How to bind two different JavaFx properties: String and Double (with StringConverter)?

Question

For this piece of code (JavaFX).

StringProperty sp;
DoubleProperty dp;

StringConverter<Double> converter = new DoubleStringConverter();    

Bindings.bindBidirectional(sp, dp, converter);

I get compilation error (in Eclipse IDE)

This is the method signature:

public static <T> void bindBidirectional(Property<String> stringProperty, Property<T> otherProperty, StringConverter<T> converter)

But if I remove parametrization (of StringConverter), then I get only warnings and code works.

StringConverter converter = new DoubleStringConverter();

I am trying to avoid to use raw type of generics so that I don't have to suppress warnings in my IDE.

So the question is:
What is the right pattern to write this piece of code?

Nikos Paraskevopoulos · Answer 1 · 2017-12-13T10:29:12.007

26

This is probably a small "trap" in JavaFX properties. If you look closely at the signature:

static <T> void bindBidirectional(Property<java.lang.String> stringProperty,
    Property<T> otherProperty, StringConverter<T> converter)

The parameter of the converter must match the parameter of the property. But (the surprize here) DoubleProperty implements Property<Number>, thus the mismatch in bindBidirectional. Luckily the solution is simple: use NumberStringConverter:

StringProperty sp = ...;
DoubleProperty dp = ...;
StringConverter<Number> converter = new NumberStringConverter();
Bindings.bindBidirectional(sp, dp, converter);

You get the extra benefit that you can specify the conversion format.

edited Dec 13 '17 at 10:29

answered Jan 30 '14 at 09:07

Nikos Paraskevopoulos

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17

Is there a way of doing this with unidirectional bindings? – ZbyszekKr Dec 01 '16 at 15:56
For unidirectional bindings see [this answer](https://stackoverflow.com/a/48588027/5178726) – Aron Hoogeveen Dec 01 '20 at 12:57

score 0 · Answer 2 · answered Oct 05 '20 at 11:40

That is the answer of my solution:

    ArrayList<Pair<Slider,Label>> sliderList = new ArrayList<Pair<Slider,Label>>(
            Arrays.asList(
                    new Pair<Slider,Label>(soundSlider, soundLabel),
                    new Pair<Slider,Label>(videoSlider, videoLabel),

    sliderList.forEach(p->{
        Bindings.bindBidirectional(p.getValue().textProperty(), p.getKey().valueProperty(), new NumberStringConverter() {
            @Override
            public String toString(Number value) {
                return super.toString(Math.round((double) value));
            }
        }); 
    });

How to bind two different JavaFx properties: String and Double (with StringConverter)?

2 Answers2