import javafx.application.Application;
import static javafx.application.Application.launch;
import javafx.scene.control.Alert;
import javafx.scene.control.DialogEvent;
import javafx.stage.Stage;

/**
 *
 * @author lans
 */
public class DialogSizeFail extends Application {

    private volatile Alert alert;

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

    @Override
    public void start(Stage primaryStage) {
        alert = new Alert(Alert.AlertType.ERROR);
        alert.setOnShown(this::onShown);
        alert.setOnCloseRequest(this::onClosing);
        alert.show();
    }

    public void onClosing(DialogEvent event) {
        System.out.println("Dialog is closing.");
        System.out.println("Alert height: " + alert.getHeight() + ", DialogPane height: " + alert.getDialogPane().getHeight());
    }

    public void onShown(DialogEvent event) {
        System.out.println("Dialog is shown.");
        System.out.println("Alert height: " + alert.getHeight() + ", DialogPane height: " + alert.getDialogPane().getHeight());
    }
}