JavaFX: How to get stage from controller during initialization

initializationjavafxjavafx-2javafx-8stage

I want to handle stage events (i.e. hiding) from my controller class. So all I have to do is to add a listener via

((Stage)myPane.getScene().getWindow()).setOn*whatIwant*(...);

but the problem is that initialization starts right after

Parent root = FXMLLoader.load(getClass().getResource("MyGui.fxml"));

and before

Scene scene = new Scene(root);
stage.setScene(scene);

thus .getScene() returns null.

The only workaround I found by myself is to add a listener to myPane.sceneProperty(), and when it becomes not null I get scene, add to it's .windowProperty() my !goddamn! listener handling which I finally retrieve stage. And it all ends with setting desired listeners to stage events.
I think there are too many listeners.
Is it the only way to solve my problem?

Best Answer

You can get the instance of the controller from the FXMLLoader after initialization via getController(), but you need to instantiate an FXMLLoader instead of using the static methods then.

I'd pass the stage after calling load() directly to the controller afterwards:

FXMLLoader loader = new FXMLLoader(getClass().getResource("MyGui.fxml"));
Parent root = (Parent)loader.load();
MyController controller = (MyController)loader.getController();
controller.setStageAndSetupListeners(stage); // or what you want to do

Related Solutions

JavaFX 2.0: Closing a stage (window)

The documentation you linked states that stage.close():

Closes this Stage. This call is equivalent to hide().

As hide() is equivalent to close() and close() closes the stage, then hide() also closes the stage.

When all stages in an application are hidden (or closed if you like, because it is the same thing), the application exits. Confusing, I know, but that's just the way the JavaFX team decided to name and implement the actions.

If desired, the Platform.setImplicitExit(boolean) method can be used to switch off the default behaviour of exiting the application when the last window is closed or hidden.

Then it comes to the question, How can we hide the stage without closing it completely?

I don't think hide() or the equivalent close() method will close the stage "completely" as in freeing up all resources related to the window (as long as you keep a reference to the stage around somewhere). I think it just makes it so that the stage is not visible. You could probably call show() after calling close() and the window would likely be made visible again (I didn't try it). Though, if you were to do that, then it would be more intuitive to call hide() rather than close().

My guess is that if you no longer keep any references to a stage in your application and the stage is closed or hidden, then perhaps the JVM will release all resources related to the stage whenever its algorithm decides to garbage collect those resources (again I didn't test this and it may not work that way).

Moving an undecorated stage in javafx 2

I created a sample of an animated clock in an undecorated window which you can drag around.

Relevant code from the sample is:

// allow the clock background to be used to drag the clock around.
final Delta dragDelta = new Delta();
layout.setOnMousePressed(new EventHandler<MouseEvent>() {
  @Override public void handle(MouseEvent mouseEvent) {
    // record a delta distance for the drag and drop operation.
    dragDelta.x = stage.getX() - mouseEvent.getScreenX();
    dragDelta.y = stage.getY() - mouseEvent.getScreenY();
  }
});
layout.setOnMouseDragged(new EventHandler<MouseEvent>() {
  @Override public void handle(MouseEvent mouseEvent) {
    stage.setX(mouseEvent.getScreenX() + dragDelta.x);
    stage.setY(mouseEvent.getScreenY() + dragDelta.y);
  }
});

...

// records relative x and y co-ordinates.
class Delta { double x, y; }

Code looks pretty similar to yours, so not quite sure why your code is not working for you.

Best Answer

Related Solutions

JavaFX 2.0: Closing a stage (window)

Moving an undecorated stage in javafx 2

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