JavaFx handler override

Question

I have a fxml file build from fxml builder and I am using it by a loader in Java.

URL resource = getClass().getClassLoader().getResource("fxmlFile.fxml"); FXMLLoader loader = new FXMLLoader(resource, resourceBundle); Pane rootPane = (Pane) loader.load();

this fxml file maps click event to my class;

<Group id="Group" layoutX="0.0" layoutY="0.0" onMouseReleased="#handleThis" scaleX="1.0" scaleY="1.0"> ... <Group/>

so I implement my handler in my class, lets call it MyClass;

public class MyClass { public void createScene() throws IOException { URL resource = getClass().getClassLoader().getResource("fxmlFile.fxml"); FXMLLoader loader = new FXMLLoader(resource, resourceBundle); Pane rootPane = (Pane) loader.load(); ... } @FXML public void handleThis(ActionEvent event) { System.out.println("from MyClass"); } ... }

Now I extend MyClass as MyExtendedClass and override handleThis method;

public class MyExtendedClass extends MyClass { @Override public void handleThis(ActionEvent event) { System.out.println("from MyExtendedClass"); } }

My question is, I cannot manage to work handle method in my extended class. It does not overrides it. How can I achieve to make it print "from MyExtendedClass" instead of "from MyClass"?

have you tried onMouseRelease="#MyExtendedClass.handleThis" ? — hanbin615
– hanbin615, Commented May 13, 2015 at 11:24
Then how would the FXMLLoader even know about the subclass? — James_D
– James_D, Commented May 13, 2015 at 12:17

Prometheus · Accepted Answer · 2015-05-13 14:55:46Z

When createScene() is called on an instance of MyExtendedClass, the FXMLLoader parses the FXML file, reads the fx:controller="MyClass" attribute and instantiates a new object of type MyClass. That is why the base method is always called. The FXMLLoader doesn't know about MyExtendedClass.

There is a - hackish - way to achieve what you want (i.e. doing the loading in MyClass and still defining the controller in FXML):

public class MyClass { public void createScene() { try { FXMLLoader loader = new FXMLLoader(); loader.setLocation(getClass().getResource("FXML.fxml")); // set a controller factory that returns this instance as controller // (works in this case, but not recommended) loader.setControllerFactory(controllerType -> this); pane = (Pane) loader.load(); } catch (IOException e) { throw new RuntimeException(e); } } }

It would be cleaner to instantiate the controller and pass it to the FXMLLoader.
For this the fx:controller="" attribute must be removed from the FXML file.

public class Main extends Application { @Override public void start(Stage primaryStage) throws Exception { MyClass controller = new MyExtendedClass(); FXMLLoader loader = new FXMLLoader(); loader.setLocation(getClass().getResource("FXML.fxml")); loader.setController(controller); Pane pane = (Pane) loader.load(); primaryStage.setScene(new Scene(pane)); primaryStage.show(); } public static void main(String[] args) { launch(args); } }

Or use fx:controller="MyClass" to define the base type in the FXML file and let a controller factory decide the actual implementation.

public class Main extends Application { @Override public void start(Stage primaryStage) throws Exception { FXMLLoader loader = new FXMLLoader(); loader.setLocation(getClass().getResource("FXML.fxml")); loader.setControllerFactory(controllerType -> { if (MyClass.class.equals(controllerType)) return new MyExtendedClass(); else return null; // return some other controller }); Pane pane = (Pane) loader.load(); MyClass controller = (MyClass) loader.getController(); primaryStage.setScene(new Scene(pane)); primaryStage.show(); } public static void main(String[] args) { launch(args); } }

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