JavaFX milti-windows异常

Question

我发现了这样的问题： 有一个MainWindow和2个SubWindows，但我有例外：

-Exception in thread "JavaFX Application Thread" java.lang.RuntimeException: java.lang.reflect.InvocationTargetException

-Caused by: java.lang.NullPointerException: Location is required.

-[...]

-at ApplicationForTests.SubWin1.SubWin1.display(SubWin1.java:14) 

> Parent root = FXMLLoader.load(getClass().getResource("ApplicationForTests/SubWin1UI.fxml"));

-[...]

-at ApplicationForTests.MainController.openSub1(MainController.java:22)

> subWin1.display();

-[...]

-Exception in thread "Thread-3" java.lang.IncompatibleClassChangeError

主：

public class Main extends Application {
public static BdcsDAO db = new BdcsDAO();

@Override
public void start(Stage primaryStage) throws Exception{
    Parent root = FXMLLoader.load(getClass().getResource("MainUI.fxml"));
    primaryStage.setTitle("Main window");
    primaryStage.setScene(new Scene(root, 500, 400));
    primaryStage.show();
    db.connect();
}

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

MainController：

public class MainController {
@FXML
Button button1;
@FXML
Button button2;
@FXML
public void openSub1() {
    SubWin1 subWin1 = new SubWin1();
    try {
        subWin1.display();
    } catch (IOException e) {
        e.printStackTrace();
    }
}
@FXML
public void openSub2() {
    SubWin2 subWin2 = new SubWin2();
    try {
        subWin2.display();
    } catch (IOException e) {
        e.printStackTrace();
    }
}
}

MainUI：

<AnchorPane prefHeight="400.0" prefWidth="600.0" xmlns="http://javafx.com/javafx/8.0.121" xmlns:fx="http://javafx.com/fxml/1" fx:controller="ApplicationForTests.MainController">
   <children>
      <Button fx:id="button1" onAction="#openSub1" layoutX="268.0" layoutY="185.0" mnemonicParsing="false" text="SubWin1" />
      <Button fx:id="button2" onAction="#openSub2" layoutX="268.0" layoutY="285.0" mnemonicParsing="false" text="SubWin2" />
   </children>
</AnchorPane>

SubWin1：

public class SubWin1 {
    public void display() throws IOException {
        Stage window = new Stage();
        Parent root = FXMLLoader.load(getClass().getResource("ApplicationForTests/SubWin1UI.fxml"));
        window.initModality(Modality.APPLICATION_MODAL);
        window.setTitle("Sub window no. 1");
        window.setScene(new Scene(root, 800, 500));
        window.show();
    }
}

SubWin1Controller：

public class SubWin1Controller {
    @FXML
    Button button;
    @FXML
    public void loadTableView() throws SQLException {
        setAlarmsTableView(Main.db.getSampleResultSet());
    }
    @FXML
    private TableView<AlarmType> alarmsTableView;
    @FXML
    private TableColumn<?, ?> columnDeviceIndex;
    @FXML
    private TableColumn<?, ?> columnAlgorithmType;
    private ObservableList<AlarmType> dataAlarms = FXCollections.observableArrayList();
    public void setAlarmsTableView(ResultSet rs) throws SQLException {
        columnDeviceIndex.setCellValueFactory(new PropertyValueFactory<>("deviceIndex"));
        columnAlgorithmType.setCellValueFactory(new PropertyValueFactory<>("algorithmType"));

        while (rs.next()) {
            dataAlarms.add(new AlarmType(rs.getInt(1), rs.getInt(2));
        }
        alarmsTableView.setItems(dataAlarms);
    }
}