Book Image

Learning Java by Building Android Games - Third Edition

By : John Horton
5 (1)
Book Image

Learning Java by Building Android Games - Third Edition

5 (1)
By: John Horton

Overview of this book

Android is one of the most popular mobile operating systems today. It uses the most popular programming language, Java, as one of the primary languages for building apps of all types. Unlike most other Android books, this book doesn’t assume that you have any prior knowledge of Java programming, instead helps you get started with building Android games as a beginner. This new, improved, and updated third edition of Learning Java by Building Android Games helps you to build Android games from scratch. Once you've got to grips with the fundamentals, the difficulty level increases steadily as you explore key Java topics, such as variables, loops, methods, object-oriented programming (OOP), and design patterns while working with up-to-date code and supporting examples. At each stage, you'll be able to test your understanding by implementing the concepts that you’ve learned to develop a game. Toward the end, you’ll build games such as Sub Hunter, Retro Pong, Bullet Hell, Classic Snake, and Scrolling Shooter. By the end of this Java book, you'll not only have a solid understanding of Java and Android basics but will also have developed five cool games for the Android platform.
Table of Contents (24 chapters)

Scope – methods and variables

If you declare a variable in a method, whether that is one of the Android methods such as onCreate or one of our own methods, it can only be used within that method.

It is no use doing this in the onCreate method:

int a = 0;

And then after, trying to do this in the newGame method or some other method:


We will get an error because a is only visible in the method it was declared in. At first, this might seem like a problem but perhaps surprisingly, it is actually very useful.

That is why we declared those variables outside of all the methods, just after the class declaration. Here they are again, as a reminder:

public class SubHunter extends Activity {
    // These variables can be "seen"
    // throughout the SubHunter class
    int numberHorizontalPixels;
    int numberVerticalPixels;
    int blockSize;