dropshadow用于透明警报不起作用的JavaFx

import javafx.application.Application;
import javafx.scene.Group;
import javafx.scene.Scene;
import javafx.scene.control.Alert;
import javafx.scene.control.Alert.AlertType;
import javafx.scene.effect.DropShadow;
import javafx.scene.paint.Color;
import javafx.scene.shape.Rectangle;
import javafx.stage.Stage;

public class DropShadowExample extends Application {

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

    @Override
    public void start(Stage stage) {
        Group root = new Group();

        Rectangle rectangle = new Rectangle(100, 100, Color.RED);
        rectangle.setTranslateX(100);
        rectangle.setTranslateY(100);

        DropShadow dropShadow = new DropShadow();
        dropShadow.setRadius(10);
        dropShadow.setOffsetX(5);
        dropShadow.setOffsetY(5);
        dropShadow.setColor(Color.GRAY);

        rectangle.setEffect(dropShadow);

        root.getChildren().add(rectangle);

        Scene scene = new Scene(root, 300, 300);
        stage.setScene(scene);
        stage.show();
    }
}