Heaven acts with vitality and persistence.
In correspondence with this
The superior person keeps himself vital without ceasing.
—I Ching
You downloaded the JavaFX 2.0 SDK and the JavaFX plugin for Netbeans. You wrote and ran your first JavaFX 2.0 GUI programs. You learned the fundamental building blocks of JavaFX 2.0: the Stage and Scene classes, and the Nodes that go into the Scene. And you have no doubt noticed the use of user-defined model classes to represent the application state and have that state communicated to the UI through properties and bindings.
In this topic, we give you a guided tour of the JavaFX 2.0 properties and bindings framework. After recalling a little bit of history and presenting a motivating example that shows various ways that a JavaFX 2.0 Property can be used, we cover key concepts of the framework: Observable, ObservableValue, WritableValue, ReadOnlyProperty, Property, and Binding. We show you the capabilities offered by these fundamental interfaces of the framework. We then show you how Property objects are bound together, how Binding objects are built out of properties and other bindings—using the factory methods in the Bindings utility class, the fluent interface API, or going low-level by directly extending abstract classes that implement the Binding interface—and how they are used to easily propagate changes in one part of a program to other parts of the program without too much coding. We finish this topic by introducing the JavaFX Beans naming convention, an extension of the original JavaBeans naming convention that makes organizing your data into encapsulated components an orderly affair.
Because the JavaFX 2.0 properties and bindings framework is a nonvisual part of the JavaFX 2.0 platform, the example programs in this topic are also nonvisual in nature. We deal with Boolean, Integer, Long, Float, Double, String, and Object typed properties and bindings as these are the types in which the JavaFX 2.0 binding framework specializes. Your GUI building fun resumes in the next and further topics.
The need for exposing attributes of Java components directly to client code, allowing them to observe and to manipulate such attributes and to take action when their values change, is recognized early in Java’s life. The JavaBeans framework in Java 1.1 provided support for properties through the now familiar getter and setter convention. It also supported the propagations of property changes through its
PropertyChangeEvent and PropertyChangeListener mechanism. Although the JavaBeans framework is used in many Swing applications, its use is quite cumbersome and requires quite a bit of boilerplate code. Several higher-level data binding frameworks were created over the years with various levels of success. The heritage of the JavaBeans in the JavaFX 2.0 properties and bindings framework lies mainly in the JavaFX Beans getter, setter, and property getter naming convention when defining JavaFX 2.0 components. We talk about the JavaFX Beans getter, setter, and property getter naming convention later in this topic, after we have covered the key concepts and interfaces of the JavaFX 2.0 properties and bindings framework.
Another strand of heritage of the JavaFX 2.0 properties and bindings framework comes from the JavaFX Script language that was part of the JavaFX 1.x platform. Although the JavaFX Script language was deprecated in the JavaFX 2.0 platform in favor of a Java-based API, one of the goals of the transition was to preserve most of the powers of the JavaFX Script’s bind keyword, whose expressive power has delighted many JavaFX enthusiasts. As an example, JavaFX Script supports the binding to complex expressions:
This code will automatically recalculate the value of c whenever the values of a, b, or m are changed. Although the JavaFX 2.0 properties and bindings framework does not support all of the binding constructs of JavaFX Script, it supports the binding of many useful expressions. We talk more about constructing compound binding expressions after we cover the key concepts and interfaces of the framework.
