How to listen resize event of Stage in JavaFX?

Question

I want to perform some functionality on resize event of form (or Scene or Stage whatever it is).

But how can I detect resize event of form in JavaFX?

Answer 1

You can listen to the changes of the widthProperty and the heightProperty of the Stage :

stage.widthProperty().addListener((obs, oldVal, newVal) -> {
     // Do whatever you want
});

stage.heightProperty().addListener((obs, oldVal, newVal) -> {
     // Do whatever you want
});

---

Note: To listen to both width and height changes, the same listener can be used really simply:

ChangeListener<Number> stageSizeListener = (observable, oldValue, newValue) ->
    System.out.println("Height: " + stage.getHeight() + " Width: " + stage.getWidth());

stage.widthProperty().addListener(stageSizeListener);
stage.heightProperty().addListener(stageSizeListener); 

Answer 2

Keeping a fixed width to height ratio:

stage.minHeightProperty().bind(stage.widthProperty().multiply(0.5));
stage.maxHeightProperty().bind(stage.widthProperty().multiply(0.5));

Answer 3

Cut the long story short :

container.widthProperty().addListener(new ChangeListener<Number>() {
        @Override
        public void changed(ObservableValue<? extends Number> observable, Number oldValue, Number newValue) {
            if (newValue.floatValue()!=oldValue.floatValue()) resizeKids(newValue);
        }
    });

Also you may want to check new width/height with the old values for prevent duplication .