Java/JavaFX事件处理程序和setFill()问题

import javafx.application.Application;
import javafx.event.ActionEvent;
import javafx.event.EventHandler;
import javafx.scene.Scene;
import javafx.scene.control.Button;
import javafx.scene.layout.StackPane;
import javafx.stage.Stage;

public class EventHandlingExample extends Application {

    @Override
    public void start(Stage primaryStage) {
        Button button = new Button("Click me!");
        button.setOnAction(new EventHandler<ActionEvent>() {
            @Override
            public void handle(ActionEvent event) {
                System.out.println("Button clicked!");
            }
        });

        StackPane root = new StackPane();
        root.getChildren().add(button);

        Scene scene = new Scene(root, 300, 200);

        primaryStage.setTitle("Event Handling Example");
        primaryStage.setScene(scene);
        primaryStage.show();
    }

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

import javafx.application.Application;
import javafx.scene.Scene;
import javafx.scene.layout.StackPane;
import javafx.scene.paint.Color;
import javafx.scene.shape.Circle;
import javafx.stage.Stage;

public class FillExample extends Application {

    @Override
    public void start(Stage primaryStage) {
        Circle circle = new Circle(50);
        circle.setFill(Color.RED);

        StackPane root = new StackPane();
        root.getChildren().add(circle);

        Scene scene = new Scene(root, 200, 200);

        primaryStage.setTitle("Fill Example");
        primaryStage.setScene(scene);
        primaryStage.show();
    }

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