Android Game Programming by Example

Table of Contents

Android Game Programming by Example

Credits

About the Author

About the Reviewers

www.PacktPub.com

Support files, eBooks, discount offers, and more

Why subscribe?

Free access for Packt account holders

Preface

What this book covers

What you need for this book

Who this book is for

Conventions

Reader feedback

Customer support

Downloading the example code

Downloading the color images of this book

Errata

Piracy

Questions

1. Player 1 UP

A closer look at the games

Tappy Defender

Tough retro platformer

Asteroids simulator

Setting up your development environment

Installing the JDK

Installing Android Studio

Summary

2. Tappy Defender – First Step

Planning the first game

Backstory

The game mechanics

Rules for the game

The design

Control

Model

View

Design pattern reality check

The game code structure

The Android Activity lifecycle

The Android Studio file structure

Building the home screen

Creating the project

What we did

Building the home screen UI

What we did

Coding the functionality

Creating GameActivity

What we did

Configuring the AndroidManifest.xml file

What we did

Coding the game loop

Building the view

Creating a new class for the view

What we did

Structuring the class code

The game activity

The PlayerShip object

Drawing the scene

Plotting and drawing

Drawing PlayerShip

The Canvas and Paint objects

Controlling the frame rate

Deploying the game

Debugging on an Android device

Summary

3. Tappy Defender – Taking Flight

Controlling the spaceship

Detecting touches

Adding boosters to the spaceship

Detecting the screen resolution

Building the enemies

Designing the enemy

Spawning the enemy

Making the enemy think

The thrill of flight – scrolling the background

Things that go bump – collision detection

Collision detection options

Rectangle intersection

Radius overlapping

The crossing number algorithm

Optimizations

Multiple hitboxes

Neighbor checking

Best options for Tappy Defender

Summary

4. Tappy Defender – Going Home

Displaying a HUD

Implementing the rules

Ending the game

Restarting the game

Adding sound FX

Generating the FX

The SoundPool class

Coding the sound FX

Adding persistence

Iteration

Multiple different enemy graphics

An exercise in balance

Format time

Handle the back button

The finished game

Summary

5. Platformer – Upgrading the Game Engine

The game

The backstory

The game mechanics

Rules for the game

Upgrading the game engine

The platform activity

Locking the layout to landscape

The PlatformView class

The basic structure of PlatformView

The GameObject class

The view through a viewport

Creating the levels

The enhanced update method

The enhanced draw method

Summary

6. Platformer – Bob, Beeps, and Bumps

The SoundManager class

Introducing Bob

Multiphase collision detection

Player input

Animating Bob

Summary

7. Platformer – Guns, Life, Money, and the Enemy

Ready aim fire

Pickups

The drone

The guard

Summary

8. Platformer – Putting It All Together

Bullet collision detection

Adding some fire tiles

Eye candy

The new platform tiles

The new scenery objects

Scrolling parallax backgrounds

Pause menu with moveable viewport

Levels and game rules

Traveling between levels

The level designs

The cave

The city

The forest

The mountains

The HUD

Summary

9. Asteroids at 60 FPS with OpenGL ES 2

Asteroids simulator

The game controls

Rules for the game

Introducing OpenGL ES 2

Why use it and how does it work?

What is neat about Version 2?

How we will use OpenGL ES 2?

Preparing OpenGL ES 2

Locking the layout to landscape

Activity

The view

A class to manage our game

Managing simple shaders

The game's main loop – the renderer

Building an OpenGL-friendly, GameObject super class

The spaceship

Drawing at 60 + FPS

Summary

10. Move and Draw with OpenGL ES 2

Drawing a static game border

Twinkling stars

Bringing the spaceship to life

Rapid fire bullets

Reusing existing classes

Adding the SoundManager class

Adding the InputController class

Drawing and moving the asteroids

Scores and the HUD

Adding control buttons

Tally icons

Life icons

Declaring, initializing, and drawing the HUD objects

Summary

11. Things That Go Bump – Part II

Planning for collision detection

Colliding with the border

The first phase of border collision detection

Colliding with an asteroid

The crossing number

The first phase and overview of asteroid collision detection

The CollisionPackage class

Adding collision packages to the objects and making them accessible

Adding a collision package to the Bullet class

Adding a collision package to the SpaceShip class

Adding a collision package to the Asteroid class

The CD class outline

Implementing radius overlapping for asteroids and ships

Implementing rectangle intersection for the border

Performing the checks

Helper methods

Destroying a ship

Destroying an asteroid

Testing for collisions in update()

Precise collision detection with the border

Precise collision detection with an asteroid

Finishing touches

Summary

Index

Android Game Programming by Example

Android Game Programming by Example

Copyright © 2015 Packt Publishing

All rights reserved. No part of this book may be reproduced, stored in a retrieval system, or transmitted in any form or by any means, without the prior written permission of the publisher, except in the case of brief quotations embedded in critical articles or reviews.

Every effort has been made in the preparation of this book to ensure the accuracy of the information presented. However, the information contained in this book is sold without warranty, either express or implied. Neither the author, nor Packt Publishing, and its dealers and distributors will be held liable for any damages caused or alleged to be caused directly or indirectly by this book.

Packt Publishing has endeavored to provide trademark information about all of the companies and products mentioned in this book by the appropriate use of capitals. However, Packt Publishing cannot guarantee the accuracy of this information.

First published: June 2015

Production reference: 1250615

Published by Packt Publishing Ltd.

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ISBN 978-1-78528-012-2

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Credits

Author

John Horton

Reviewers

Håvard Kindem

José Rodriguez-Rivas

Commissioning Editor

Nadeem N. Bagban

Acquisition Editor

Tushar Gupta

Content Development Editor

Siddhesh Salvi

Technical Editor

Prajakta Mhatre

Copy Editor

Charlotte Carneiro

Project Coordinator

Nidhi Joshi

Proofreader

Safis Editing

Indexer

Tejal Soni

Production Coordinator

Melwyn D'sa

Cover Work

Melwyn D'sa

About the Author

John Horton is a technology enthusiast based in the UK. When he is not creating apps and writing books or blog articles for http://www.gamecodeschool.com, he can be found playing or making video games with his two sons.

About the Reviewers

Håvard Kindem is a game developer from Norway who has a long-lived passion for games and game development. He started programming at an early age, which later resulted in an MSc in game technology. During his studies, Håvard became the founding member and CEO of Fallen Leaves Interactive, a group focusing on PC, Xbox, and Android development. The company made games for clients such as KLM Royal Dutch Airlines and contributed to Games4Health.

Currently, Håvard is employed at the National Lottery Association in Norway, where he works as a concept developer. In order to find new exciting products for its about 2.8 million customers, he has, among other things, worked on and published multiple mobile games. Håvard remains an avid gamer, and when he is not busy releasing a new project, he loves to return to the old classics or spend the evenings playing his bass guitar.

I would like to thank my mentor, Simon McCallum, for always challenging me and pushing me toward new technologies. I would also like to thank my nephew and niece for being my motivation and allowing me to stay a kid forever; I love you guys! Last but not least, I would like to thank my partner in crime, Sara, for her support and striving for perfection.

José Rodriguez-Rivas is a young game developer. He loves to dream big about his future, often picturing himself as a head developer for a huge game company that he started. He first started developing games using RPG Maker VX Ace when he was in the eighth grade. As soon as he got into high school, he wanted to learn how to actually program a video game. He first learned Java with the libGDX framework, which allows him to port his games to both PC and Android. He is really into web design as well, and has designed two websites, one for his own company, Tiny Country Games (https://tinycountrygames.com/), and another for the Young Entrepreneurs Association of California, YEACAL (http://yeacal.org/). He enjoys learning new things, even if they don't directly relate to game development. For example, he likes to practice instruments such as the guitar, ukulele, and electric bass.

First of all, I would thank my computer science teacher, Mark Sheinberg, for always pushing me to improve my coding skills and learn new things. I would like to thank my best friend, Charli-Anne Hanna-Baker, for always supporting my work and keeping my morale high with her amazing attitude. Annika Pašeta, thank you for giving me the opportunity of being the webmaster of YEACAL, which inspired me to learn ASP.NET and C#. Last but not least, I would like to thank my family for their constant support and love.

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Preface

Making games is addictive and very rewarding, it can be hard to stop once you get started. The problem comes when we reach a stumbling block because we don't know how to implement a feature, or perhaps integrate it into our game. This book is a whirlwind tour of as many Android 2D gaming features that can possibly be squeezed into 11 chapters.

Every line of the code used to build three games of increasing difficulty is shown in the text of the book and explained in a straightforward manner.

Steadily build up to implement a flexible and advanced game engine that uses OpenGL ES 2 for fast smooth frame rates. This is achieved by starting with a simple game and gradually increasing the complexity of the three complete games built step by step.

Implement cool features like sprite sheet character animation and scrolling parallax backgrounds. Design and implement genuinely challenging and playable platform game levels.

Learn to code both basic and advanced collision detection. Make simple the math behind 2D rotation, velocity, and collision. Run your game designs at 60 frames per second or better.

Process multi-touch screen input. Implement a multitude of other game features like pickups, firing weapons, HUDs, generating and playing sound FX, scenery, level transition, high scores, and more.

What this book covers

Chapter 1, Player 1 UP, is an introduction to the three cool games that we will build. We will also get the development environment set up.

Chapter 2, Tappy Defender – First Step, is about planning the game project and getting the code for our first game engine up and running. We will implement a main game loop, control the frame rate, and draw to the screen.

Chapter 3, Tappy Defender – Taking Flight, teaches us to add lots of new objects and some features like player controls, enemies, and scrolling stars in the background. In the Things that go bump – collision detection section, we will discuss our collision detection options and implement an efficient solution for this game.

Chapter 4, Tappy Defender – Going Home, completes the game, including adding high scores, victory conditions, sound FX, and more.

Chapter 5, Platformer – Upgrading the Game Engine, provides a good understanding of what is needed in a simple game engine. We can quickly learn about and build a more advanced and flexible engine, suitable for a really tough, retro 2D platform game.

Chapter 6, Platformer – Bob, Beeps, and Bumps, uses our new game engine to add a class to manage the sound FX and a class to implement the more complex player controls that are required by a game of this type. We can then make Bob, our playable character, an animated running, jumping hero.

Chapter 7, Platformer – Guns, Life, Money, and the Enemy, continues the subject of the previous two chapters; we add a ton of features in this one. We will add collectible pick-ups and power-ups, a deadly homing enemy, and a patrolling guard. Of course with all this, Bob is going to need a machine gun to defend himself, and he gets one!

Chapter 8, Platformer – Putting It All Together, is where our platform game comes to life. We will add lots of new platform tile types and scenery objects, multiple scrolling parallax backgrounds, collision detection, and a teleporting system so that Bob can travel between the levels of the game. Using our range of tile types, scenery objects, and backgrounds, we will implement four playable levels linked together by the teleporting system.

Chapter 9, Asteroids at 60 FPS with OpenGL ES 2, contains the final project of this book, which is an introduction to 2D games with the super fast OpenGL graphics library. In this chapter, we will quickly learn how to draw with OpenGL ES 2 and integrate the drawing system into our game engine. By the end of the chapter, we will have a working engine that draws an Asteroids-style spaceship to the screen.

Chapter 10, Move and Draw with OpenGL ES 2, is where we will quickly integrate our sound and control systems from the previous project. Then, we can add a game border, twinkling star system, spinning asteroids, a neat HUD, progressively difficult levels, and a rapid fire gun to the player's spaceship.

Chapter 11, Things That Go Bump – Part II, completes the Asteroids game by adding the collision detection. The math required to detect collisions with the irregularly-shaped spinning asteroids is made simple and implemented into the game engine. By the end of this chapter, you will have the third and final fully playable game.

What you need for this book

Any recent and free version of Eclipse or Android Studio running on any of the major operating systems can use the code in this book.

Android Studio is the recommended development tool, and at time of publication, the minimum system requirements are:

For Windows:

Microsoft Windows 8/7/Vista/2003 (32 or 64-bit)

2 GB RAM minimum, 4 GB RAM recommended

400 MB hard disk space

At least 1 GB for Android SDK, emulator system images, and caches

1280 x 800 minimum screen resolution

Java Development Kit (JDK) 7

Optional for accelerated emulator: Intel processor with support for Intel VT-x, Intel EM64T (Intel 64), and Execute Disable (XD) Bit functionality

For Mac OS X:

Mac OS X 10.8.5 or higher, up to 10.9 (Mavericks)

2 GB RAM minimum, 4 GB RAM recommended

400 MB hard disk space

At least 1 GB for Android SDK, emulator system images, and caches

1280 x 800 minimum screen resolution

Java Runtime Environment (JRE) 6

Java Development Kit (JDK) 7

Optional for accelerated emulator: Intel processor with support for Intel VT-x, Intel EM64T (Intel 64), and Execute Disable (XD) Bit functionality

On Mac OS, run Android Studio with Java Runtime Environment (JRE) 6 for optimized font rendering. You can then configure your project to use JDK 6 or JDK 7.

For Linux:

GNOME or KDE desktop

GNU C Library (glibc) 2.15 or later

2 GB RAM minimum, 4 GB RAM recommended

400 MB hard disk space

At least 1 GB for Android SDK, emulator system images, and caches

1280 x 800 minimum screen resolution

Oracle Java Development Kit (JDK) 7

Tested on Ubuntu 14.04, Trusty Tahr (64-bit distribution capable of running 32-bit applications).

Who this book is for

The book is best suited for existing Android or Java programmers, who want to adapt their skills to make exciting Android games.

The book is also for readers who might have no Android, game programming, or even Java experience, but a good understanding of object-oriented programming is assumed.

Also, a determined programming beginner with at least some OOP experience can follow along and build all the projects, because of the step-by-step approach of the book. This book will also be ideally suited for readers who have completed Learning Java By Building Android Games.

Conventions

In this book, you will find a number of text styles that distinguish between different kinds of information. Here are some examples of these styles and an explanation of their meaning.

Code words in text, database table names, folder names, filenames, file extensions, pathnames, dummy URLs, user input, and Twitter handles are shown as follows: We will first add all the classes, and then update LevelManager in the usual three places.

A block of code is set as follows:

if (lm.isPlaying()) {

  // Reset the players location as

  // the world centre of the viewport

  //if game is playing

  vp.setWorldCentre(lm.gameObjects.get(lm.playerIndex)

    .getWorldLocation().x,

    lm.gameObjects.get(lm.playerIndex)

    .getWorldLocation().y);

When we wish to draw your attention to a particular part of a code block, the relevant lines or items are set in bold:

    //Has player fallen out of the map?     if (lm.player.getWorldLocation().x < 0 ||       lm.player.getWorldLocation().x > lm.mapWidth ||       lm.player.getWorldLocation().y > lm.mapHeight) {

New terms and important words are shown in bold. Words that you see on the screen, for example, in menus or dialog boxes, appear in the text like this: In the Create New Project window shown next, we need to enter some basic information about our app.

Note

Warnings or important notes appear in a box like this.

Tip

Tips and tricks appear like this.

Reader feedback

Feedback from our readers is always welcome. Let us know what you think about this book—what you liked or disliked. Reader feedback is important for us as it helps us develop titles that you will really get the most out of.

To send us general feedback, simply e-mail <[email protected]>, and mention the book's title in the subject of your message.

If there is a topic that you have expertise in and you are interested in either writing or contributing to a book, see our author guide at www.packtpub.com/authors.

Customer support

Now that you are the proud owner of a Packt book, we have a number of things to help you to get the most from your purchase.

Downloading the example code

You can download the example code files from your account at http://www.packtpub.com for all the Packt Publishing books you have purchased. If you purchased this book elsewhere, you can visit http://www.packtpub.com/support and register to have the files e-mailed directly to you.

Downloading the color images of this book

We also provide you with a PDF file that has color images of the screenshots/diagrams used in this book. The color images will help you better understand the changes in the output. You can download this file from: https://www.packtpub.com/sites/default/files/downloads/0122OS_ColoredImages.pdf.

Errata

Although we have taken every care to ensure the accuracy of our content, mistakes do happen. If you find a mistake in one of our books—maybe a mistake in the text or the code—we would be grateful if you could report this to us. By doing so, you can save other readers from frustration and help us improve subsequent versions of this book. If you find any errata, please report them by visiting http://www.packtpub.com/submit-errata, selecting your book, clicking on the Errata Submission Form link, and entering the details of your errata. Once your errata are verified, your submission will be accepted and the errata will be uploaded to our website or added to any list of existing errata under the Errata section of that title.

To view the previously submitted errata, go to https://www.packtpub.com/books/content/support and enter the name of the book in the search field. The required information will appear under the Errata section.

Piracy

Piracy of copyrighted material on the Internet is an ongoing problem across all media. At Packt, we take the protection of our copyright and licenses very seriously. If you come across any illegal copies of our works in any form on the Internet, please provide us with the location address or website name immediately so that we can pursue a remedy.

Please contact us at <[email protected]> with a link to the suspected pirated material.

We appreciate your help in protecting our authors and our ability to bring you valuable content.

Questions

If you have a problem with any aspect of this book, you can contact us at <[email protected]>, and we will do our best to address the problem.

Chapter 1. Player 1 UP

The terminology used by old arcade and pinball machines 1 UP was a kind of notice to the players that they were playing (up) now. It was also used to indicate earning an extra life. Are you ready to build three great games?

We will build three cool games together. Every line of code for these three games is shown in this book; you will never have to refer to the code files to see what is going on. Also, the entire file set required to build all three games is included in the download bundle that can be obtained from the books page on the Packt website.

All the code, Android manifest files, and the graphical and audio assets are included in the download as well. The three cool games are progressively more challenging to implement.

The first project uses a simple but functional game engine that clearly demonstrates the essentials of a main game loop. The game will be fully working with the home screen, high scores, sound, and animation. But by the end of the project, as we add features and try to balance the game play, we will soon see that we need more flexibility in order to add features.

In the second project, a hard retro platformer, we will see how we can use a simple and flexible design to build a relatively fast and very flexible game engine, which is extendable and reusable. This flexibility will allow us to make quite a complex and well-featured game. This game will have multiple levels, different environments, and more. This in turn will highlight the need for being able to draw graphics more quickly. That leads us on to the third project.

In the third project, we will build an Asteroids-like game called Asteroids simulator. Although the game won't have as many features as the previous project, it will feature the super-smooth drawing of hundreds of animated game objects running at over 60 frames per second. We will achieve this by learning about and using the Open Graphics Library for Embedded Systems (OpenGL ES 2).

By the end of this book, you will have a whole repertoire of design ideas, techniques, and code templates that you can use in your future games. By seeing the strengths and weaknesses of the different ways of making games on Android, you will be able to successfully design and build games in the most appropriate way for your next big game.

A closer look at the games

Here is a quick glimpse at the three projects.

Tappy Defender

Fly Flappy Bird-style with one finger to reach your home planet, while avoiding multiple enemies. Features include:

Basic animation

Home screen

Collision detection

High scores

Simple HUD

One-finger touch screen controls

Tough retro platformer

This is a genuinely tough-to-beat retro style platform game. We have to guide Bob from the underground fire caves through the city, forest, and finally to the mountains. It has four challenging levels. Features include:

A more advanced, flexible game engine

More advanced sprite sheet character animation

A level builder engine to design your levels in text format

Multiple scrolling parallax backgrounds

Transition between levels

A more advanced HUD

Add loads of extra diverse levels

Sound manager to easily manage sound FX

Pickups

An upgradeable gun

Seek-and-destroy enemy drones

Simple AI scripting for patrolling enemy guards

Hazards such as fire pits

Scenery objects to create atmosphere

Asteroids simulator

This is a classic shooter with retro vector-graphics style visuals. It involves clearing waves of smoothly animated spinning asteroids with a rapid fire gun. Features include:

60 frames per second or better, even on old hardware

An introduction to OpenGL ES 2

Shooter with waves of progressive difficulty

Advanced multiphase collision detection

Setting up your development environment

All the code in this book and the download bundle will work in your favorite Android IDE. However, I found the latest version of Android Studio exceptionally friendly to use and the code was written and tested in it as well.

If you don't currently use Android Studio, I encourage you to give it a try. Here is a quick overview of how to get up and running quickly. This guide includes steps to install the Java JDK in case you are completely new to Android development.

Tip

If you already have your preferred development environment ready to go then jump straight to Chapter 2, Tappy Defender – First Step.

The first thing we need to do is prepare your PC to develop for Android using Java. Fortunately, this is made quite simple for us.

Tip

If you are learning on Mac or Linux everything in this book will still work. The next two tutorials have Windows-specific instructions and screenshots. However, it shouldn't be too difficult to vary the steps slightly to suit Mac or Linux.

All we need to do is:

Install the Java Development Kit (JDK), which allows us to develop in Java.

Then install Android Studio to make Android development fast and easy. Android Studio uses the JDK and some other Android-specific tools that get automatically installed when we install Android Studio.

Installing the JDK

The first thing we need to do is get the latest version of the JDK. To complete this guide, perform the following instructions:

We need to be on the Java website, so visit: http://www.oracle.com/technetwork/java/javase/downloads/index.html.

Find the three buttons shown here and click on the one that says JDK that is highlighted in the following image. They are on the right-hand side of the web page. Then, click on the Download button under the JDK option:

You will be taken to a page that has multiple options to download the JDK. In the Product/File Description column, you need to click the option that matches your operating system. Windows, Mac, Linux, and some other less common options are all listed.

A common question asked here is, do I have 32- or 64-bit windows? To find out, right-click on your My Computer icon (This PC on Windows 8), click on the Properties option, and look under the System heading at the System type entry:

Click on the somewhat hidden Accept License Agreement checkbox:

Now, click on download for your OS and type as previously determined. Wait for the download to finish.

In your downloads folder, double-click on the file you just downloaded. The latest version at the time of writing for a 64-bit Windows PC was jdk-8u5-windows-x64. If you are using Mac/Linux or have a 32-bit OS, your filename will vary accordingly.

In the first of several install dialogs, click on the Next button and you will see the following dialog box:

Accept