Android itself calls onCreate in response to the user clicking the app icon to run the app. In Chapter 6, The Android Lifecycle, we will look deeper, and it will be clear exactly what code executes and when. You don't need to completely comprehend this now. I just wanted to give you an overview of what was going on.

Let's quickly try this out. Switch...