[JAVA][Beginning Java 8 Games Development]

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Chapter 12 ■ Setting Boundaries for Your Action Figure in 2D: Using the Node Class LocalToParent Attribute Setting Screen Boundaries: .setBoundaries( ) Method The next most important thing to do for our InvinciBagel game is to make sure that the character does not disappear off the edge of the screen by placing a .setBoundaries() method call between the .setXYLocation() method, which evaluates arrow (or ASDW) keypress combinations, and increments the iX and iY Bagel object properties accordingly, and the .moveInvinciBagel() method, which actually executes the movement. By placing the .setBoundaries() method before the sprite movement is invoked, we can make sure that the sprite is not off the screen (and if he is, move him back onto the screen) before we actually call the move function (method). The first step in writing this code is to define the sprite size in pixels so that we can calculate this along with our WIDTH and HEIGHT Stage size constants to determine the boundary variable values that we will need to check our iX and iY sprite location against inside of the .setBoundaries() method and its conditional if() statement structures. As you can see in Figure 12-15, I define these sprite pixel size constant declarations at the top of the Bagel.java class, by using the following two lines of Java code: protected static final double SPRITE_PIXELS_X = 81; protected static final double SPRITE_PIXELS_Y = 81; Figure 12-15. Declare protected static final double SPRITE_PIXELS_X and SPRITE_PIXELS_Y constants at the top of class Next, we need to calculate the four screen boundary values using the WIDTH and HEIGHT constants in the InvinciBagel class and the SPRITE_PIXELS_X and SPRITE_PIXELS_Y constants we just defined at the top of this class. As you may have noticed from our 0,0 initial X,Y Bagel object location coordinates putting our sprite in the center of the screen, JavaFX is using a centered X axis and Y axis screen addressing paradigm. This means there are four quadrants, and that negative values (which mirror positive values) move left and up, and positive values move right and down. We can actually use this paradigm later on to quickly ascertain which quadrant of the screen the character is in. The way we would thus calculate the boundaries is to take half of the screen width and subtract half of the sprite width to find the right (positive) boundary value and simply take the negative of this for the value for the left boundary limit. A similar calculation applies to the top and bottom boundary value limit, for which we will take half of the screen height and subtract half of the sprite height to find the bottom (positive) boundary value and simply take the negative of this for the value for the top boundary limit value. The Java code for these calculations should look like the following: protected static final double rightBoundary = WIDTH/2 - SPRITE_PIXELS_X/2; protected static final double leftBoundary = -(WIDTH/2 - SPRITE_PIXELS_X/2); protected static final double bottomBoundary = HEIGHT/2 - SPRITE_PIXELS_Y/2; protected static final double topBoundary = -(HEIGHT/2 - SPRITE_PIXELS_Y/2); www.it-ebooks.info 267
Chapter 12 ■ Setting Boundaries for Your Action Figure in 2D: Using the Node Class LocalToParent Attribute As you can see in Figure 12-16, NetBeans is having trouble seeing the constants inside the InvinciBagel class. Figure 12-16. Hold a left arrow (or A) and up arrow (or W) key down at the same time, and move the Actor diagonally Mouse-over the wavy red error highlighting in NetBeans that is underneath the WIDTH constant, and select the import static invincibagel.InvinciBagel.WIDTH; option so that NetBeans will write this import statement for you. The industry standard way to “correctly” utilize import static (or static imports, if you wish) are for the import and use of constants, so we are in top conformance with Java programming standard procedures here. Perform that same work process again for the red error highlighting underneath the HEIGHT constant reference, and then add the .setBoundaries() method call in between the .setXYLocation() and .moveInvinciBagel() method calls in your .update() method. This would be done using the following Java method call in the .update() method, shown in Figure 12-17: setBoundaries(); Figure 12-17. Create rightBoundary, leftBoundary, bottomBoundary and topBoundary constants at the top of the class 268 www.it-ebooks.info
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Contents at a Glance About the Auth
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Introduction The Java Programming L
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■ Introduction In Chapter 13 you
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Chapter 1 ■ Setting Up a Java 8 G
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Chapter 2 Setting Up Your Java 8 ID
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Chapter 2 ■ Setting Up Your Java
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Profiling Your Java 8 Game Applicat
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Chapter 3 ■ A Java 8 Primer: An I
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Chapter 5 An Introduction to Game D
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Chapter 8 Creating Your Actor Engin
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Chapter 8 ■ Creating Your Actor E
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Chapter 9 Controlling Your Action F
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Chapter 9 ■ Controlling Your Acti
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Chapter 10 Directing the Cast of Ac
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Chapter 10 ■ Directing the Cast o
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Chapter 14 ■ Setting Up the Game
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Chapter 14 ■ Setting Up the Game
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Chapter 15 Implementing Game Audio
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Chapter 15 ■ Implementing Game Au
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Chapter 16 ■ Collision Detection:
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Chapter 17 Enhancing Game Play: Cre
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Chapter 17 ■ Enhancing Game Play:
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■ index Background image (cont.)
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■ index InvinciBagel animation (c
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■ index Modifier keywords access
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Beginning Java 8 Games Development
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This Java 8 Game Development book i
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■ Contents NetBeans 8.0 Is User I
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■ Contents ■■Chapter 5: An In
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■ Contents Creating a Hero Superc
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■ Contents Organizing the .update
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■ Contents Optimizing the Scene G
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About the Author Wallace Jackson ha
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Acknowledgments I would like to ack
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