JavaFX getController not updating FXML controller

Question

I have two controllers:

1. Main which contains TableView Tab which displays SQLITE database tables (which contain different number of columns) in tabular format, and
2. Rem which contains a button which dictates which database to display (there are many such controllers).

Now if I create a method in Main which is responsible for updating and displaying TableView contents, how do I use that method in other controller?

I created two static ObservableList variables columns and rows and bind them to Tab in Main's initialize.

APP.java

public class App extends Application {

    private static Scene scene;
    public static Connection conn;
    @Override
    public void start(Stage stage) throws IOException {
        try{
        conn=java.sql.DriverManager.getConnection("jdbc:sqlite:sample.db");
        if(conn!=null){
            conn.createStatement().execute("CREATE TABLE IF NOT EXISTS tab1(Field0 TEXT, Field1 TEXT, Field2 TEXT);");
            conn.createStatement().execute("CREATE TABLE IF NOT EXISTS tab2(Field3 TEXT, Field4 TEXT);");
        }
        }catch(Exception ex){
            System.out.println(ex);
        }
        scene = new Scene(loadFXML("main"), 640, 480);
        stage.setScene(scene);
        stage.show();
    }
    private static Parent loadFXML(String fxml) throws IOException {
        FXMLLoader fxmlLoader = new FXMLLoader(App.class.getResource(fxml + ".fxml"));
        return fxmlLoader.load();
    }

    public static void main(String[] args) {
        launch();
    }
    public static ResultSet getRS(String table){
        String sql="SELECT * FROM "+table;
        ResultSet rs=null;
        try{
            rs=conn.createStatement().executeQuery(sql);
        }catch(Exception ex){
            System.out.println(ex);
        }
        return rs;
    }
}

MAIN.FXML

<?xml version="1.0" encoding="UTF-8"?>

<?import javafx.scene.control.Menu?>
<?import javafx.scene.control.MenuBar?>
<?import javafx.scene.control.MenuItem?>
<?import javafx.scene.control.TableView?>
<?import javafx.scene.layout.VBox?>

<VBox xmlns="http://javafx.com/javafx/19" xmlns:fx="http://javafx.com/fxml/1" fx:controller="nic.testfx.Main">
   <children>
      <MenuBar>
        <menus>
          <Menu mnemonicParsing="false" text="File">
            <items>
              <MenuItem mnemonicParsing="false" onAction="#loadRem" text="Load Remaining" />
            </items>
          </Menu>
        </menus>
      </MenuBar>
      <TableView fx:id="Tab" prefHeight="200.0" prefWidth="200.0" />
      <VBox fx:id="remPane" prefHeight="200.0" prefWidth="100.0" />
   </children>
</VBox>

MAIN.JAVA

public class Main implements Initializable {
    @FXML
    public TableView<ObservableList<String>> Tab;
    @FXML
    private VBox remPane;
    
    @Override
    public void initialize(URL url, ResourceBundle rb) {
        Tab.itemsProperty().bind(getTabRow());
    }
public void makeTable(ResultSet rs){
    try{
        var rsm=rs.getMetaData();
        ObservableList<TableColumn<ObservableList<String>,String>>cols=FXCollections.observableArrayList();
        for(int i=0;i<rsm.getColumnCount();i++){
            final int j=i;
            TableColumn<ObservableList<String>,String> col=new TableColumn(rsm.getColumnName(i+1));
            col.setCellValueFactory(param->new SimpleStringProperty(param.getValue().get(j)));
            cols.add(col);
        }
        ObservableList<ObservableList<String>> arows=FXCollections.observableArrayList();
        while(rs.next()){
            ObservableList<String> row=FXCollections.observableArrayList();
            for(int i=1;i<=rsm.getColumnCount();i++){
                row.add(rs.getString(i));
            }
            arows.add(row);
        }
        setTable(cols,arows);
    }catch(Exception ex){
        System.out.println(ex);
    }
}
    private static final ObservableList<TableColumn<ObservableList<String>,String>> columns=FXCollections.observableArrayList();
    private static final javafx.beans.property.ListProperty<ObservableList<String>> rows=new javafx.beans.property.SimpleListProperty();
    private javafx.beans.property.ListProperty getTabRow(){
        Tab.getColumns().clear();
        Tab.getColumns().addAll(columns);
        return rows;
    }
    private static void setTable(ObservableList<TableColumn<ObservableList<String>,String>>c,ObservableList<ObservableList<String>> r){
        columns.setAll(c);
        rows.set(r);
    }

    @FXML
    private void loadRem(ActionEvent event) {
        try{
            for(int i=remPane.getChildren().size()-1;i>=0;i--){
                    remPane.getChildren().remove(i);
                }
                javafx.fxml.FXMLLoader fxmlLoader=new javafx.fxml.FXMLLoader();
                fxmlLoader.setLocation(getClass().getResource("rem.fxml"));
                javafx.scene.layout.Pane panel=fxmlLoader.load();
                remPane.getChildren().add(panel);
                makeTable(App.getRS("tab1"));
        }catch(Exception ex){
            System.out.println(ex);
        }
    }
}

REM.FXML

<?xml version="1.0" encoding="UTF-8"?>

<?import javafx.scene.control.Button?>
<?import javafx.scene.layout.VBox?>

<VBox alignment="CENTER" xmlns="http://javafx.com/javafx/19" xmlns:fx="http://javafx.com/fxml/1" fx:controller="nic.testfx.Rem">
   <children>
      <Button fx:id="btn" mnemonicParsing="false" onAction="#loadTab" text="Button" />
   </children>
</VBox>

REM.JAVA

public class Rem implements Initializable {

    @FXML
    private Button btn;
    @Override
    public void initialize(URL url, ResourceBundle rb) {
        // TODO
    }    
    @FXML
    private void loadTab(ActionEvent event) {
        try{
            var fxml=new javafx.fxml.FXMLLoader(App.class.getResource("main.fxml"));
            fxml.load();
            Main controller=fxml.getController();
            var rs=App.getRS("tab2");
            controller.makeTable(rs);
        }catch(Exception ex){
            System.out.println(ex);
        }
    }
}

Answer 1

OK I got it. Created a java class which encapsulate method makeTable:

MODEL.JAVA

public class Model{
    private final TableView table;
    public Model(TableView t){
        this.table=t;
    }
    public void makeTable(ResultSet rs){
        ObservableList<TableColumn<ObservableList<String>,String>>tabcols=FXCollections.observableArrayList();
        ObservableList<ObservableList<String>>tabrows=FXCollections.observableArrayList();
        //Create TableColumns and add to tabcols;
        while(rs.next()){
            //Create ObservableList<String>, get data from rs, and add to tabrows
        }
        this.table.getColumns().setAll(tabcols);
        this.table.getItems().setAll(tabrows);
    }
}

Next, in Controller file Main.java created a static instance of Model:

MAIN.JAVA

public class Main implements Initializable{
    @FXML
    private TableView<ObservableList<String>> Tab;
    static Model model;
    @Override
    public void initialize (URL url, ResourceBundle rb){
        model=new Model(Tab);
    }
}

Now I can use model from Rem controller:

REM.JAVA

public class Rem implements Initializable{
    @FXML
    private Button btn;
    @Override
    public void initialize (URL url, ResourceBundle rb){
       //TODO
    }
    @FXML
    private void loadTab(ActionEvent event){
        var rs=App.getRS("tab2");
        Main.model.makeTable(rs);
}