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Variable value shows as null

variable recUsername is assigned with a value passed by another controller. But after initialization when recUsername is printed inside BtnClicked method, it prints null. why?
public class nextSceneController implements Initializable {
private String recUsername;
public void transferMessage(String message){
recUsername = message;
}
#FXML
private Button Btn;
#FXML
void BtnClicked(ActionEvent event) {
System.out.println(recUsername);
}
#Override
public void initialize(URL location, ResourceBundle resources) {
System.out.println(recUsername);
}
}
This is MenuController.java which is linked to menu.fxml
public class MenuController {
public MenuController() throws SQLException, ClassNotFoundException {
}
String orderRefNo = Key_Generator.getReferenceKey();
FXMLLoader loader = new FXMLLoader(getClass().getResource("orderList.fxml"));
Parent root = loader.load();
OrderListController orderListController = loader.getController();
orderListController.transferMessage(orderRefNo);
Stage orderListStage = new Stage();
orderListStage.setScene(new Scene(root));
orderListStage.show();
}
This is OrderListController which is linked to orderList.fxml
public class OrderListController implements Initializable {
public OrderListController() throws SQLException, ClassNotFoundException, IOException {
}
private String orderRefNoRec;
public void transferMessage(String message){
orderRefNoRec = message;
}
#Override
public void initialize(URL location, ResourceBundle resources) {
try{
PreparedStatement preparedStatement = connection.prepareStatement("SELECT `FoodName`, `Quantity`, `Price` FROM `orders` WHERE OrderRefNo='"+orderRefNoRec+"'");
ResultSet resultSet = preparedStatement.executeQuery();
while (resultSet.next()){
observableList.add(new orderListTableModel(resultSet.getString("FoodName"), resultSet.getString("Quantity"),
resultSet.getString("Price")));
}
} catch (SQLException e) {
e.printStackTrace();
}
food_OrderListTableModel.setCellValueFactory(new PropertyValueFactory<>("foodName"));
quantity_OrderListTableModel.setCellValueFactory(new PropertyValueFactory<>("qty"));
price_OrderListTableModel.setCellValueFactory(new PropertyValueFactory<>("price"));
orderListTableModel.setItems(null);
orderListTableModel.setItems(observableList);
}
}

This is a case where you need to illustrate out your program flow, to know when you are able to call up the set variable.
Below an illustration on where it probably goes wrong(Can't say for certain as I don't have access to the full code, but this is an oversimplification of the most likely issue at hand):
Your main scene controller creates a new nextScene.
The business logic then calls initialize to pass along all necessary resources etc...
You call print here, but transferMessage hasn't been called yet at this point, so the recUserMessage variable is still null.
You then probably call transferMessage, which sets the variable, but printing is then never called.
When you come across such a problem in the future, where something doesn't do what you think it should do, draw it out, step by step what you think is happening to pin point where things should happen and where your expectations should be adapted.

#FXML Annotation not working correctly

I'm currently working on a 'small' project with JavaFX. I used the SceneBuilder to create the first sketch of my GUI. it still needs some adjustment and styling but I wanted to see if it's working so far.
I have 2 hyperlinks on the GUI, if the user clicks one of them the default system-browser should open with a specific URL.
So far I got this:
Main.java:
public class Main extends Application {
#Override
public void start(Stage primaryStage) throws MalformedURLException, IOException {
DataBean dataBean= new DataBean(primaryStage);
Controller controller = new Controller(dataBean);
controller.show();
}
public static void main(String[] args) {
launch(args);
}
}
DataBean.java:
public class DataBean {
private Stage primaryStage;
public DataBean(Stage stage) {
primaryStage = stage;
}
public Stage getPrimaryStage() {
return primaryStage;
}
}
TestautomatView.java:
public class TestautomatView implements Initializable {
#FXML
private ComboBox<String> environmentCombo;
#FXML
private Hyperlink crhl;
#FXML
private Hyperlink help;
#Override
public void initialize(URL location, ResourceBundle resources) {
}
private Scene scene;
private BorderPane root;
public TestautomatView() throws MalformedURLException, IOException {
root = FXMLLoader.load(new URL(TestautomatView.class.getResource("Sample.fxml").toExternalForm()));
scene = new Scene(root);
}
public void show(Stage stage) {
stage.setTitle("CrossReport Testautomat");
stage.setScene(scene);
stage.show();
}
public ComboBox<String> getEnvironmentCombo() {
return environmentCombo;
}
public Hyperlink getCrhl() {
return crhl;
}
public Hyperlink getHelp() {
return help;
}
public Scene getScene() {
return scene;
}
}
In my controller I want to set the ActionHandler to the hyperlinks but it's not working because the getters in my view return null.
public class Controller {
private DataBean dataBean;
private TestautomatView view;
public Controller(DataBean databean) throws MalformedURLException, IOException {
this.dataBean = databean;
this.view = new TestautomatView();
setActionHandlers();
}
public void show() throws MalformedURLException, IOException {
view.show(dataBean.getPrimaryStage());
}
private void setActionHandlers() {
// setHyperlink(view.getCrhl(), "www.example.com");
// setHyperlink(view.getHelp(), "www.example2.com");
}
private void setHyperlink(Hyperlink hl, String uri) {
hl.setOnAction(new EventHandler<ActionEvent>() {
#Override
public void handle(ActionEvent event) {
//TODO - Open Default Browser
}
});
}
}
When I start my application, I can see the GUI but when I want to add the ActionHandlers I get a NullPointerException.
In the ´Sample.fxml´ file the hyperlinks are children of a HBox
<Hyperlink fx:id="crhl" text="Report" />
<Hyperlink fx:id="help" text="Help" />
But it's not just the hyperlinks even the ComboBox is null when I inspect my app in the debugger.
Where is my mistake?

The problem is that you are creating your controller manually by using new TestautomatView(). It must be created by FXMLLoader for annotations to work. You must also set fx:controller attribute in Sample.fxml to your controller (TestautomatView) fully qualified class name.
Example code:
FXMLLoader fl = new FXMLLoader(new URL(TestautomatView.class.getResource("Sample.fxml").toExternalForm()));
root = fl.load();
TestautomatView controller = fl.getController();
PS: You should rename your TestautomatView to TestautomatController. FXML file is your "view".

As pointed out in another answer, the issue is that you create an instance of TestautomatView "by hand". The default behavior of the FXMLLoader is to create an instance of the controller class specified in the FXML file, and use that instance as the controller. Consequently, you have two instances of TestautomatView: the one you created (and have a reference to), and the one that was created by the FXMLLoader. It is the second one that has the #FXML-annotated fields initialized.
You can change this default behavior by creating an FXMLLoader instance, and setting the controller on it directly. E.g. consider doing:
public class TestautomatView implements Initializable {
#FXML
private ComboBox<String> environmentCombo;
#FXML
private Hyperlink crhl;
#FXML
private Hyperlink help;
#Override
public void initialize(URL location, ResourceBundle resources) {
}
private Scene scene;
private BorderPane root;
public TestautomatView() throws MalformedURLException, IOException {
FXMLLoader loader = new FXMLLoader(TestautomatView.class.getResource("Sample.fxml"));
loader.setController(this);
root = loader.load();
scene = new Scene(root);
}
// etc...
}
Since you are directly setting the controller, you need to remove the fx:controller attribute from the Sample.fxml file for this to work.
You may also be interested in this pattern, which is quite similar (though not exactly the same) as what you are trying to do here.

Auto Updating Tableview in JAVA Fx

In my project when a client will be disconnected, server will delete the name from observable list and the tableview should stop showing the name. But the tableview is not updating.
Controller class
public class Controller {
#FXML
public TableView tableView;
#FXML
private TableColumn<clientLoginData,String> client;
#FXML
private TableColumn<clientLoginData,String> activeTime;
void initialize(ObservableList<clientLoginData> data)
{
client.setCellValueFactory(new PropertyValueFactory<>("clientName"));
client.setCellFactory(TextFieldTableCell.<clientLoginData>forTableColumn());
activeTime.setCellValueFactory(new PropertyValueFactory<>("time"));
activeTime.setCellFactory(TextFieldTableCell.<clientLoginData>forTableColumn());
tableView.setItems(data);
tableView.setEditable(true);
}
}
main class
public class Main extends Application{
volatile public ObservableList<clientLoginData> data= FXCollections.observableArrayList();
public Controller controller;
#Override
public void start(Stage primaryStage) throws Exception {
FXMLLoader loader = new FXMLLoader();
loader.setLocation(getClass().getResource("server.fxml"));
Parent root = loader.load();
data.addAll(new clientLoginData((new SimpleStringProperty("john")),new SimpleStringProperty(ZonedDateTime.now().getHour()+":"+ZonedDateTime.now().getMinute())));
controller=loader.getController();
controller.initialize(data);
primaryStage.setTitle("Server");
primaryStage.setScene(new Scene(root, 600, 400));
primaryStage.show();
Thread t=new Thread(new messengerServer(this));
t.start();
}
public static void main(String[] args) {
launch(args);
}
}
updating class
public class messengerReadThread implements Runnable {
private Thread thr;
private NetworkUtil nc;
public Hashtable<SimpleStringProperty, NetworkUtil> table;
SimpleStringProperty oldName;
Main main;
public messengerReadThread(NetworkUtil nc, Hashtable<SimpleStringProperty, NetworkUtil> table, SimpleStringProperty s, Main main) {
this.nc = nc;
this.thr = new Thread(this);
thr.start();
this.table=table;
oldName=s;
this.main=main;
}
public void run() {
try {
while(true) {
String s1=(String)nc.read();
StringTokenizer st=new StringTokenizer(s1);
if(st.nextToken().equals("Name"))
{
String sn=s1.substring(5,s1.length());
NetworkUtil n1=table.get(oldName);
table.remove(oldName);
oldName=new SimpleStringProperty(sn);
table.put(oldName, n1);
main.data.add(new clientLoginData(oldName,new SimpleStringProperty(ZonedDateTime.now().getHour()+":"+ZonedDateTime.now().getMinute())));
}
else
{
System.out.println("here it is"+s1);
}
}
} catch(Exception e) {
System.out.println("disconnected "+oldName.toString());
main.data.remove(oldName);
//System.out.println(main.data.contains(oldName));
main.controller.tableView.refresh();//the tableview should update
}
nc.closeConnection();
}
}

There are some modification I should to to that code, like avoid using those "static references", by defining the ObservableList and move your Updating Code inside Controller so you can have a 2 classes code, the Main Class and your Controller... but i'll try to keep it simple.
First, you need to define the ObservableList inside you controller.
Then place your "updating" code inside the controller in a method. I suggest you to use a Task<> to keep your controller updated in the JavaFX Thread.
Try something like this:
private void updateTable(){
Task<Void> myUpdatingTask=new Task<Void>() {
#Override
protected Void call() throws Exception {
//Your Updating Code Here
}
}
//and then you run it like this:
Thread hilo=new Thread(myUpdatingTask);
hilo.setDaemon(true);
hilo.start();
}
Then, remove the parameter from your Initialize Method and define it private with the #FXML annotation like this:
#FXML
private void initialize(){
//Your Stuff to initialize
//here is were you fill your table like you did in the Main
//and don't forget to call you updateTable Method
this.updateTable();
}

Since this a dirty hack as pointed out by #kleopatra I am going to decorate it as a dirty hack.
****************************Dirty Hack*****************************************
Try hiding a column and displaying it again and your tableview should refresh

Set Reference Application from Controller?

New to JAVAFX so this maybe a simple fix, but I have controllers in my application setup using FXML files. I reference the controller to use via the FXML file and to load the file i use the following code in my Application class
private void replaceScene(String resource) {
try {
FXMLLoader loader = new FXMLLoader(getClass().getResource(resource));
Pane screen = (Pane) loader.load();
Scene scene = new Scene(screen);
scene.getStylesheets().addAll(getClass().getResource("/css/application.css").toExternalForm());
stage.setScene(scene);
stage.sizeToScene();
IControlledScreen controller = (IControlledScreen) loader.getController();
controller.setApp(this);
} catch (Exception e) {
System.out.println("Cannot load resource " + resource);
System.out.println(e.getMessage());
}
}
And here is a basic controller
public class MyController implements IControlledScreen {
MyApplication app;
public void setApp(MyApplication application) {
app = application;
}
#FXML
public Button btnStart;
// Initialises the controller class.
#FXML
protected void initialize() {
btnStart.setOnAction(new EventHandler<ActionEvent>() {
#Override
public void handle(ActionEvent arg0) {
// code here
}
});
}
}
I have also got an interface called IControlledScreen to set the reference to the application
public interface IControlledScreen {
// ALlows us a reference to the application
public void setApp(MyApplication app);
}
Now this all works fine, until i try to access the app variable during the initialize event. So changing the above controller to this now breaks, because app = NULL.
public class MyController implements IControlledScreen {
MyApplication app;
public void setApp(MyApplication application) {
app = application;
}
#FXML
public Button btnStart;
// Initialises the controller class.
#FXML
protected void initialize() {
// HERE app = NULL
app.GetSomeProperty = "";
}
}
How can i get round this?

Well I think you have to change your design.
The initialize method is called during FXMLLoader.load()
So the call stack would be something like
..replaceScene
..loader.load
....MyController.initialize()
..loader.getController
..controller.setApp(app)
If you really have to access the application from inside your controller you would need to make it a singleton.

Add data to static ComboBox in JavaFX 2.2

I just can't figure out how to add data to static ComboBox in JavaFX 2.2. Whatever I try to do ComboBox is empty. Here is the code:
#FXML private MenuItem menuItemNewTile;
#FXML private static ComboBox<Tile> comboBoxTileList;
#FXML
private void menuItemNewTileSetOnAction(ActionEvent event) throws IOException {
Parent root = FXMLLoader.load(getClass().getResource(TILE_WINDOW_URL));
Scene scene = new Scene(root);
Stage tileStage = new Stage();
tileStage.setScene(scene);
tileStage.show();
}
#FXML
private void comboBoxTileListSetOnAction(ActionEvent event) {
}
#Override
public void initialize(URL arg0, ResourceBundle arg1) {
comboBoxTileList = new ComboBox<>();
}
public static void refreshTileList(Tile tile) {
comboBoxTileList.getItems().add(tile);
}
If ComboBox is private, and I add item in initialize method it's working, but with static ComboBox I tried million things and still no progress.

Solution
Don't use static and #FXML together.
Rework your design so that the static keyword is no longer required for the comboBoxTileList and use an instance variable instead.
Additional Issue
An #FXML member such as comboBoxTileList should never be set to a new value, so you should not have comboBoxTileList = new ComboBox<>();
Answer to additional questions
I use another window to create new Tile object and from controller class of that window i call refreshTileList method. How to do that without using static?
There are numerous ways of writing your code so that you don't need a static reference to controller members. Here is a sample based on a solution from: Passing Parameters JavaFX FXML. You will need to modify the example to fit your exact case, it's just presented to demonstrate a possible pattern that you could use.
You can construct a new controller in code, passing any parameters you want from your caller into the controller constructor. Once you have constructed a controller, you can set it on an FXMLLoader instance before you invoke the load() instance method.
To set a controller on a loader (in JavaFX 2.x) you CANNOT also define a fx:controller attribute in your fxml file.
class ComboController {
#FXML private static ComboBox<Tile> comboBoxTileList;
public void refreshTileList(Tile tile) {
comboBoxTileList.getItems().add(tile);
}
}
class AnotherController {
#FXML private Button createTile;
#FXML private Button newCombo;
#FXML private StackPane mainPane;
private comboController;
#FXML private void createTile(ActionEvent event) {
if (comboController == null) {
return;
}
comboController.refreshTileList(
new Tile()
);
}
#FXML private void newCombo(ActionEvent event) {
try {
comboController = new ComboController();
FXMLLoader loader = new FXMLLoader(
getClass().getResource(
"combo.fxml"
)
);
loader.setController(comboController);
Pane comboPane = (Pane) loader.load();
mainPane.getChildren().setAll(comboPane);
} catch (IOException e) {
// handle exception.
}
}
}