How to load same main fxml file multiple times by clicking on the new tab button?

[San Aadit]

I am not able to add new tab functionality to browser.I already search a lot on google but nothing work.I want to load main fxml file again nad again dynamically by clicking on new tab button.

Below is Main.java file

package tabcheck;
import javafx.application.Application;
//all imports..

public class Main extends Application{
 
public static void main(String[] args){
    launch(args);
}
@Override
public void start(Stage primaryStage) throws Exception {
   try{
       Parent root = FXMLLoader.load(getClass().getResource("/tabcheck/First page.fxml"));
       Scene scene = new Scene(root);
       scene.getStylesheets().add("tabcheck/application.css");
       primaryStage.setScene(scene);
       primaryStage.show();
      } 
      catch(Exception e){
       e.printStackTrace();}
   }
}

Here is some part of First-page.fxml file which is the main view...

<?xml version="1.0" encoding="UTF-8"?>
<?import javafx.scene.*?>
<?import javafx.scene.input.*?>
<!-- all imports -->

<AnchorPane xmlns="http://javafx.com/javafx/8.0.40" xmlns:fx="http://javafx.com/fxml/1" fx:controller="tabcheck.Home_controller">
   <children>
      <TabPane fx:id="tabpane" prefHeight="629.0" prefWidth="1024.0" AnchorPane.bottomAnchor="0.0" AnchorPane.leftAnchor="0.0" AnchorPane.rightAnchor="0.0" AnchorPane.topAnchor="0.0">
         <tabs>
            <Tab fx:id="tab1" text="Tab1">
               <content>
                  <AnchorPane>
                     <children>
                        <BorderPane fx:id="mainLayout" prefHeight="600.0" prefWidth="1024.0">
                           <top>
                              <HBox fx:id="Hbox" prefHeight="54.0" prefWidth="1024.0" spacing="15.0" BorderPane.alignment="CENTER">
                                 <children>
                                  <Button fx:id="go_btn" mnemonicParsing="false" onAction="#G" prefHeight="25.0" prefWidth="30.0"/>
                                  <Button fx:id="smartnote_btn" layoutX="419.0" layoutY="10.0" mnemonicParsing="false" onAction="#OpenNotes" prefHeight="25.0" prefWidth="30.0"/>
                                  <Button fx:id="newtab_btn" layoutX="523.0" layoutY="10.0" mnemonicParsing="false" onAction="#addTab" prefHeight="25.0" prefWidth="30.0"/>
                                 <MenuButton fx:id="setting_btn" mnemonicParsing="false" prefHeight="25.0" prefWidth="50.0">
                                   <items>
                                   <MenuItem mnemonicParsing="false" text="Bookmark" />
                                   </items>
                                    </MenuButton>
                                 </children>
                                </HBox>
                           </top>
                           <center>
                              <WebView fx:id="webView" prefHeight="200.0" prefWidth="200.0" BorderPane.alignment="CENTER" />
                          </center>
                        </BorderPane>
                     </children>
                  </AnchorPane>
               </content>
            </Tab>
         </tabs>
      </TabPane>
   </children>
</AnchorPane>

Below is controller of First-page.fxml

Home_controller.java

package tabcheck;
import java.io.IOException;
import java.net.URL;
//All imports...

public class Home_controller implements Initializable{
    @FXML private Button forward_btn;
    @FXML private Button refresh_btn;
    @FXML private Button go_btn;
    @FXML private TextField addressField;
    @FXML private WebView webView;
    @FXML private TabPane tabpane ;
    @FXML private BorderPane mainLayout;
    private Main main;
    private WebEngine webEngine;
      
     @Override
      public void initialize(URL url, ResourceBundle rb){
          webEngine = webView.getEngine();
          webEngine.load("http://www.google.com");
        
        }

     @FXML
     private void addTab() throws IOException{
         Tab tab = new Tab("New Tab");
         tabpane.getTabs().add(tab);
        // tabpane.getSelectionModel().clearSelection();
         FXMLLoader loader = new FXMLLoader();
         loader.setLocation(Main.class.getResource("/tabcheck/Tab-First-page.fxml"));
         AnchorPane tabAnchor = loader.load();
         tab.setContent(tabAnchor);
      }
}

In Controller class Tab-First-page.fxml is the copy of first-page.fxml and changes in Tab-first-page.fxml is that it does not contain Tabpane otherwise it is same as First-page.fxml
I am able to load multiple tab from First-page.fxml but not able to open new tab from Tab-first-page.fxml that is, From main page multiple tabs can be open dynamically but from those open tabs I am not able to open new tabs. Following is the error I am getting...

Exception in thread "JavaFX Application Thread" java.lang.RuntimeException: java.lang.reflect.InvocationTargetException
//Lot more error...
**Caused by: java.lang.NullPointerException
at tabcheck.Home_controller.addTab(Home_controller.java:200)
... 62 more**
Home_controller.java:200 is tabpane.getTabs().add(tab); in addTab() method. I have tried every possible solution but not working,please any one can help?

I have also try to do it by adding listener in addTab() but still null pointer exception is coming...also search on other websites but nothing is working...please anybody can help??