Drop-shadow in an undecorated Pane

I'm trying to make my Pane a little bit better, visually, so, what I'm doing is: set my stage UNDECORATED (OK) and (TRYING) to add a drop-shadow effect (NOT OK).

I've found some similar cases, though none work: creating undecorated stage in javafx 2.0 and How to add shadow to window in JavaFX?.

It seems like the drop-shadow just isn't set. I can't understand why.

This is what I have:

public static int showConfirmDialog(Window father, String title, String body, String[]      msgBtn) 
{
    System.out.println("La vai eu");
    AnchorPane ap = createPaneWithButton(2, msgBtn,body);
    
    ap.setEffect(initDropShadow());
    Scene scene = new Scene(ap);
    
    Stage stage = new Stage();
    
    stage.setTitle(title);
    
    scene.setFill(null);
    stage.initStyle(StageStyle.TRANSPARENT);
    
    
    stage.setScene(scene);
    stage.initStyle(StageStyle.UNDECORATED);
    stage.show();
    
    return 1;
}

private static AnchorPane createPaneWithButton(int qtBtn, String[] msgsBtn, String body) {
    AnchorPane ap = createPane();
    HBox laneBtn = new HBox(30);
    VBox vbox = new VBox(20);
    
    BorderPane layout = new BorderPane();
    
    Button btn;
    
    for(int i = 0; i < qtBtn; i++ ){
        btn = new Button();
        btn.setText(msgsBtn[i]);
        
        laneBtn.getChildren().add(btn);
    }
    
    vbox.getChildren().add(new Text(body));
    vbox.getChildren().add(laneBtn);
    
    layout.setCenter(vbox);
    
    ap.getChildren().add(layout);
    
    return ap;
}

private static AnchorPane createPane() {
    AnchorPane ap = new AnchorPane();
    
    ap.setLayoutX(250);
    ap.setLayoutY(50);
    
    return ap;
}