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

More Java Collections – Meet Java Hashmap


Java HashMaps are neat. They are part of the Java Collections, and they are a kind of cousin to ArrayList, which we will use in the Note to Self project during the next chapter. They basically encapsulate useful data storage techniques that would otherwise be quite technical for us to code successfully for ourselves.

I thought it would be worth taking a first look at HashMap on its own.

Suppose we want to store the data of lots of characters from a role-playing game, and each different character is represented by an object of type Character.

We could use some of the Java tools we already know about, such as arrays or ArrayList. However, Java HashMap is also like these things, but with HashMap we can give a unique key/identifier to each Character object and access any such object using that key/identifier.

Note

The term "hash" comes from the process of turning our chosen key/identifier into something used internally by the HashMap class. The process is...