Java Magazine - November/December 2011

Listing 1 is a simple example of using this class. Let’s work through the details, because some things aren't obvious.

In line 8, we instantiate a JFXPanel object, but initially we tell it nothing about what it will contain. That information will be provided later. This component can be added to a Swing Container just as any other Swing component.

To understand how we encapsulate the JavaFX scene, we need some details about threads in Swing and JavaFX. Swing uses a single event dispatch thread (EDT), and JavaFX uses an application thread. Both effectively do the same thing, which is to process asynchronous events that affect the UI (for example, button presses, updates to displayed values, window resizing, and so on).

As a Swing component, the JFXPanel object must be accessed only from the Swing EDT. The only exception to this is the setScene() method, which must be accessed from the JavaFX application thread.

In order to set the scene for the JFXPanel object, we must create another object that implements the Runnable interface, which can then be posted to the event queue and executed at some ( unspecified) time in the future. We use the static utility method, runLater(), provided in the Platform utility class, and then an anonymous inner class to instantiate the Runnable object. Due to the inner class restrictions, the reference to the JFXPanel must be made final.

The initFXComponent() method is
where the real JavaFX work happens.
Because JavaFX uses a scene graph, we
need to create a Scene object to hold the
parent node reference. When we instan-
tiate this object, we can also set the size
of the scene in pixels, which will then
be used by the Swing layout manager to
position the JavaFX component. We also
set the root node of the scene to be the
graph of objects that will be displayed.

1 public void init() {

2 setSize(300, 200);

3 setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); 4 setLayout(new BorderLayout()); 5 6 /* Put the JavaFX scene in the middle */ 7 fxComponent = new SimpleFXComponent(this); 8 final JFXPanel fxPanel = new JFXPanel(); 9 add("Center", fxPanel); 10 11 /* Construct the JavaFX scene on its own application thread */ 12 Platform.runLater(new Runnable() { 13 @Override 14 public void run() { 15 Scene scene = new Scene(fxComponent, 200, 100); 16 scene.setFill(Color.BLUEVIOLET); 17 fxPanel.setScene(scene); 18 } 19 }); 20 21 /* Put the Swing button at the bottom */ 22 changeButton = new JButton("Change JavaFX Button"); 23 24... 25 26 add("South", changeButton); 27 setVisible(true); 28 }

COMMUNITY JAVA IN ACTION

Swing and JavaFX Events

There is one more basic part of Swing and JavaFX integration that needs to be addressed, which is how the components interact when a Swing component triggers a change in a JavaFX scene or vice versa. If the JavaFX scene wants to interact with Swing components, the code must be wrapped in a Runnable object and placed on the EDT using the SwingUtilities.invokeLater() method, as shown in Listing 2.

For the opposite case, where a Swing component needs to interact with a JavaFX scene, the code must again be wrapped in a Runnable object, but this time it must be placed on the JavaFX application thread using the Platform .runLater() method, as shown in Listing 3.

ABOUT US

See all listings as text

only a few more lines of code than using a normal Swing component. Having the JavaFX scene and Swing components interact is also straightforward. You just have to remember to wrap the necessary code in a Runnable object and place it on the correct queue for execution.

In the next article, we’ll take this
knowledge and start to modify our Swing
application to add exciting new
components that are created using
JavaFX. </article>