更改侦听器错误javafx

Question

请帮忙！我用javafx FXML创建了一个tableview并填充了它。我还编写了一个代码，以便能够将所选行的值提取到另一个FXML文件中。问题是，当我选择任何行时，它只为我选择的每一行提取表视图第一行的值。下面是填充tableview和行选择的代码。

    public class ViewController implements Intializable{
    @FXML private TableView<Employee,String>viewEmployee;
    @FXML private TableColumn<Employee,String>staff;
    @FXML private TableColumn<Employee,String>sur;
    @FXML private TableColumn<Employee,String>first;
    observableList<Employee>data =FXCollections.observablArrayList();
    Connection conn;
    PreparedStatement pstmt=null;
    ResultSet rs=null;

    @Override
    public void initialize(URL location,ResourceBundle resources){
    try{
       Class.forName("org.apache.deby.jdbc.ClientDriver");
       conn=DriverManager.getConnection("jdbc:derby://localhost:1527/Employee");
       String rest="select * from Employee";
       pstmt=conn,prepareStatement(rest);
       rs=pstmt.executeQuery();

       while(rs.next()){
             data.add(new Employee(
                    rs.getString("staffid"),
                    rs.getString("surname"),
                    rs.getString("firstname"),
                    ));

    staff.setcellValueFactory(newPropertyValueFactory<>("StaffId"));

    viewEmployee.setItems(data);
    viewEmployee.getSelectedModel().selectedItemProperty().addListener(new   ChangeListener<Employee>(){
    @Override
    public void changed(ObservableValue<?extends employee> observable,Employee   oldValue, Employee newValue){
    if (newValue !=null){
    try{
    Stage stage =new stage();
    Parent root =FXMLLoader.load(getClaa().getResource("Staff.fxml")
    Scene scene =new Scene(root);
    stage.setScene(scene);
    stage.show();
}catch(IOException ex){
}
}
}
});

}
}catch (ClassNotFoundException |SQLException ex{

}
}
}