JavaFX to JavaScript and Back Part 1


One of the most impressive features that I’ve seen relating to JavaFX, is the ability of an Applet to interact with the browser via JavaScript and HTML. The browser can also interact back with JavaFX code. There are plenty of examples out there but I’d like to add one more to the pile of cool examples. It may be cool using AJAX concepts with JavaScript & HTML, but using the concept with JavaFX is just amazing. The possibilities are endless. “JavaFX to JavaScript and Back Part 1” will demonstrate what the application will do and “JavaFX to JavaScript and Back Part 2” will be on steps on how-to do it.

While I was a kid growing up, I would go to the bowling alley to get a 25 cent(US) bouncy ball from the vending machine. I’ve lost many a bouncy ball in the parking lot from bouncing them as hard as I could. In this example I will create a 500 by 400 pixel sized bouncy ball containment field in JavaFX. This is to prevent them from ever leaving me like they did when I was a kid. :-(

Note: Thanks to Stephen Chin an author of the book Pro JavaFX Platform and WidgetFX for allowing me to host The Bouncy Ball Containment Field Click Here to run!

(Tip: If in Firefox just middle mouse click link to launch in another tab)

Initial Ball added to ball world

Here is an example of an HTML page with an embedded JavaFX applet with HTML form elements below for data input to create bouncy balls. The demo allows a user to specify the number of balls to add to the scene called the “Add balls to Scene” field.  When the “Add Ball(s)” button is pressed the JavaScript code will pass the number of balls to the JavaFX public script level function called addBalls() which will create bouncy balls. When balls are added the JavaFX Script code will talk back to the HTML read-only field called “Number of balls” to show the current number of balls in the containment field (Scene). On the JavaFX side of things the location, velocity, size and color of the balls will be generated randomly and rendered on the scene.  You should notice the new JavaFX 1.2 Toggle Button component on the upper left. It is used to stop and  start the animation of the bouncing of the balls (Timeline pause & play to be exact). The first use case scenario is add balls which depicts the JavaScript to JavaFX data flow. The second use case scenario is display the current number of bouncy balls in the containment field which depicts the JavaFX to JavaScript data flow.

Balls addBalls(lots of balls)

This shows when the user specifies a whole bunch of balls to add.

Button to use JavaScript function addBalls()
Button to use JavaScript function addBalls()

A ball can be removed from the scene by just clicking an individual ball.  The field “Number of balls” input field is really a read-only field that is updated from the JavaFX side whenever balls are added and removed from the bouncy ball containment field.

More Bouncy Balls

By adding many balls I wanted to see how well it would perform.

Tons of Bouncy Balls

Here I add balls, lots of balls! The bouncy ball containment field now holds 400 bouncy balls. Although I might not be doing things efficiently I noticed my CPU was performing adequately. The utilization was between 41% to 46% (older Dell hyper-threading Inspiron XPS laptop Pentium(R) 4 CPU 3.40 GHz) using Windows XP SP 3. It was a smooth animation with no flicker. The Ball class is a Custom Node which contains a Circle with an effect called Radial Gradient to give it a 3D sphere look.

Dragging JavaFX Applet out of Web Page

By using the Alt key along with mouse drag the JavaFX applet will appear to be pulled out of the browser’s Web page and out onto the desktop.

JavaFX Applet living outside of browser

By default, when you drag the applet out of the browser onto your desktop a small “close button” appears on the upper right corner of your application. When the user clicks the “close button” box the JavaFX applet will snap right back into the browser. Another thing to note is that when the JavaFX applet is running outside the browser and the user subsequently closes the browser the applet will remain running independent of the browser.   This introduces an interesting ability that adds a new dimension to usability on the desktop.  As the user becomes drawn into the application experience the need to be attached to the Web page will be obsolete. Another cool effect that I have added to the Application is transparency or opacity level when the mouse cursor is exiting or entering the scene area. When the user moves the mouse away from the application the screen will fade to a subtle transparency. When the user moves the mouse cursor into the application screen area the background becomes fully opaque (white in this case).

Fully Opaque when mouse moves into application
Fully Opaque when mouse moves into application

This fading effect helps the user transition from one application to another.

The last, item of the desktop experience to mention is the Java JNLP mechanism that asks the user if he or she wants to create a short-cut icon for the application to launch at a later time.

Create short-cut dialog
Create short-cut dialog

To reproduce the dialog asking for a shortcut, you would drag the applet out of browser, then close tab or browser application and then a dialog will appear asking to create the short-cut.


Building the bouncy ball containment field was extremely fun. I learned a lot about boundsInParent which taught me that it is the rectangular region after all transformations to the node has been applied when adding balls to the Scene. As the future of the Web 2.0 apps grow users will demand richer interfaces and better content. I believe JavaFX has made great strides in desktop development and also increasing the usability factor of desktop applications by leaps and bounds. In Part 2 of “JavaFX to JavaScript and Back” I will detail a step-by-step tutorial on how to build the JavaFX applet you see here. Let me know what you think. Feedback is always welcome!

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