JavaFX - 加载下一个场景时保留工具栏

Question

加载新场景时如何保留工具栏？

到目前为止，这是我的代码：

Main.class

    public class Main extends Application {

    @Override
    public void start(Stage primaryStage) throws Exception{
        Parent root = FXMLLoader.load(getClass().getResource("Main.fxml"));
        primaryStage.setTitle("Test FXML application");
        primaryStage.setScene(new Scene(root, 400, 400));
        primaryStage.show();
    }

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

Main.fxml

<?import javafx.scene.layout.GridPane?>
<?import javafx.scene.control.Button?>
<?import javafx.scene.control.ToolBar?>
<GridPane fx:controller="main.java.Controller"
          xmlns:fx="http://javafx.com/fxml">
    <ToolBar prefHeight="40.0" prefWidth="400.0">
        <Button text="testButton" onAction="#testButton"/>
    </ToolBar>
</GridPane>

Controller.class

我认为这个问题就在这里。我如何生成下一个场景有点破碎。

public class Controller {
    @FXML
    private void testButton1() throws IOException {
        Parent window1;
        try {
            window1 = FXMLLoader.load(getClass().getResource("src/testButton1.fxml"));
            Stage window1Stage;
            Scene window1Scene = new Scene(window1, 400, 400);
            window1Stage = Main.main();
            window1Stage.setScene(window1Scene);
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}