Javafx FXML loader getcontroller returns null - javafx

Question

In my program i have a tabPane with each tab having in own FXML file and controller .I have loaded the FXML file for tab 2 (Schedular).I`m trying to call a function in my child controller (Scheduler) from my parent controller(FXML Document) . When i load the controller using FXML Loader it returns a null. How can i solve this .
Here is my main code:
Main FXMLDocument :
<AnchorPane xmlns:fx="http://javafx.com/fxml/1" fx:id="AnchorPane" prefHeight="600" prefWidth="800" xmlns="http://javafx.com/javafx/8.0.65" fx:controller="showprojavafxml.FXMLDocumentController">
<children>

Answer 1

The FXMLLoader only instantiates the controller when it loads the fxml file (this has to be the case, since the controller class is specified in the fxml file...). Since you never call load() on the loader, the controller is never created.
It looks like you are referencing the FXML file twice through two different mechanisms: once in FXMLDocumentController.initialize(), where you create a FXMLLoader whose location is set to the fxml file, and once in the main FXML document itself, via a <fx:include>. The <fx:include> is causing the UI defined in Scheduler.fxml to be displayed; the FXMLLoader you create in the initialize() method is not (because you never call load() and display the result).
To reference a controller for an included fxml, use the "Nested controller" technique.
First, add an fx:id to your fx:include:
<Tab fx:id="tab2" text="Scheduler" >
<fx:include fx:id="scheduler" source="Scheduler.fxml" />
</Tab>
Now you can inject the controller into a field whose name is the fx:id with the text "Controller" appended:
public class FXMLDocumentController {
#FXML
private SchedulerController schedulerController ;
#Override
public void initialize(URL url, ResourceBundle rb) {
schedulerController.refreshList();
}
}