How to pass values to already opened Stage(First Contrller) from Second Controller?

Question

I've two Controllers

1. FXMLDocumentController has TableView CustomerTable.
2. NewCustomerController a second Controller to add a new row.

Here is my code

FXMLDocument.fxml

<AnchorPane id="AnchorPane" prefHeight="283.0" prefWidth="437.0" xmlns="http://javafx.com/javafx/8.0.171" xmlns:fx="http://javafx.com/fxml/1" fx:controller="mytableview.FXMLDocumentController">
    <children>
        <Button fx:id="button" layoutX="309.0" layoutY="25.0" onAction="#handleButtonAction" text="New Customer" />
      <TableView fx:id="customerTable" layoutX="6.0" layoutY="61.0" prefHeight="215.0" prefWidth="426.0">
        <columns>
          <TableColumn fx:id="custname" prefWidth="75.0" text="Customer Name" />
          <TableColumn fx:id="city" prefWidth="75.0" text="City" />
        </columns>
         <columnResizePolicy>
            <TableView fx:constant="CONSTRAINED_RESIZE_POLICY" />
         </columnResizePolicy>
      </TableView>
    </children>
</AnchorPane>  

NewCustomer.fxml

<AnchorPane id="AnchorPane" prefHeight="172.0" prefWidth="209.0" xmlns:fx="http://javafx.com/fxml/1" xmlns="http://javafx.com/javafx/8.0.171" fx:controller="com.newcustomer.NewCustomerController">
   <children>
      <Button layoutX="141.0" layoutY="129.0" mnemonicParsing="false" onAction="#newCustomer" text="Add" />
      <TextField fx:id="cNameTextField" layoutX="14.0" layoutY="26.0" promptText="Customer Name" />
      <TextField fx:id="custCityTextField" layoutX="14.0" layoutY="77.0" promptText="City" />
   </children>
</AnchorPane>

FXMLDocumentController.java

public class FXMLDocumentController implements Initializable {

private FXMLDocumentController documentController; //updated

@FXML
public TableView<Customer> customerTable;

@FXML
public TableColumn<Customer, String> custname;

@FXML
public TableColumn<Customer, String> city;  

@Override
public void initialize(URL url, ResourceBundle rb) { //updated
    custname.setCellValueFactory(new PropertyValueFactory<>("name"));
    city.setCellValueFactory(new PropertyValueFactory<>("city"));           
}

@FXML
private void handleButtonAction(ActionEvent event) throws IOException {
    Parent parent = FXMLLoader.load(getClass().getResource("/com/newcustomer/NewCustomer.fxml"));
    controller.setFXMLDocumentController(documentController); //updated
    Stage stage = new Stage();
    Scene scene = new Scene(parent);
    stage.setScene(scene);
    stage.show();
}

public void inflateUI(Customer customer) {
    custname.setCellValueFactory(new PropertyValueFactory<>("name"));
    city.setCellValueFactory(new PropertyValueFactory<>("city"));
    customerTable.getItems().add(customer);
}

NewCustomerController.java

public class NewCustomerController implements Initializable { 

 private FXMLDocumentController documentController; //updated

@FXML
private TextField cNameTextField;

@FXML
private TextField custCityTextField;

@Override
public void initialize(URL url, ResourceBundle rb) {
}
    public void setFXMLDocumentController(FXMLDocumentController fXMLDocumentController) { //updated
    this.documentController = fXMLDocumentController;
}

public void newCustomer(ActionEvent e) throws IOException {
    String name = cNameTextField.getText();
    String stringCity = custCityTextField.getText();

    Customer customer = new Customer(10, name, stringCity);
    FXMLLoader fXMLLoader = new FXMLLoader(getClass().getResource("/mytableview/FXMLDocument.fxml"));
    documentController = fXMLLoader.<FXMLDocumentController>getController(); //Newly updated
    documentController.inflateUI(customer); // Newly updated 
    }

}

MyTableView.java

public class MyTableView extends Application {

    public MyTableView() {
    }

    @Override
    public void start(Stage stage) throws Exception {
        Parent root = FXMLLoader.load(getClass().getResource("FXMLDocument.fxml"));

        Scene scene = new Scene(root);

        stage.setScene(scene);
        stage.show();
    }

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

}

I want a row to be added in a TableView but it does not working.
What the exact I've missed?

Answer 1

Firstly, I recommend to go through the link provided by @kleopatra to understand the concepts of communication between controllers.

Coming to your actual question, I noticed three issues in your code. Among which, one is already specified by @kleopatra.

Regarding the NPE you are getting in newCustomer() method, you initiated the FXMLLoader instance but not loading it. For this reason the getController() is null. To fix this you need to first call the load() method before calling the getController().

public void newCustomer(ActionEvent e) throws IOException {
    String name = cNameTextField.getText();
    String stringCity = custCityTextField.getText();
    Customer customer = new Customer(10, name, stringCity);
    FXMLLoader fXMLLoader = new FXMLLoader(getClass().getResource("/mytableview/FXMLDocument.fxml"));
    fXMLLoader.load(); // YOU ARE MISSING THIS LINE
    FXMLDocumentController fXMLDocumentController = fXMLLoader.<FXMLDocumentController>getController();
    fXMLDocumentController.inflateUI(customer); // Getting NPE at this line.
}

However, the above fix is USELESS because you are creating a new instance of FXMLDocumentController that is not being used (as specified by @kleopatra). You have to actually pass the controller instance to which you want to communicate. You need to create an instance variable of this controller in NewCustomerController and set to it.

@FXML
private void handleButtonAction(ActionEvent event) throws IOException {
    FXMLLoader fXMLLoader = new FXMLLoader(getClass().getResource("/com/newcustomer/NewCustomer.fxml"));
    Parent parent = fXMLLoader.load();
    NewCustomerController controller = fXMLLoader.getController();
    controller.setFXMLDocumentController(this); // Pass this controller to NewCustomerController
    Stage stage = new Stage();
    Scene scene = new Scene(parent);
    stage.setScene(scene);
    stage.show();
}

NewCustomerController.java

private FXMLDocumentController fXMLDocumentController;

public void setFXMLDocumentController(FXMLDocumentController fXMLDocumentController) {
    this.fXMLDocumentController = fXMLDocumentController;
}

public void newCustomer(ActionEvent e) throws IOException {
    String name = cNameTextField.getText();
    String stringCity = custCityTextField.getText();
    Customer customer = new Customer(10, name, stringCity);
    fXMLDocumentController.inflateUI(customer);//You are passing to the currently loaded controller
}

Lastly, you need to set the CellValueFactory only once to the TableColumns, not everytime you set the customer. You can move those two lines to initialize() method.

@Override
public void initialize(URL url, ResourceBundle rb) {
    custname.setCellValueFactory(new PropertyValueFactory<>("name"));
    city.setCellValueFactory(new PropertyValueFactory<>("city"));
}