Learn Sprite Kit for ios Game Development. Leland Long

Transcription

1 Learn Sprite Kit for ios Game Development Leland Long

2 Learn Sprite Kit for ios Game Development Copyright 2014 by Leland Long This work is subject to copyright. All rights are reserved by the Publisher, whether the whole or part of the material is concerned, specifically the rights of translation, reprinting, reuse of illustrations, recitation, broadcasting, reproduction on microfilms or in any other physical way, and transmission or information storage and retrieval, electronic adaptation, computer software, or by similar or dissimilar methodology now known or hereafter developed. Exempted from this legal reservation are brief excerpts in connection with reviews or scholarly analysis or material supplied specifically for the purpose of being entered and executed on a computer system, for exclusive use by the purchaser of the work. Duplication of this publication or parts thereof is permitted only under the provisions of the Copyright Law of the Publisher s location, in its current version, and permission for use must always be obtained from Springer. Permissions for use may be obtained through RightsLink at the Copyright Clearance Center. Violations are liable to prosecution under the respective Copyright Law. ISBN-13 (pbk): ISBN-13 (electronic): Trademarked names, logos, and images may appear in this book. Rather than use a trademark symbol with every occurrence of a trademarked name, logo, or image we use the names, logos, and images only in an editorial fashion and to the benefit of the trademark owner, with no intention of infringement of the trademark. The use in this publication of trade names, trademarks, service marks, and similar terms, even if they are not identified as such, is not to be taken as an expression of opinion as to whether or not they are subject to proprietary rights. While the advice and information in this book are believed to be true and accurate at the date of publication, neither the authors nor the editors nor the publisher can accept any legal responsibility for any errors or omissions that may be made. The publisher makes no warranty, express or implied, with respect to the material contained herein. Publisher: Heinz Weinheimer Acquisitions Editor: Michelle Lowman Development Editor: Gary Schwartz Technical Reviewer: Matthew Knott Editorial Board: Steve Anglin, Mark Beckner, Ewan Buckingham, Gary Cornell, Louise Corrigan, Jim DeWolf, Jonathan Gennick, Jonathan Hassell, Robert Hutchinson, Michelle Lowman, James Markham, Matthew Moodie, Jeff Olson, Jeffrey Pepper, Douglas Pundick, Ben Renow-Clarke, Dominic Shakeshaft, Gwenan Spearing, Matt Wade, Steve Weiss Coordinating Editor: Mark Powers Copy Editor: Kezia Endsley Compositor: SPi Global Indexer: SPi Global Artist: SPi Global Cover Designer: Anna Ishchenko Distributed to the book trade worldwide by Springer Science+Business Media New York, 233 Spring Street, 6th Floor, New York, NY Phone SPRINGER, fax (201) , orders-ny@springer-sbm.com, or visit Apress Media, LLC is a California LLC and the sole member (owner) is Springer Science + Business Media Finance Inc (SSBM Finance Inc). SSBM Finance Inc is a Delaware corporation. For information on translations, please rights@apress.com, or visit Apress and friends of ED books may be purchased in bulk for academic, corporate, or promotional use. ebook versions and licenses are also available for most titles. For more information, reference our Special Bulk Sales ebook Licensing web page at Any source code or other supplementary material referenced by the author in this text is available to readers at For detailed information about how to locate your book s source code, go to

3 To William Bill VanBelle For guiding a young computer science student toward all-things Apple

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5 Contents at a Glance About the Author...xiii About the Technical Reviewer... xv Acknowledgments... xvii Introduction... xix Chapter 1: Hello World...1 Chapter 2: SKActions and SKTextures: Your First Animated Sprite...13 Chapter 3: Sprite Movement Responding to User Inputs...29 Chapter 4: Edges, Boundaries, and Ledges...49 Chapter 5: More Animated Sprites: Enemies and Bonuses...77 Chapter 6: Creating a Cast of Characters Chapter 7: Points and Scoring Chapter 8: Contacts and Collisions Chapter 9: Add More Scenes and Levels Chapter 10: Where to Go from Here Index v

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7 Contents About the Author...xiii About the Technical Reviewer... xv Acknowledgments... xvii Introduction... xix Chapter 1: Hello World...1 We Love Games...1 Tradition...1 Setup...2 Summary...12 Chapter 2: SKActions and SKTextures: Your First Animated Sprite...13 Humble Beginnings...13 Removing Unnecessary Tidbits...14 Device Orientation...15 Slight View Controller Changes...16 More Unneeded Template Text...16 Images Available for Download...17 vii

8 viii Contents Background Color...18 The Splash Screen...18 Anchor Points...19 Back to the Splash Screen...20 Moving Between Scenes...20 Creating a New Scene...21 Animated Transitions Using SKActions...22 Grouping Multiple Actions...24 Animation Frames Using SKTextures...24 Summary...27 Chapter 3: Sprite Movement Responding to User Inputs...29 Run Away!...29 Code Reorganization...31 New Class for the Player...33 Replacing Static Values...36 New Class for Your Textures...37 Adding Textures...39 Changing Direction...41 Skidding to a Stop...44 Summary...48 Chapter 4: Edges, Boundaries, and Ledges...49 Physics...49 Properties of a Physics Body...50 Adding a Backdrop...51 Contacts and Collisions...51 Adding a Brick Base...54 Determining Contact with an Edge...56 Handling Sprite Wrapping...56

9 Contents ix Jumping...58 Ledges and Joints...66 Summary...75 Chapter 5: More Animated Sprites: Enemies and Bonuses...77 The Opposition...77 Optimizing Texture Generation...79 Enemy Ratz Class...80 Timing...84 Wrapping...85 The Update Method...86 Collisions...89 Bonus Coins...94 Enemy and Coin Collisions Summary Chapter 6: Creating a Cast of Characters Static vs. Dynamic Characters File Format XML Format Loading the File Parsing the Data Implementing a New Spawning Process Summary Chapter 7: Points and Scoring What s the Point? Score Display SKLabelNode Custom Font Textures Status Bar = Off...128

10 x Contents A Different Kind of Score Playing Sound Files CAF Audio Format Player Spawn Sound Effect Player Running Sound Effect Player Jumping Sound Effect Player Skidding Sound Effect Enemy Spawn Sound Effect Coin Spawn Sound Effect Summary Chapter 8: Contacts and Collisions Didn t You Cover this Already? Contacts vs. Collisions Grates Pipes Enemies that Occasionally Get Stuck Setting the Player s Starting Location Collecting Coins Coin-Collection Sound Effect Coin Collection Point Display Particle Effects Coin Contact from Below the Ledges Ratz Contact from Below the Ledges Intersection Not Sensitive Enough Base Runners Player Kicking Enemies Ratz Collection Sound Effect Ratz Collection Point Display...170

11 Contents xi Kicked Off Into the River Enemies Kill Player Player Death Sound Effect Player Falls Off Ledge Player in the Water Summary Chapter 9: Add More Scenes and Levels Multiple Player Lives Adding a Visual Life Meter Game Over High Score Level-Completion Test Level-Completion Effects Unending Levels A New Enemy Type Two Hits Instead of One Levels Three and Four Player Instructions Summary Chapter 10: Where to Go from Here Going Forward with Sprite Kit Making the Game Better Resources Farewell Index...227

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13 About the Author Leland Long s programming career began on a VIC-20 computer. He moved up to the Apple IIe and then on to the Mac 512, where he began using Lightspeed Pascal to write fancier and more complex games. As a hobbyist, Leland has written a few programs over the years in BASIC and Pascal, but he never pursued learning the more common languages (like C) or learning object-oriented concepts. The release of the iphone SDK changed that! Based on that event, Leland dove headfirst into learning all that he could about Objective-C and ios programming. He is currently an IT Director for a flooring installation company in South Carolina, where he lives with his youngest daughter. His oldest daughter and four grandchildren live close enough to keep life entertaining. xiii

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15 About the Technical Reviewer Matthew Knott has been writing code for as long as he can remember from marveling at moving pixels on a BBC Micro to writing ridiculous text adventures for his mother on an overheating ZX Spectrum 48k. Matthew has been a professional software developer for the past 12 years, six of which have been spent in the educational sector where he has now entered the sometimes-scary world of management (although when they see the mess he made of the budget, that won t last long). Matthew s work and hobbies are basically the same things, but when he s not working, he loves life in a beautiful part of Wales with his wife, Lisa, and two kids, Mikey and Charlotte. xv

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17 Acknowledgments This book could not have been written without the hard-working folks at Apress. Steve Anglin got the ball rolling and Michelle Lowman handled everything in the acceptance process. Louise Corrigan helped out when others were unavailable. Mark Powers kept the book on the right track, and Gary Schwartz helped with some terrific feedback along the way. To all of the fine employees at Apress: Thank you, thank you! A very special thanks goes out to Matthew Knott, the technical reviewer, who tested all of the code in the book and made sure that everything worked as described. xvii

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19 Introduction What This Book Is This book serves as a guide to help you make your own iphone game. The goal is to help you create a simple 2D game from scratch using the new programming framework provided by Apple called Sprite Kit. By using Sprite Kit to create your game, you will find that a lot of things that you would normally have to code yourself handled for you. You ll be amazed at how little code it takes to create animated characters (sprites) that can interact with each other as they move around the screen. As you work your way through this book, you will create a fairly simple (old-school style) 2D game for the iphone that allows users to control a character using their fingers on the touch screen. We ll add some bad guys to give the character certain challenges and some bonus items that users can collect for extra points. We won t deal with the complexity of screen scrolling (in order to keep it simple) and instead will use a stationary screen, adding ledges so that the character can have some more space in which to run around, rather than moving only along the bottom of the screen. Each chapter is designed to highlight specific Sprite Kit features and basic game development concepts, which will help you understand how to control or interact with those features and concepts. When you re finished with the book, you will have a broad understanding of what Sprite Kit is all about, and you will have a cool game to play when you take a break from coding your soon-to-be best-selling game. Why Buy This Book Why not just look through the awesome sample game called Adventure that Apple provides for Sprite Kit developers to explore and examine? Because it can be complex and difficult for beginners to dissect and understand. It is meant for more experienced game developers to use, so that they can take their existing knowledge and use the new Sprite Kit APIs (Application Programming Interface) to make their next game quicker and easier than ever before. I believe that less experienced developers need something more straightforward as their introduction to Sprite Kit. Start simple and move on to bigger and better game development once you understand the basics. xix

20 xx Introduction What You Need to Know This book assumes that you have a basic understanding of how to create applications for the iphone using Xcode. You will not be spending any time learning programming styles or skills. You will be focusing solely on making a game using Xcode as the tool. We assume that you can download, install, and use the latest version of Xcode to create an application and run it on the iphone Simulator. What You Need to Have In terms of hardware, you need an Intel-based Macintosh running Mountain Lion (OS X 10.8) or later. Regarding software, you need Xcode 5.0 or later, since that is the first version to include the Sprite Kit APIs. You can download Xcode from What s in This Book Here is a brief overview of the chapters in this book: nnin Chapter 1, you ll start with a template that gives you an intro screen and a main game screen that will serve as the foundation for everything else that you do with Spite Kit. nnin Chapter 2, you ll add some basic physics so that your character doesn t just float around the screen. Then you ll use some SKTextures for handling the graphical side of the animation and some SKActions for handling the timing and movement side of the animation. nnin Chapter 3, you ll work with user interaction to drive character movement. nnin Chapter 4, we introduce some ideas about how you add environmental objects with which your character can interact, like ledges to run along and boundaries so that you can handle screen wrapping. nnin Chapter 5, you ll add some bad guys and bonuses. We like bonuses! nnin Chapter 6, we ll present one way to create a sort of cast of characters that will handle the timing and spawning of bad guys and bonuses. You don t want everyone showing up on stage all at once! nnin Chapter 7, it s all about points, as in a score! It s all about the points, right?! nnin Chapter 8, you ll work with sprite interaction. You don t want your character just running around the screen, floating right through the enemies and obstacles, now do you? nnin Chapter 9, you ll add more levels. You want the game to get progressively harder as time goes on in order to keep it challenging and interesting, after all. nnin Chapter 10, we ll wrap things up and point you where you can go from here to make your game even more interesting and complex. With all of these technical details out of the way, let s get our hands dirty with some code! Turn the page already! :)