Bidirectional binding between DoubleProperty and ObjectProperty Double

Question

Is there a way to bind a DoubleProperty and an ObjectProperty<Double> in a bidirectional manner?
For a unidirectional solution, one could utilize low-level binding api, but I couldn't find a way to achieve the same for bidirectional binding.

Answer 1

DoubleProperty implements Property<Number>, so you can bind bidirectionally between DoubleProperty and ObjectProperty<Number>, but not (directly) between DoubleProperty and ObjectProperty<Double>, as far as I can see.
One way is just to use listeners:
final DoubleProperty dProp = new SimpleDoubleProperty();
  final ObjectProperty<Double> propD = new SimpleObjectProperty<>();
  propD.addListener(new ChangeListener<Number>() {
      @Override
      public void changed(ObservableValue<? extends Number> observable,
          Number oldValue, Number newValue) {
        if (dProp.getValue() != newValue) {
          dProp.setValue(newValue);
  dProp.addListener(new ChangeListener<Number>() {
      @Override
      public void changed(ObservableValue<? extends Number> observable,
          Number oldValue, Number newValue) {
        if (propD.get() != newValue) {
          propD.set((Double) newValue);
And another way, which is less code but a bit obtuse and less efficient, is to use an intermediate StringProperty and bind with the appropriate StringConverters:
final StringProperty sProp = new SimpleStringProperty();
  Bindings.bindBidirectional(sProp, dProp, new NumberStringConverter());
  Bindings.bindBidirectional(sProp, propD, new DoubleStringConverter());
I don't see another way: if you can arrange for your ObjectProperty<Double> to be an ObjectProperty<Number>, that would obviously be best. I don't see a more general way to bind bidirectionally between Property<T> and Property<S> when one of S, T is not a String.