JavaFX：使用注释创建的构造函数

Question

I am creating a JavaFX application and when I create a controller for my FXML file the constructors are always the same.

Is there any way to write a custom annotation to create my constructors? Something like this:

public class MyClass() {

    @InitFxml(file = "test")
    public MyClass() {
    }

And the @InitFxml would inject the following code into the constructor:

FXMLLoader loader = new FXMLLoader(getClass().getResource("test.fxml");
...

or is it possible to create annotation for the class which creates this default constructor?

Any help is greatly appreciated.

Answer 1

To process the annotation, you would have to define some kind of container that processed it, and always load your class through that container, or define an annotation processor which you attached to the compiler (I think: I know nothing about that second option).

Why not just pass a string as a parameter, though. You could define an interface:

import java.net.URL;

import javafx.fxml.FXMLLoader;


public interface CustomComponent {
    public default void loadFXML(String fxml) {
        try {
            URL resource = getClass().getResource(fxml);
            FXMLLoader loader = new FXMLLoader(resource);
            loader.setRoot(this);
            loader.setController(this);
            loader.load();
        } catch (Exception exc) {
            if (! (exc instanceof RuntimeException)) {
                throw new RuntimeException(exc);
            } else {
                throw (RuntimeException)exc ;
            }
        }
    }
}

and then just have your custom components implement it, calling the method from the constructor:

import javafx.application.Application;
import javafx.fxml.FXML;
import javafx.scene.Scene;
import javafx.scene.control.Label;
import javafx.scene.layout.VBox;
import javafx.stage.Stage;

public class CustomComponentTest extends Application {

    @Override
    public void start(Stage primaryStage) {
        Scene scene = new Scene(new CustomVBox(), 400, 400);
        primaryStage.setScene(scene);
        primaryStage.show();
    }

    public static class CustomVBox extends VBox implements CustomComponent {

        @FXML
        private Label label ;

        public CustomVBox() {
            loadFXML("CustomVBox.fxml");
        }

        @FXML
        private void click() {
            System.out.println("Click!");
        }
    }

    public static void main(String[] args) {
        launch(args);
    }
}

This seems to be no heavier than defining an annotation on an empty constructor.