[JAVA][Beginning Java 8 Games Development]

Chapter 4 ■ An Introduction to JavaFX 8: Exploring the Capabilities of the Java 8 Multimedia Engine
You can assign an action to be executed when the animation has completed playback, using the onFinished
property loaded with an ActionEvent object. The action will be executed when the animation reaches the end of each
loop, and, as you can imagine, some very powerful things can be triggered in a game with this particular capability.
There are also read-only variables (properties), which you can “poll” at any time to find the status, currentTime,
currentRate, cycleDuration, and totalDuration for each Animation object. For example, you can use the currentTime
property to see the position of the playback head (frame pointer) at any point in time in the animation playback cycle.
The JavaFX TimeLine Class: An Animation Subclass for Property Timeline Management
The JavaFX Timeline class is a subclass of the JavaFX Animation superclass, so its inheritance hierarchy starts with the
Java 8 masterclass, java.lang.Object, progressing down to the Timeline class, as follows:
> java.lang.Object
> javafx.animation.Animation
> javafx.animation.Timeline
A Timeline object can be used to define a special kind of Animation object that is composed of JavaFX values
(properties) of the object type WritableValue. Because all JavaFX properties are of that type, this class can be used to
animate anything in JavaFX, which means that its use is limited only by your imagination.
As mentioned earlier, Timeline animations are defined using KeyFrame objects, created via the KeyFrame class,
which both creates and manages these objects. A KeyFrame object is processed by a Timeline object, according to a
time variable (accessed via KeyFrame.time) and properties to be animated, which are defined using the KeyFrame
object’s values variable (accessed via KeyFrame.values).
It is important to note that you need to set up your KeyFrame objects before you start running the Timeline
object, as you cannot change a KeyFrame object within a running Timeline object. This is because it is put into system
memory once it has been started. If you want to change a KeyFrame object in a running Timeline object in any way,
first, stop the Timeline object; then, make the change to the KeyFrame; and, finally, start the Timeline object again.
This will reload the Timeline object and its revised KeyFrame objects into memory with their new values.
The Interpolator class interpolates these KeyFrame.values in the Timeline object, based on the timeline
direction. Interpolation is a process of creating in-between (or tween) frames, based on the beginning and ending
values. In case you are wondering how the direction is inferred, it is kept in the rate and the read-only currentRate
property of the Animation superclass (which is a part of the extended Timeline subclass).
Inverting the value of the rate property (i.e., making it negative) will reverse (toggle) the playback direction; the
same principle holds when reading the currentRate property (a negative value signifies the reverse, or backward,
direction). Finally, the KeyValue class (object) is used to hold the values inside the KeyFrame object.
The JavaFX Transition Class: An Animation Subclass for Transition
Effects Application
The JavaFX Transition class is a subclass of the JavaFX Animation superclass, so its inheritance hierarchy starts with
the Java 8 masterclass, java.lang.Object, progressing down to the Transition class, as follows:
> java.lang.Object
> javafx.animation.Animation
> javafx.animation.Transition
The Transition class is a public abstract class, and, as such, it can only be used (subclassed or extended) to
create transition subclasses. In fact, ten of these subclasses have already been created for you to use to create your
own transition special effects; these are the SequentialTransition, FadeTransition, FillTransition, PathTransition,
PauseTransition, RotateTransition, ScaleTransition, TranslateTransition, ParallelTransition, and
StrokeTransition classes. As a subclass of Animation, the Transition class contains all the functionality of Animation.
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