[JAVA][Beginning Java 8 Games Development]

Chapter 9
Controlling Your Action Figure:
Implementing Java Event Handlers
and Using Lambda Expressions
Now that we have created the public abstract Actor and Hero classes, which I call the “actor engine,” in Chapter 8,
let’s get back into our InvinciBagel.java primary application class coding here in Chapter 9, and create the event
handling framework that we can use to control the primary hero for our game, the InvinciBagel himself. The event
handling that implements the interface between the player and your game programming logic could be looked at
as the “interactivity engine” for your game, if we follow the engine paradigm we have been using thus far. There
are many ways to interface with a game, including arrow keys (also known as a DPAD for consumer electronics
devices), the keyboard, a mouse or trackball, a game controller, touchscreen, or even advanced hardware,
such as gyroscopes and accelerometers. One of the choices you will make for your game development will be
how a player will interface with the game, using the hardware device they are playing the game on, and the input
capabilities it supports.
During this chapter, we will be doing a number of upgrades to your InvinciBagel.java class. The first is to add
support for the game WIDTH and HEIGHT variables in the form of Java constants. These will allow us to change the
width and height of the game play surface, which is the area inside of the game window that pops up, or the entire
screen, if your game player is using a consumer electronics device.
The second upgrade we will do is to add the Java code that will create a blank white screen for us to design the
game over (on top of) during the next several chapters. We’ll do this by installing a Color.WHITE background color
in the Scene() constructor method call (along with our new width and height variables), and then installing Java code
into our Button control event handler structure that are already in place, to hide the two ImageView “plates” we are
using for image compositing of our splash screen UI design. We can also use these two ImageView Node objects later
on to hold background imagery for our game play, once we get into that level of design. Remember it is important to
keep the number of Nodes in the Scene Graph to a minimum, so we will reuse Node objects, instead of adding more.
The third upgrade we’ll add is to add keyboard event handling routines to our Scene object that will handle the
arrow key support that we will use for the game, to span any hardware device that has an arrow key pad or DPAD. This
will handle any events at the top-level of the Scene down to the StackPane (Scene Graph) hierarchy. This will pass the
arrow key values pressed by the user to our Node objects. This will eventually allow motion control code to move the
actors around the game, which is something we will be getting involved with in greater detail in the next chapter.
Besides upgrading our InvinciBagel.java code, and adding keyboard event handling, we will also be learning
about lambda expressions during this chapter, just to make sure I get everything that is new in Java 8 covered during
this book. These lambda expressions are somewhat advanced to be covered in this beginner level book, but since they
are a major new feature of Java 8, and provide multi-threading support as well as more compact code structures, I am
going to cover them here in this chapter, partly because NetBeans 8 (no surprise here) is willing to code them for you!
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