Develop Reference

Cannot invoke "javafx.scene.control.ComboBox.getItems()" because the return value of "Controller.getMyBox()" is null

Somehow, I cannot add items to my ComboBox variable from another class as it always says either the value of variable is null or the return value of its getter is null.
I use Scene Builder to build Sample.fxml, with controller as Controller class, luanch the whole thing form UserInterface class
FXML
<?xml version="1.0" encoding="UTF-8"?>
<?import javafx.scene.control.ComboBox?>
<?import javafx.scene.layout.BorderPane?>
<BorderPane xmlns="http://javafx.com/javafx/11.0.1" xmlns:fx="http://javafx.com/fxml/1" fx:controller="Controller">
<center>
<ComboBox fx:id="myBox" prefWidth="150.0" BorderPane.alignment="CENTER" />
</center>
</BorderPane>
Controller
public class Controller {
#FXML
private ComboBox<String> myBox;
public ComboBox<String> getMyBox() {
return myBox;
}
public void initialize() {
ObservableList<String> defaultTicker = FXCollections.observableArrayList("Something");
myBox.getItems().addAll(defaultTicker);
}
}
UserInterface
public class UserInterface extends Application {
#Override
public void start(Stage primaryStage) {
try {
FXMLLoader loader = new FXMLLoader(getClass().getResource("Sample.fxml"));
Parent root = loader.load();
Controller controller = new Controller();
primaryStage.setTitle("Title");
primaryStage.setScene(new Scene(root));
primaryStage.show();
List<String> addStuff = new ArrayList<String>();
addStuff.add("a");
addStuff.add("b");
addStuff.add("c");
controller.getMyBox().getItems().addAll(addStuff);
} catch (Exception e) {
e.printStackTrace();
}
}
public static void main(String[] args) {
launch(args);
}
}
After running, the interface appears, with only the option "Something" in it. So I guess it initialize fine?
The interface after launch
What did I do wrong? I couldn't seem to find any solutions so far.
Thanks in advance.

CallBack method implementation needed

I have a root screen which generates a popup and in popup I have a listview with button on it and I want to update the texfield in root screen and close the popupwindow when a button is clicked in popup. Code for popup and its controller.
POPUP
public void display() throws IOException {
Stage window =new Stage();
FXMLLoader loader=new FXMLLoader();
Parent root = loader.load(getClass().getResource("/ProfilePopup.fxml"));
window.setTitle("Your profile");
window.setScene(new Scene(root, 400, 500));
window.show();
}
PopUPController
public void initialize() {
listView.setEditable(true);
listView.setVisible(true);
listView.setItems(walletModel.myWallets);
listView.setCellFactory(param -> {
try {
return new EditableCell();
} catch (IOException e) {
e.printStackTrace();
}
return null;
});
listView.layout();
addWalletButton.setOnMouseClicked(event -> {
walletModel.createWallet();
listView.getFixedCellSize();
size.setText("Total Wallets: " + walletModel.walletSize());
});
if (walletModel.myWallets.size() == 0) {
walletModel.initializeWalletData();
walletModel.myWallets.add(walletModel.initializeWalletData());
}
size.setText("Wallet Size " + walletModel.walletSize());
}
static class EditableCell extends ListCell<WalletModel.WalletData> {
private final WalletCellController controller;
EditableCell() throws IOException {
FXMLLoader loader = new FXMLLoader(getClass().getResource("/selectButton.fxml"));
Node graphic = loader.load();
controller = loader.getController();
setGraphic(graphic);
}
#Override
protected void updateItem(WalletModel.WalletData item, boolean empty) {
if (empty) {
controller.rootView.setVisible(false);
} else {
controller.textField.setText(item.getName());
controller.rootView.setVisible(true);
}
}
}
}
I want the button on listview to update the root screen when its clicked and plus close the popup as well. Each listview is getting graphics from walletcellcontroller code below.
Here is how I am calling from the root screen.
Creating instance in root screen and then calling
(Popup popup=new Popup();)
public void popupOpen() throws IOException {
popup.display();
}
here is the code for listview item
public class WalletCellController implements OnClick {
public Button select;
public TextField textField;
public AnchorPane rootView;
public void initialize(){
onMouseClicked();
}
public void onMouseClicked() {
select.setOnAction(closeEvent -> {
Node source = (Node) closeEvent.getSource();
Stage stage = (Stage) source.getScene().getWindow();
stage.close();
});
}}
Can you tell me how to use the callbacks for actionevents here. I think I need call back from POPUP Controller to POPup and then from POPup to root screen.
I am new in java so I not sure about the implementation of it.

interface Callable {
public void callBackMethod();
}
class Worker {
// Worker gets a handle to the boss object via the Callable interface.
// There's no way this worker class can call any other method other than
// the one in Callable.
public void doSomeWork(Callable myBoss) {
myBoss.callBackMethod();
// ERROR!
//myBoss.directMethod();
}
}
class Boss implements Callable {
public Boss() {
// Boss creates a worker object, and tells it to do some work.
Worker w1 = new Worker();
// Notice, we're passing a reference of the boss to the worker.
w1.doSomeWork(this);
}
//developer that develop library just call controll the place of calling
public void callBackMethod() {
System.out.println("What do you want?");
}
public void directMethod() {
System.out.println("I'm out for coffee.");
}
}
public class Main {
public static void main(String[] args) {
Boss b = new Boss();
b.directMethod();
// write your code here
}
}
this is sample code of call back method

In cases like these I recommend using Dialog, since it allows you to query & wait for user input.
Example
<?xml version="1.0" encoding="UTF-8"?>
<?import javafx.scene.control.Dialog?>
<?import javafx.scene.control.DialogPane?>
<?import javafx.scene.control.Button?>
<?import javafx.scene.layout.VBox?>
<Dialog xmlns:fx="http://javafx.com/fxml/1" fx:id="dialog" fx:controller="fxml.DialogController">
<dialogPane>
<DialogPane headerText="Choose item!">
<content>
<VBox prefWidth="100" spacing="5">
<children>
<Button text="a" onAction="#choice" maxWidth="Infinity" />
<Button text="b" onAction="#choice" maxWidth="Infinity" />
<Button text="c" onAction="#choice" maxWidth="Infinity" />
<Button text="Cancel" onAction="#cancel" maxWidth="Infinity" />
</children>
</VBox>
</content>
</DialogPane>
</dialogPane>
</Dialog>
public class DialogController {
#FXML
private Dialog<String> dialog;
#FXML
private void choice(ActionEvent event) {
Button source = (Button) event.getSource();
dialog.setResult(source.getText());
dialog.close();
}
#FXML
private void cancel() {
dialog.setResult("");
dialog.close();
}
}
#Override
public void start(Stage primaryStage) {
TextField textField = new TextField();
Button btn = new Button("Choose");
btn.setOnAction((ActionEvent event) -> {
Dialog<String> dialog;
try {
dialog = FXMLLoader.load(getClass().getResource("/fxml/Dialog.fxml"));
} catch (IOException ex) {
throw new IllegalStateException(ex);
}
Optional<String> result = dialog.showAndWait();
if (!result.orElse("").isEmpty()) {
textField.setText(s);
}
});
VBox root = new VBox(textField, btn);
Scene scene = new Scene(root);
primaryStage.setScene(scene);
primaryStage.show();
}

Change Label depending on boolean JavaFX

I am super new to JavaFX and for my checkers game I want to display who's turn it is above my board. I have read through multiple very similar questions, but it doesn't seem to get me where I want to go. I hope you can help me!
I have a FXML file with the following code:
<HBox fx:id="topBox" alignment="TOP_CENTER" prefHeight="45.0" prefWidth="200.0" spacing="10.0" BorderPane.alignment="CENTER" xmlns="http://javafx.com/javafx/8" xmlns:fx="http://javafx.com/fxml/1" fx:controller="application.SampleController">
<children>
<Label fx:id="labelTurn" text="test" />
<Button fx:id="buttonResign" alignment="CENTER" mnemonicParsing="false" onAction="#doResign" prefHeight="25.0" prefWidth="80.0" text="Resign" />
</children>
</HBox>
In my main:
public class Main extends Application {
Checkers content = new Checkers();
BorderPane border = new BorderPane();
#Override
public void start(Stage primaryStage) throws Exception {
try {
border.setTop(FXMLLoader.load(getClass().getResource("Sample.fxml")));
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
border.setCenter(createContent());
Scene scene = new Scene(border);
primaryStage.setTitle("Checkers from main");
primaryStage.setScene(scene);
primaryStage.show();
}
public static void main(String[] args) {
launch(args);
}
}
My controller:
public class SampleController {
#FXML
private Label labelTurn;
#FXML
private HBox topBox;
#FXML
private Button buttonResign;
private Checkers content = new Checkers();
#FXML
void doResign(ActionEvent event) {
content.resign();
// System.exit(0); //TODO eine tatsächliche Methode eingeben!!
}
public void setLabelTurn(Label labelTurn) {
this.labelTurn = labelTurn;
String setLabelText() {
String s = " ";
if (content.getWhiteTurnPropValue()) {
labelTurn.setText("White, it is your turn.");
s = "White, it is your turn.";
return s;
} else {
labelTurn.setText("Black, it is your turn.");
s = "Black, it is your turn.";
return s;
}
}
#FXML
void initialize() {
assert buttonResign != null : "fx:id=\"buttonResign\" was not injected: check your FXML file 'Sample.fxml'.";
assert topBox != null : "fx:id=\"topBox\" was not injected: check your FXML file 'Sample.fxml'.";
assert labelTurn != null : "fx:id=\"labelTurn\" was not injected: check your FXML file 'Sample.fxml'.";
labelTurn.textProperty().setValue(setLabelText());
}
}
My game data has a BooleanProperty to show who's turn it is. It gets changed after every successful move.
BooleanProperty whiteTurnProp = new SimpleBooleanProperty(true);
public BooleanProperty getWhiteTurnProp() {
return whiteTurnProp;
}
public void setWhiteTurnPropValue(Boolean whiteTurn) {
this.whiteTurnProp.setValue(whiteTurn);
}
public boolean getWhiteTurnPropValue() {
return this.whiteTurnProp.getValue();
}
As far as I have understood, I need to bind the Label to the value, which I have done in the initialize method. But when I play and the value in my game class changed, the label stays the same. How do I update the label? I think I need to add a change listener to something, but I dont know how to do that and more specifically WHERE.
Thank you so much for your help! I shortened my code a bit and hope it is still not too long.
Best,
Lisa

In initialize: labelTurn.textProperty().setValue(setLabelText()); is not a binding, it is a simple set on the property. A really strange one as setLabelText() sets the text of the Label and also return the string which was set, which value is used again to the text of the Label.
You could create a real binding instead:
labelTurn.textProperty().bind(Bindings.createStringBinding(() -> {
String s = " ";
if (content.getWhiteTurnProp().get())
s = "White, it is your turn.";
else
s = "Black, it is your turn.";
return s;
}, content.getWhiteTurnProp()));

How to I get the Scene of another UI interface - Javafx 8

I am new to JavafX. I wanted to change the CSS file of my first GUI through the second one.
I have the following code:
Main1.java
package javafxapplication3.a;
import javafx.application.Application;
import javafx.fxml.FXMLLoader;
import javafx.scene.Parent;
import javafx.scene.Scene;
import javafx.stage.Stage;
public class Main1 extends Application{
public static void main(String[] args) {
launch(args);
}
#Override
public void start(Stage primaryStage) throws Exception {
Parent root = null;
try {
root = FXMLLoader.load(getClass().getResource("/main1.fxml"));
} catch (Exception e) {
}
String css = Main1.class.getResource("/main1.css").toExternalForm();
Scene scene = new Scene(root, 400, 400);
scene.getStylesheets().clear();
scene.getStylesheets().add(css);
primaryStage.setResizable(false);
primaryStage.setScene(scene);
primaryStage.setTitle("JCal");
primaryStage.show();
}
}
Main1Controller.java
package javafxapplication3.a;
import javafx.fxml.FXML;
import javafx.fxml.FXMLLoader;
import javafx.scene.Parent;
import javafx.scene.Scene;
import javafx.scene.control.Button;
import javafx.stage.Stage;
public class Main1Controller {
#FXML
private Button button1;
public void initialize() {
button1.setOnAction(value -> {
Stage primaryStage = new Stage();
Parent root = null;
try {
root = FXMLLoader.load(getClass().getResource("/main2.fxml"));
} catch (Exception e) {
}
Scene scene = new Scene(root, 400, 400);
primaryStage.setResizable(false);
primaryStage.setScene(scene);
primaryStage.setTitle("JCal");
primaryStage.show();
});
}
}
main1.fxml
<AnchorPane maxHeight="-Infinity" maxWidth="-Infinity" minHeight="-Infinity" minWidth="-Infinity" prefHeight="400.0" prefWidth="600.0" xmlns="http://javafx.com/javafx/8.0.40" xmlns:fx="http://javafx.com/fxml/1" fx:controller="javafxapplication3.a.Main1Controller">
<children>
<Button fx:id="button1" layoutX="271.0" layoutY="173.0" mnemonicParsing="false" text="Main-1" />
</children>
</AnchorPane>
main2.fxml
<AnchorPane maxHeight="-Infinity" maxWidth="-Infinity" minHeight="-Infinity" minWidth="-Infinity" prefHeight="400.0" prefWidth="600.0" xmlns="http://javafx.com/javafx/8.0.40" xmlns:fx="http://javafx.com/fxml/1" fx:controller="javafxapplication3.a.Main2Controller">
<children>
<Button fx:id="button" layoutX="271.0" layoutY="173.0" mnemonicParsing="false" text="Main-2" />
</children>
</AnchorPane>
In the FXML I have a Button called button1, when ever I click on it, it opens a new GUI which has another button in it called button. In the end what I wanted to do was that when ever I click on the second button i.e. button the colour of the button in the primary GUI should change should change.
I did try getting the controllers shown in this example, But this dint help me.
Do I need to create a second controller and create a new stage and scene all together? or is there any alternative way to it?

In the controller for your main2.fxml, provide a mechanism in it for setting an action to be executed when the button is pressed. For example:
public class Main2Controller {
#FXML
private Button button ;
private Runnable buttonAction = () -> {} ; // do nothing by default
public void setButtonAction(Runnable action) {
this.buttonAction = action ;
}
public void initialize() {
button.setOnAction(e -> buttonAction.run());
}
}
Now in your Main1Controller you can retrieve the controller when you load the FXML, and set the button action:
button1.setOnAction(value -> {
Stage primaryStage = new Stage();
Parent root = null;
try {
FXMLLoader loader = new FXMLLoader(getClass().getResource("/main2.fxml"));
root = loader.load();
Main2Controller controller = loader.getController();
controller.setButtonAction(() -> {
// perform button action here...
});
} catch (Exception e) {
e.printStackTrace();
}
Scene scene = new Scene(root, 400, 400);
primaryStage.setResizable(false);
primaryStage.setScene(scene);
primaryStage.setTitle("JCal");
primaryStage.show();
});
An alternative approach is to let both controllers have access to the same observable state, e.g. an ObjectProperty<Color>. This approach might be better if you have a lot of actions in one controller that affect state elsewhere (you just bundle all the data into a single "model" class that you pass). This looks like:
public class Main1Controller {
private final ObjectProperty<Color> color = new SimpleObjectProperty<>();
#FXML
private Button button1;
public void initialize() {
color.addListener((obs, oldColor, newColor) -> {
String style = String.format("-fx-background-color: #%02x%02x%02x;",
(int) (newColor.getRed() * 255),
(int) (newColor.getGreen() * 255),
(int) (newColor.getBlue() * 255));
button1.setStyle(style);
});
button1.setOnAction(value -> {
Stage primaryStage = new Stage();
Parent root = null;
try {
FXMLLoader loader = new FXMLLoader(getClass().getResource("/main2.fxml"));
root = loader.load();
Main2Controller controller = loader.getController();
controller.setColorModel(color);
} catch (Exception e) {
e.printStackTrace();
}
Scene scene = new Scene(root, 400, 400);
primaryStage.setResizable(false);
primaryStage.setScene(scene);
primaryStage.setTitle("JCal");
primaryStage.show();
});
}
}
and Main2Controller looks like
public class Main2Controller {
#FXML
private Button button ;
private ObjectProperty<Color> colorModel = new SimpleObjectProperty<>();
public void setColorModel(ObjectProperty<Color> color) {
this.colorModel = color ;
}
public void initialize() {
button.setOnAction(e -> {
colorModel.set(/* some color */);
});
}
}

JavaFX Dialogbox communication

I am new to JavaFX and trying to create an Confirmation Dialogbox.
I know already that there is no real build in dialogbox in JavaFX so I created one myself like this:
#FXML
public void delBox() {
try {
Stage dialogStage = new Stage();
AnchorPane root = FXMLLoader.load(getClass().getResource("Dialog.fxml"));
Scene scene = new Scene(root);
dialogStage.setScene(scene);
dialogStage.showAndWait();
} catch(Exception e) {
e.printStackTrace();
}
}
It looks pretty good already, but what I dont understand is, how those two Stages can communicate with each other? I want to pass a String to the dialog which is than shown in the message, also when one of the buttons in the dialog window is clicked I wanna react to this in the accordingly.
Can anyone explain me how communication between the stages works?
btw: I use .FXML files and controller classes.

You need a reference to the controller for the dialog. To do this, create an instance of FXMLLoader instead of using the static FXMLLoader.load(URL) method.
For example, suppose you have a class DialogController, so your Dialog.fxml looks like:
<AnchorPane xmlns:fx="..." fx:controller="DialogController.fxml">
...
</AnchorPane>
Then you can access the DialogController in the delBox() method above with
Stage dialogStage = new Stage();
FXMLLoader loader = new FXMLLoader(getClass().getResource("Dialog.fxml"));
AnchorPane root = (AnchorPane)loader.load();
DialogController controller = (DialogController) loader.getController();
Scene scene = new Scene(root);
dialogStage.setScene(scene);
dialogStage.showAndWait();
And now you can communicate between the two controllers. For example, in DialogController you could define a message property, and bind it to a Label :
public class DialogController {
private final StringProperty message = new SimpleStringProperty("");
public void setMessage(String message) {
this.message.set(message);
}
public String getMessage() {
return message.get();
}
public StringProperty messageProperty() {
return message ;
}
#FXML
private Label label ;
public void initialize() {
label.textProperty().bind(message);
// ...
}
}
And then back in your delBox() method:
//... as before:
AnchorPane root = (AnchorPane)loader.load();
DialogController controller = (DialogController) loader.getController();
controller.setMessage("Hello World");
// ...
Similarly, you can define properties which are set when controls are pressed in the dialog itself, and either observe them or query them after the showAndWait() call.
There are a bunch of other similar techniques. Some examples:
https://github.com/james-d/Shared-Data-Controller/tree/master/src
https://github.com/james-d/Dialog-FXML-Example/tree/master/src
https://github.com/james-d/Nested-Controller-Example/tree/master/src/nestedcontrollerexample

<AnchorPane xmlns:fx="..." fx:controller="DialogController.fxml">
...
</AnchorPane>
FX Controller is a java file, so it has to be DialogController and the Controller's path should be included i.e, fx:controller="applicationPackageName.DialogController"
The above mentioned fxml code does not work. It results in
javafx.fxml.LoadException
java.lang.InstantiationException
java.lang.NoSuchMethodException
Reason: The jvm looks for a class constructor with 0 parameters to build an instance. To overcome the error, the controller file needs to be loaded in the function coded in java:
loader.setController(new ControllerName(""));
To sum up (Working code):
FXML file:
<BorderPane id="background" maxHeight="-Infinity" maxWidth="-Infinity" minHeight="-Infinity" minWidth="-Infinity" prefHeight="240.0" prefWidth="320.0" xmlns="http://javafx.com/javafx/8" xmlns:fx="http://javafx.com/fxml/1" >
<bottom>
<HBox alignment="CENTER" prefHeight="100.0" prefWidth="200.0">
<children>
<Button onAction="#close" text="OK" />
</children>
</HBox>
</bottom>
<center>
<Label fx:id="messageLabel" />
</center>
</BorderPane>
Controller file:
public class PiPreferenceController {
private final String message ;
#FXML
private Label messageLabel ;
#FXML
void initialize() {
messageLabel.setText(message);
}
public PiPreferenceController(String message) {
this.message = message ;
}
#FXML
public void close() {
messageLabel.getScene().getWindow().hide();
}
}
Function:
void dialogPreferences() throws IOException {
Stage dialogStage = new Stage();
FXMLLoader loader = new FXMLLoader(getClass().getResource(
"PiPreference.fxml"));
loader.setController(new PiPreferenceController(""));
BorderPane root = (BorderPane) loader.load();
Scene scene = new Scene(root);
dialogStage.setScene(scene);
dialogStage.showAndWait();
}