book

Learning Java by Building Android Games - Third Edition

by John Horton

March 2021

Beginner to intermediate

686 pages

13h 6m

English

Packt Publishing

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Third EditionContributorsAbout the authorAbout the reviewer
Who this book is forWhat this book coversTo get the most out of this bookDownload the example code filesConventions usedGet in touchReviews
Technical requirementsWindowsMacLinuxWhat's new in the third edition?Why Java, Android, and games?The Java stumbling blockThe games we will buildSub' HunterPongBullet HellSnake CloneScrolling ShooterHow Java and Android work togetherRun that by me again – what, exactly, is Android?Setting up Android StudioStarting the first project – Sub' HunterAndroid Studio and our project – a very brief guided tourThe Project panelThe Editor windowRefactoring MainActivity to SubHunterLocking the game to full screen and landscape orientationAmending the code to use the full screen and the best Android classDeploying the game so farRunning the game on an Android emulatorRunning the game on a real deviceSummary
Planning the Sub' Hunter gameThe actions flowchart/diagramMapping out our code using commentsIntroducing Java methodsOverriding methodsStructuring Sub' Hunter with methodsIntroducing OOPClasses and objectsClasses, objects, and instancesA final word on OOP, classes, and objects – for nowUsing Java packagesAdding classes by importing packagesLinking up our methodsSummary
Handling syntax and jargonJava variablesDifferent types of variablesHow to use variablesDeclaring variablesInitializing variablesMaking variables useful with operatorsMost used operators in this bookDeclaring and initializing the Sub' Hunter variablesPlanning the variablesDeclaring the variablesHandling different screen sizes and resolutions Handling different screen resolutions, part 1 – initializing the variablesErrors, warnings, and bugsPrinting debugging informationTesting the gameSummary
MethodsMethods revisited and explained furtherMethod overloading by exampleCreating a new projectCoding the method overloading mini-appRunning the method overloading mini-appScope – methods and variablesMethod recursionRevisiting the code and methods we have used alreadyGenerating random numbers to deploy a subThe Random class and the nextInt method Testing the gameSummary
Understanding the Canvas classGetting started drawing with Bitmap, Canvas, and ImageViewUsing the Canvas classPreparing the objects of classesInitializing the objectsSetting the Activity contentCanvas Demo appCreating a new projectAndroid coordinate systemPlotting and drawingDrawing the Sub' Hunter graphics and textPreparing to drawInitializing Canvas, Paint, ImageView, and Bitmap objectsDrawing some gridlinesDrawing the HUDUpgrading the printDebuggingText methodSummary
Making decisions with JavaKeeping things tidyMore operatorsJava loopsWhile loopsDo while loopsFor loopsUsing for loops to draw the Sub' Hunter gridSummary
If they come over the bridge, shoot themElse do this insteadSwitching to make decisionsSwitch exampleCombining different control flow blocksUsing the continue keywordMaking sense of screen touchesCoding the onTouchEvent methodFinal tasksCoding the takeShot methodExplaining the takeShot methodCoding the boom methodDrawing the shot on the gridRunning the gameSummary
Basic object-oriented programmingHumans learn by doing Introducing OOPWhy do we do it like this?Class recapLooking at the code for a classClass implementationDeclaring, initializing, and using an object of the classBasic classes mini-appCreating your first classMore things we can do with our first classEncapsulationControlling class use with access modifiersControlling variable use with access modifiersMethods have access modifiers tooAccessing private variables with getters and settersSetting up our objects with constructorsUsing "this"Static methodsEncapsulation and static methods mini-appOOP and inheritanceInheritance mini-appPolymorphismAbstract classesInterfacesStarting the Pong gamePlanning the Pong gameSetting up the Pong projectRefactoring MainActivity to PongActivityLocking the game to fullscreen and landscape orientationAmending the code to use the full screen and the best Android classSummary

Coding the PongActivity classCoding the PongGame classThinking ahead about the PongGame classAdding the member variablesCoding the PongGame constructorCoding the startNewGame methodCoding the draw methodUnderstanding the draw method and the SurfaceView classThe game loopGetting familiar with threadsProblems with threadsJava try-catch exception handlingImplementing the game loop with a threadImplementing Runnable and providing the run methodCoding the threadStarting and stopping the threadThe activity lifecycleA simplified explanation of the Android lifecycleLifecycle phases – what we need to knowLifecycle phases – what we need to doUsing the activity lifecycle to start and stop the threadCoding the run methodRunning the gameSummary
The Ball classCommunicating with the game engineRepresenting rectangles and squares with RectFCoding the variablesCoding the Ball constructorCoding the RectF getter methodCoding the Ball update methodCoding the Ball helper methodsCoding a realistic-ish bounce Using the Ball classThe Bat classCoding the Bat variablesCoding the Bat constructorCoding the Bat helper methodsCoding the Bat's update methodUsing the Bat classCoding the Bat input handlingRunning the gameSummary
Handling collisionsCollision detection optionsOptimizing the detection methodsBest options for PongThe RectF intersects method Handling different versions of AndroidDetecting the current Android versionThe SoundPool classInitializing SoundPool the new way Generating sound effectsAdding sound to the Pong gameAdding the sound variablesInitializing the SoundPoolCoding the collision detection and playing soundsThe bat and the ballThe four wallsPlaying the gameSummary
Planning the projectStarting the projectRefactoring MainActivity to BulletHellActivityLocking the game to full-screen and landscape orientationAmending the code to use the full screen and the best Android classCreating the classesReusing the Pong engineCoding the BulletHellActivity class Coding the BulletHellGame classTesting the Bullet Hell engineCoding the Bullet classSpawning a bulletGetting started with Java arraysArrays are objectsSimple array example mini-appGetting dynamic with arraysDynamic array exampleEntering the nth dimension with arraysMultidimensional array mini appArray out of bounds exceptionsSpawning an array of bulletsRunning the gameSummary
The Bob (player's) classAdd the Bob graphic to the projectCoding the Bob classUsing the Bob classCoding the spawnBullet method (again)Running the gameThe Android Studio Profiler toolSummary
Managing and understanding memoryVariables revisitedIntroduction to the Snake gameLooking ahead to the Snake gameGetting started with the Snake gameRefactoring MainActivity to SnakeActivityLocking the game to fullscreen and landscape orientationAdding some empty classesCoding SnakeActivityAdding the sound effectsCoding the game engineCoding the membersCoding the constructorCoding the newGame methodCoding the run methodCoding the updateRequired methodCoding the update methodCoding the draw methodCoding the OnTouchEvent methodCoding pause and resumeRunning the gameSummary
Making the Snake game Spanish, English, or GermanAdding Spanish supportAdding German supportAdding the string resourcesAmending the Java codeRunning the game in German or SpanishSummary
Adding the graphicsCoding the Apple classThe Apple constructorUsing the Apple classRunning the gameUsing arrays in the Snake gameUnderstanding ArrayList classThe enhanced for loopArrays and ArrayLists are polymorphicIntroducing enumerationsSummary
Rotating BitmapsWhat is a Bitmap exactly?The Matrix classAdding the sound to the projectCoding the Snake classCoding the constructorCoding the reset methodCoding the move methodCoding the detectDeath methodCoding the checkDinner methodCoding the draw methodCoding the switchHeading methodUsing the snake class and finishing the gameRunning the completed gameSummary
Introducing the Scrolling Shooter projectGame programming patterns and the structure of the Scrolling Shooter projectStarting the projectRefactoring MainActivity to GameActivityLocking the game to fullscreen and landscape orientationCoding the GameActivity classGetting started on the GameEngine classControlling the game with a GameState class Passing GameState from GameEngine to other classesCommunicating from GameState to GameEngineGiving partial access to a class using an interfaceInterface refresherWhat we will do to implement the interface solutionCoding the GameState classSaving and loading the high score foreverPressing the "special button" – calling the method of the interfaceFinishing off the GameState classUsing the GameState classBuilding a sound engineAdding the sound files to the projectCoding the SoundEngine classUsing the SoundEngine classTesting the game so farBuilding a HUD class to display the player's control buttons and textCoding the prepareControls methodCoding the draw method of the HUD classCoding drawControls and getControlsBuilding a Renderer class to handle the drawingUsing the HUD and Renderer classesRunning the gameSummary
The Observer patternThe Observer pattern in the Scrolling Shooter projectCoding the Observer pattern in Scrolling ShooterCoding the Broadcaster interfaceCoding the InputObserver interfaceMaking GameEngine a broadcasterCoding a multitouch UI controller and making it a listenerCoding the required handleInput methodUsing UIControllerRunning the gameImplementing a particle system explosionCoding the Particle classCoding the ParticleSystem classAdding a particle system to the game engine and drawing it with the Renderer classBuilding a physics engine to get things movingRunning the gameSummary
Meeting the game objectsA reminder of how all these objects will behaveThe Entity-Component patternWhy lots of diverse object types are hard to manageThe first coding nightmareUsing a generic GameObject for better code structureComposition over inheritanceThe Simple Factory patternAt last, some good newsSummary so farThe object specificationsCoding the ObjectSpec parent classCoding all the specific object specificationsCoding the component interfacesGraphicsComponentInputComponentMovementComponentSpawnComponentCoding the player's and the background's empty component classesStdGraphicsComponentPlayerMovementComponentPlayerSpawnComponentPlayerInputComponent and the PlayerLaserSpawner interfaceLaserMovementComponentLaserSpawnComponentBackgroundGraphicsComponentBackgroundMovementComponentBackgroundSpawnComponentEvery GameObject has a transformEvery object is a GameObjectCompleting the player's and the background's componentsThe player's componentsCoding a scrolling backgroundGameObject/Component reality checkBuilding the GameObjectFactory classCoding the Level classPutting everything togetherUpdating GameEngineUpdating PhysicsEngineUpdating the rendererRunning the gameSummary
Adding the alien's componentsAlienChaseMovementComponentAlienDiverMovementComponentAlienHorizontalSpawnComponentAlienPatrolMovementComponentAlienVerticalSpawnComponentSpawning the aliensUpdating the GameEngine classUpdating the Level classUpdating the GameObjectFactory classRunning the gameDetecting collisionsRunning the completed gameSummary
PublishingUsing the assets from the bookFuture learningMy other channelsThanks
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Content preview from Learning Java by Building Android Games - Third Edition

Chapter 12: Handling Lots of Data with Arrays

In this chapter, we will first get the Bullet Hell project set up and ready to roll with a single bullet whizzing across the screen. Then we will learn about Java arrays, which allow us to manipulate a potentially huge amount of data in an organized and efficient manner.

Once we are comfortable handling arrays of data, we will see how we can spawn hundreds or thousands of our new Bullet class instances, without breaking a sweat.

The topics in this chapter are as follows: