[JAVA][Beginning Java 8 Games Development]

Chapter 12
Setting Boundaries for Your Action
Figure in 2D: Using the Node Class
LocalToParent Attribute
Now that we have organized your Java code into logical methods in the InvinciBagel.java class, and wired up the
GamePlayLoop .handle() method to the Bagel .update() method in Chapter 10, to make sure that our KeyEvent
handlers will move our InvinciBagel character around the screen, it is time to establish some boundaries for our
game hero, so that he does not leave the field of play, so to speak. To do this, we will need to dive into the JavaFX Node
superclass at a much deeper level of detail then we did in Chapter 4. We will look at how transforms are performed,
and more important, how they function relative to the Parent Node, which is located above them in the Scene Graph.
For our Actor ImageView Node(s), that Parent Node would be the Scene Graph root StackPane Node.
Before we start getting into code complexities such as absolute or relative transformation, which we will be
looking at during this chapter, and things such as collision detection and physics simulation, which we will cover later
in Chapters 16 and 17, we will need to get back into our InvinciBagel.java primary application class Java code here in
Chapter 12, so that we can do a few more things that will optimize the Java 8 foundation for our game. We have been
putting our game engines into place during the first part of this book, and I want to make sure that everything is “up to
snuff” before I start to build complex code structures on top of what we have put into place so far. We’re going to make
sure everything is “locked down tightly!”
For this reason, I am going to spend the first few pages of this chapter getting rid of those import static Java
statements, which although they work just fine, as you have seen, they are not what is termed “best practice” in Java
programming. There is a more complex and involved way to talk between classes, involving a Java “this” keyword, so I
am going to show you how to implement far more private variables (and far less static variables), and then I will teach
you how to use reference objects, represented by the Java this keyword, to send object data variables between classes.
This is a somewhat advanced topic for a beginner level book, but it will allow you to write more professional
and “industry standard” Java 8 code, so it will be worth the extra effort. Sometimes, the right way to do things is more
involved and detailed than the basic (simple) way to get things coded. The assumption here is that you are going to be
producing a commercially viable game, so you will need a rock solid foundation to build increasingly complex code on.
After we finish adding additional code refinements in our InvinciBagel.java class, which will implement Java
“encapsulation” using private variables wherever possible, and the this keyword where needed to provide access to
the InvinciBagel object to other related classes—in this case, the GamePlayLoop and Bagel classes for now—we will
begin to add complexity to the sprite movement code that is in our Bagel class .update() method.
We will add code that will tell your InvinciBagel character where the ceiling and floor of his Scene and Stage are
located, and where the left and right sides of the screen are, so that he does not fall off of his flat 2D world. We will
also organize the methods in the Bagel.java class, so that the .update() method only calls higher-level methods that
contain all of the Java programming logic in an exceptionally well organized fashion.
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