Book Image

Learning Java by Building Android Games - Second Edition

By : John Horton
Book Image

Learning Java by Building Android Games - Second Edition

By: John Horton

Overview of this book

Android is one of the most popular mobile operating systems presently. It uses the most popular programming language, Java, as the primary language for building apps of all types. However, this book is unlike other Android books in that it doesn’t assume that you already have Java proficiency. This new and expanded second edition of Learning Java by Building Android Games shows you how to start building Android games from scratch. The difficulty level will grow steadily as you explore key Java topics, such as variables, loops, methods, object oriented programming, and design patterns, including code and examples that are written for Java 9 and Android P. At each stage, you will put what you’ve learned into practice by developing a game. You will build games such as Minesweeper, Retro Pong, Bullet Hell, and Classic Snake and Scrolling Shooter games. In the later chapters, you will create a time-trial, open-world platform game. By the end of the book, you will not only have grasped Java and Android but will also have developed six cool games for the Android platform.
Table of Contents (30 chapters)
Learning Java by Building Android Games Second Edition
Contributors
Preface
Index

Drawing the Sub' Hunter graphics and text


Now we can use everything we have learned about Canvas and the Android coordinate system to get started drawing our game. We will meet another method of the Canvas class called drawLine. Unsurprisingly this will be used to draw the grid lines.

We will, however, stumble upon a slight problem to do with the practicality of drawing so many lines.

We will also draw the HUD text and the debugging text.

Preparing to draw

Add the declaration of all the graphics related reference variables we will need. The new code is highlighted amongst the previous code.

public class SubHunter extends Activity {

    // These variables can be "seen"
    // throughout the SubHunter class
    int numberHorizontalPixels;
    int numberVerticalPixels;
    int blockSize;
    int gridWidth = 40;
    int gridHeight;
    float horizontalTouched = -100;
    float verticalTouched = -100;
    int subHorizontalPosition;
    int subVerticalPosition;
    boolean hit = false;
    int shotsTaken...