Create User Interfaces - JavaFX: Developing Rich Internet Applications - page 148

public var text:String = getJTextArea().getText() on replace {
getJTextArea().setText(text);
};
Next, to update the JavaFX text variable, when the JTextArea text attribute
changes, we need to install a JavaBeans property change listener on the JTextArea .
init {
var textArea = getJTextArea();
textArea.addPropertyChangeListener(
PropertyChangeListener {
public override function propertyChange(
ev: PropertyChangeEvent) : Void {
var property = ev.getPropertyName();
if(property == "text") {
text = textArea.getText();
}
...
Now, whenever the JTextArea text changes, a JavaBeans property change
event will be fired, and the JavaFX corresponding instance variable can be set.
However, we have a problem. If the JavaFX program changes the JavaFX text
instance variable, it will in turn call the JTextArea.setText() method, which
causes the JavaBeans property change event to fire, which in turn sets the JavaFX
text instance variable. We are stuck in an infinite circle and eventually our pro-
gram will crash.
To overcome this, we need to add a flag indicating this condition to our JavaFX
class. This indicates that the JavaFX text variable change caused the property
change event to fire, so there is no need for the JavaBeans property change lis-
tener to update the companion JavaFX variable. We added the private Boolean
variable, inChange .
var inChange = false;
public var text:String = getJTextArea().getText()
on replace {
if(not text.equals(getJTextArea().getText())){
try {
inChange = true;
getJTextArea().setText(text);
}finally {
inChange = false;
}
}
};
...