CODEWITHSUNDEEP
javafx
VANILKA
VANILKA

Reputation: 684

NullPointerException in binding

Hi I would like to bind a value depending other object. It this object is null the value will be set by default. But I still received NullPointerException. I expect that it will be catch by ".then(...) . but it is not the case 

    relationType.bind(Bindings.when(Bindings.createBooleanBinding(() -> ( relation == null || relation.get()== null), relation))
            .then(RelationType.NEUTRAL)
            .otherwise(relation
                    .get()
                    .typeProperty()));

All works fine when I add binding to Listener content : 

    relation.addListener((observable, oldValue, newValue) -> {

    if(newValue != null) {
        relationType.bind(Bindings
                .when(relation.isNull())
                .then(RelationType.NEUTRAL)
                .otherwise(newValue.typeProperty()));
    } else {
        relationType.unbind();
        relationType.setValue(RelationType.NEUTRAL);
    }

});

But I prefere to have only binding. That is possible ??

Upvotes: 1

Views: 687

Answers (1)

fabian
fabian

Reputation: 82461

The problem is the time when relation.get().typeProperty() gets evaluated. It's evaluated when the binding is created and not every time relation changes. You could work around this using a select binding, but you'll receive warnings in the console using this approach:

relationType.bind(Bindings.when(relation.isNull())
            .then(RelationType.NEUTRAL)
            .otherwise(Bindings.select(relation, "type"));

Upvotes: 2

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