如果所有者窗口不可见，则不显示JavaFX弹出窗口

import javafx.application.Application;
import javafx.scene.Scene;
import javafx.scene.control.Button;
import javafx.scene.layout.VBox;
import javafx.stage.Stage;

public class PopupWindowExample extends Application {

    @Override
    public void start(Stage primaryStage) {
        primaryStage.setTitle("Main Window");

        Button showPopupButton = new Button("Show Popup");
        showPopupButton.setOnAction(e -> {
            Stage popupStage = new Stage();
            popupStage.setTitle("Popup Window");
            popupStage.initOwner(primaryStage); // 设置所有者窗口为主窗口

            VBox popupLayout = new VBox();
            popupLayout.getChildren().add(new Button("Close Popup"));

            Scene popupScene = new Scene(popupLayout, 200, 200);
            popupStage.setScene(popupScene);
            popupStage.show();
        });

        VBox mainLayout = new VBox();
        mainLayout.getChildren().add(showPopupButton);

        Scene mainScene = new Scene(mainLayout, 400, 400);
        primaryStage.setScene(mainScene);
        primaryStage.show();
    }

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