CODEWITHSUNDEEP
javajavafxlistener
Gianpaolo
Gianpaolo

Reputation: 95

JavaFX addListener not working

I'm quite a newbie on JavaFX and I need to bind the visible property of a Label in a way that, if the value it represents reaches 0, the Label should be invisible. Also, it needs to be updated when the bounded integerProperty value changes.

This is my code:

@FXML
private Label kingRewardLabel;

// many other stuff between

IntegerProperty kingBonus = mainApp.getLocalModel().getMap().kingBonus();

kingBonus.addListener((observable, oldValue, newValue) -> {
    if (newValue.equals(0)) {
        kingRewardLabel.setVisible(false);
    } else {
        kingRewardLabel.setText(String.valueOf(newValue.intValue()));
    }
});

// testing the listener 
kingBonus.setValue(25);

I have already tried to debug a little but everything seems fine, no error, no exception thrown, just the listener does not work, or at least not as I expect, because the Label still show the default text "Label", instead of "25"

Upvotes: 2

Views: 3960

Answers (2)

DVarga
DVarga

Reputation: 21799

You can use simply bindings to achieve this:

kingRewardLabel.textProperty().bind(kingBonus.asString());
kingRewardLabel.visibleProperty().bind(kingBonus.greaterThan(0));

The Label kingRewardLabel will display the value of the IntegerProperty kingBonus and it is only visible if the displayed value is greater than zero.

But, if you want to stay with listeners:

kingBonus.addListener((obs, oldVal, newVal) -> {
    kingRewardLabel.setVisible(newVal.intValue() > 0);
    kingRewardLabel.setText(newVal.toString());
});

This is almost the same as your listener in the question, but in that case, if the Label became invisible, it will never become visible again as kingRewardLabel.setVisible(true) is never called.

Finally, to answer your question about why the listener is "not working" - there can be two possible reasons:

1) The Label, which one is displayed is not the Label stored in kingRewardLabel

2) At the time when you call kingBonus.setValue(25);, the value stored in kingBonus is already 25, no changed event will be fired, therefore the listener is not executed at all.

Upvotes: 8

GOXR3PLUS
GOXR3PLUS

Reputation: 7255

You can go like this:

 kingBonus.addListener(l -> {
            int value = kingBonus.getValue().intValue();
            System.out.println("Entered listener for value:" + value);
            if (value == 0)
                kingRewardLabel.setVisible(false);
            else
                kingRewardLabel.setText(value+"");  
        });
    });

Upvotes: 0

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