pane.getChildren().addAll(); not working in a scene javafx - javafx

Question

This code will not allow the line to draw in my window... All I have in the fxml file is a simple pane with the fx:id of hi to test things out. There is no error, the line simply doesn't appear. I've also tried this with a box and circle. I really need help, this is an important project.
import java.net.URL;
import java.util.ResourceBundle;
import javafx.fxml.FXML;
import javafx.fxml.Initializable;
import javafx.scene.layout.AnchorPane;
import javafx.scene.layout.BorderPane;
import javafx.scene.layout.Pane;
import javafx.scene.shape.Line;
import javafx.scene.Scene;
import javafx.scene.paint.Color;
public class PlotSceneController implements Initializable {
#FXML
Pane hi;
#Override
public void initialize(URL url, ResourceBundle rb) {
Line line = new Line(0,0,10,110);
line.setStroke(Color.BLACK);
line.setStrokeWidth(10);
hi.getChildren().addAll(line);
}
}
FXML File
<?xml version="1.0" encoding="UTF-8"?>
<?import javafx.scene.shape.*?>
<?import java.lang.*?>
<?import java.net.*?>
<?import java.util.*?>
<?import javafx.scene.*?>
<?import javafx.scene.control.*?>
<?import javafx.scene.layout.*?>
<Pane fx:id="hi" maxHeight="-Infinity" maxWidth="-Infinity" minHeight="-
Infinity" minWidth="-Infinity" prefHeight="400.0" prefWidth="600.0"
xmlns="http://javafx.com/javafx/8" xmlns:fx="http://javafx.com/fxml/1">
<children>
</children>
</Pane>
Main Class, leads to another page with a button that leads to the page I'm having trouble with.
public class Main extends Application {
Stage firstStage;
Scene loginButton;
#Override
public void start(Stage primaryStage) throws Exception {
Parent root = FXMLLoader.load(getClass().getResource("Main.fxml"));
firstStage = primaryStage;
loginButton = new Scene(root, 900, 700);
primaryStage.setTitle("Treatment Data");
primaryStage.setScene(loginButton);
primaryStage.show();
}
/**
* #param args the command line arguments
*/
public static void main(String[] args) { //Main class
launch(args); //Launches application/window
}
}

Answer 1

You are missed to set a controller class PlotSceneController.java. Set controller class in different two way like using main class setController() method or set controller class in left bottom side controller pane in scene Builder screen.
Using Main
FXMLLoader loader = new FXMLLoader(getClass().getResource("Main.fxml"));
loader.setController(new PlotSceneController());
Parent root = (Parent) loader.load();
Or Using FXML
Set Controller class with full package path like below way