JavaFX Controller loading

Question

I came across some very strange behaviour a couple of times every time forgetting the trick.

FXMLLoader loader = new FXMLLoader();
loader.setLocation(getClass().getResource("view/window.fxml"));
Parent root = loader.load();
GuiController controller = loader.getController();

Now the controller is not null.

However, after I do this...

FXMLLoader loader = new FXMLLoader();
loader.setLocation(getClass().getResource("view/window.fxml"));
Parent root = loader.load(getClass().getResource("view/window.fxml"));
GuiController controller = loader.getController();

The controller is now null.

I understand that the loader somehow looses his grip on location? I would very much appreciate somebody telling me that this is an expected behaviour and explain me why.

Please note that is looked quite a bit after post concerning this problem found nothing, and discovered the solution only after 2h of experimentation, so please don't link me up with similar looking questions.

You presumably mean loader, not fxmlLoader in both calls to setLocation(...). — James_D
– James_D, Commented Nov 12, 2015 at 22:21

James_D · Accepted Answer · 2015-11-12 22:19:20Z

1

The FXMLLoader method load(URL) is a static method. So your second code block is equivalent to (compiles to)

FXMLLoader loader = new FXMLLoader();
// I assume you mean loader, not fxmlLoader, in the next line:
loader.setLocation(getClass().getResource("view/window.fxml"));
Parent root = FXMLLoader.load(getClass().getResource("view/window.fxml"));
GuiController controller = loader.getController();

In other words, you never invoke load(...) on loader: hence loader never parses the FXML and never instantiates the controller.

In your first code block, you invoke the no-arg load() method, which is an instance method.

answered Nov 12, 2015 at 22:19

James_D

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3 Comments

ZbyszekKr Over a year ago

Haven't noticed the static keyword in the documentation. Thank you very much. :) Lost quite a lot of my evening for that.

ZbyszekKr Over a year ago

For some reason I had my warning suppressed for this class... After switching them back on it performed as you said it would. Thanks.

James_D Over a year ago

Most IDEs will give you a warning if you call a static method from a reference.

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