Why does the JavaBean adapter not update the JavaFX property? - javafx

Question

I'm new to JavaFX and need a bidirectional binding between a GUI (using JavaFX properties) and my old Java code (not using JavaFX properties). I tried using a JavaBean adapter as the following simple example shows:
import java.beans.PropertyChangeListener;
import java.beans.PropertyChangeSupport;
import javafx.beans.property.DoubleProperty;
import javafx.beans.property.SimpleDoubleProperty;
import javafx.beans.property.adapter.JavaBeanDoubleProperty;
import javafx.beans.property.adapter.JavaBeanDoublePropertyBuilder;
public class App
{
public static void main(String[] args) throws NoSuchMethodException
{
Pojo pojo = new Pojo();
FXModel model = new FXModel();
JavaBeanDoubleProperty adapter = JavaBeanDoublePropertyBuilder
.create().bean(pojo).name("value").build();
model.valueProperty().bindBidirectional(adapter);
System.out.println("Adapter before: " + adapter.get());
System.out.println("Model before: " + model.getValue());
System.out.println("Bean before: " + pojo.getValue());
pojo.setValue(123d);
System.out.println();
System.out.println("Adapter after: " + adapter.get());
System.out.println("Model after: " + model.getValue());
System.out.println("Bean after: " + pojo.getValue());
}
public static class Pojo
{
private double value;
public double getValue()
{
return value;
}
public void setValue(double value)
{
this.value = value;
}
}
public static class FXModel
{
private final DoubleProperty value = new SimpleDoubleProperty();
public double getValue()
{
return value.get();
}
public void setValue(double value)
{
this.value.set(value);
}
public DoubleProperty valueProperty()
{
return value;
}
}
}
The generated output is
Adapter before: 0.0 Model before: 0.0 Bean before: 0.0
Adapter after: 123.0 Model after: 0.0 Bean after: 123.0
So, by setting the "normal" Java object to a new value the JavaBeanDoubleProperty is informed about the change, but the JavaFX property is not, although it is bound to the adapter. Why?
Even by adding a PropertyChangeSupport to Pojo as described here,
public static class Pojo
{
private double value;
private PropertyChangeSupport pcs;
public Pojo()
{
pcs = new PropertyChangeSupport(this);
}
public double getValue()
{
return value;
}
public void setValue(double value)
{
final double oldValue = this.value;
this.value = value;
pcs.firePropertyChange("name", oldValue, value);
}
public void addPropertyChangeListener(
final PropertyChangeListener listener)
{
pcs.addPropertyChangeListener(listener);
}
},
it does not work. (Unfortunately, a second trial using BeanPathAdapter also did not work.)

Answer 1

You just made a slip in Pojo.setValue(double value). This method fires a PropertyChangeEvent for the property "name". It supposed to be "value".
Just change it to
public void setValue(double value)
{
final double oldValue = this.value;
this.value = value;
pcs.firePropertyChange("value", oldValue, value);
}
and it will work.

Answer 2

The binding is supposed to be between the adapter and model. Do not modify the pojo values directly, the adapter will do the updating. Replacing the line:
pojo.setValue(123d);
with this,
adapter.setValue(123d);
results in the expected output with all values updated including the pojo. The same happens when you set the value of the model. The diagrams at this post may help you visualise the working.