Java™ How To Program (Early Objects), Tenth Edition

Property Listeners

To perform an arbitrary task when a propery’s value changes, you can register a property listener. Lines 41–64 register the property listeners for the Sliders’ value properties. Consider lines 41–46:

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redSlider.valueProperty().addListener(    (observableValue, oldValue, newValue) ->    {       red = newValue.intValue();       colorRectangle.setFill(Color.rgb(red, green, blue, alpha));    });

First, we call the redSlider’s valueProperty method to get the property’s DoubleProperty object (which is an ObservableValue) has an addListener method that registers an object of the functional interface ChangeListener to respond when a property change occurs. The ChangeListener’s changed method has three ...