As I understand it, when using FXML to describe a Java FX scene, the controller class is written manually and it's member variables and methods can then be referenced from the .fxml file. When loading the scene using the FXMLLoader, member variables are set to the corresponding scene elements and methods are wired up to the corresponding events automatically. This works but is very cumbersome as changes need to be done in two places and any mistakes will only show up at runtime.
I've seen other GUI frameworks that allow you to instead generate the controller from a scene description as an abstract class which needs to be implemented to access the scene elements and handle the events. An example of what I mean:
I would create the following .fxml file (e.g. using the JavaFX Scene Builder):
<AnchorPane ... >
<children>
<Button fx:id="button" ... text="Button" onAction="#buttonPressed" />
</children>
</AnchorPane>
Somewhere in my build process, the following .java file would be created (e.g. using a Maven plugin):
abstract class TestController {
protected final Parent root;
protected final Button button;
{
// Load test.fxml file
// Assign scene elements to root and button
// Attach event handler to the button that calls buttonClicked()
}
protected abstract void buttonClicked(ActionEvent event);
}
I could then, possibly multiple times, create a concrete implementation of that controller:
final class TestControllerImpl extends TestController {
TestControllerImpl(String buttonLabel) {
button.setText(buttonLabel);
}
@Override
protected void buttonClicked(ActionEvent event) {
button.setText("I've been clicked! What a great day!");
}
}
Is there a project with the goal to do this? Or is there a problem with this approach applied to FXML?
I see the following benefits from this approach:
- Declarations for member variables and methods for the controller are automatically generated.
- All member variables are final and protected instead of non-final and either public or annotated.
- The same for methods, they are protected instead of either public or annotated.
- Not implementing a method or misspelling it's name will lead to a compiler error.
- Programmatic setup of the scene can be done in the constructor instead of an
initialize()method because the constructor will run after the scene has been loaded and its elements assigned to the member variables.
