Java Magazine - May/June 2012

//fix this /

COMMUNITY

In the last issue, Jonathan Giles showed us Java code that demonstrates a thread retrieving from a remote datasource, and updates a JavaFX ProgressBar control. He asked if this code was guaranteed to work in all environments.

The correct answer is #3: No. The ProgressBar must always be updated from the JavaFX application thread. Whenever you use separate threads in JavaFX, you must always be sure to update the scene only via the JavaFX application thread. This is achieved by calling Platform.runLater(..) from within your threading code. If this is not done, the user interface may not appear as expected in all circumstances (and on all machines). Future JavaFX releases may even make this a runtime exception, so do the right thing now!

2 THE CODE Consider the following code fragment for a JavaFX application:

...
IntegerProperty myInt = new SimpleIntegerProperty(5);
IntegerProperty myBoundInt = new SimpleIntegerProperty(0);
myBoundInt.bind(myInt);
myInt.set(8);
System.out.println("My bound integer's value is: "+ myBoundInt);
myBoundInt.set(5);
System.out.println("My bound integer's value is: "+ myBoundInt);

JAVA IN ACTION

3 WHAT S THE FIX?

What will be the output when you try to run this code?

1) My bound integer's value is: 8 My bound integer's value is: 5

This issues challenge comes from Angela Caicedo, a Java evangelist at Oracle.

2) My bound integer's value is: 5 My bound integer's value is: 5

ABOUT US

1 THE PROBLEM One of the coolest features of JavaFX is binding capabilities. When JavaFX properties participate in bindings, changes made to one object are automatically reflected in another object. This is particularly useful when creating graphical user interfaces because you can automatically keep the display synchronized with the underlying data.