[JAVA][Beginning Java 8 Games Development]

Chapter 9 ■ Controlling Your Action Figure: Implementing Java Event Handlers and Using Lambda Expressions
Adding Keyboard Event Handling: Using KeyEvents
I think that is enough background information for us to move on to implementing KeyEvent processing for the game,
so add a line of code after your screen WIDTH and HEIGHT constant declarations, and declare four Boolean variables
named up, down, left, and right, using a single compound declaration statement, shown in Figure 9-9. Since the
default value for any Boolean value is false (which will signify a key which is not being pressed, that is, a key which is
currently released), we do not have to explicitly initialize these variables. This is done by using the following line of
Java code, which is also shown error-free at the top of Figure 9-9:
boolean up, down, left, right;
Figure 9-9. Add a .setOnKeyPressed() function call off a scene object and create a new EventHandler object
As you can see at the bottom of Figure 9-9, I put the foundation for my KeyEvent (pressed) handling using the
.setOnKeyPressed() method call off of the Scene object named scene, which I have instantiated in the previous line of
code. Inside of this method call I create a new EventHandler just like we did for our action events.
The code, which as you can see has an error message attached to it until you import a KeyEvent class, looks like this:
scene.setOnKeyPressed(new EventHandler() { your .handle() method will go in here });
Use an Alt-Enter work process to select an import javafx.scene.input.KeyEvent option seen in Figure 9-9, to
remove this error message. Next, let’s take a look at the .handle() method we need to write to process the KeyEvent.
www.it-ebooks.info
199