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

<?import java.lang.*?>
<?import java.util.*?>
<?import javafx.scene.*?>
<?import javafx.scene.control.*?>
<?import javafx.scene.layout.*?>

<AnchorPane maxHeight="-Infinity" maxWidth="-Infinity" minHeight="-Infinity" minWidth="-Infinity" prefHeight="480.0" prefWidth="320.0" xmlns="http://javafx.com/javafx/8" xmlns:fx="http://javafx.com/fxml/1" fx:controller="Test">
   <children>
      <Button id="btnbuy" fx:id="btnbuy" layoutX="134.0" layoutY="2.0" mnemonicParsing="false" onAction="#loadSecondFxml" text="Purchase" />
      <Button id="btnSell" fx:id="btnsell" layoutX="140.0" layoutY="454.0" mnemonicParsing="false" text="Sell" />
   </children>
</AnchorPane>

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

<?import java.lang.*?>
<?import java.util.*?>
<?import javafx.scene.*?>
<?import javafx.scene.control.*?>
<?import javafx.scene.layout.*?>

<AnchorPane maxHeight="-Infinity" maxWidth="-Infinity" minHeight="-Infinity" minWidth="-Infinity" prefHeight="480.0" prefWidth="320.0" xmlns="http://javafx.com/javafx/8" xmlns:fx="http://javafx.com/fxml/1" fx:controller="Test">
   <children>
      <Pane layoutX="6.0" maxHeight="-Infinity" maxWidth="-Infinity" minHeight="-Infinity" minWidth="-Infinity" prefHeight="480.0" prefWidth="320.0">
         <children>
            <Label layoutX="146.0" layoutY="232.0" text="You got here" />
         </children></Pane>
   </children>
</AnchorPane>

import javafx.application.Application;
import javafx.fxml.FXMLLoader;
import javafx.scene.Parent;
import javafx.scene.Scene;
import javafx.scene.control.Button;
import javafx.stage.Stage;

public class Test extends Application {
    private MainPage parentForm;
    //private Panel panel;
    public Button btnbuy;
    public Button btnsell;

    public Test(){
    }
    public void start(Stage primaryStage) throws Exception{
        Parent root = FXMLLoader.load(getClass().getResource("Index.fxml"));
        primaryStage.setTitle("Hello World");
        primaryStage.setScene(new Scene(root, 320, 480));
        primaryStage.show();
    }
    public void loadSecondFxml() throws Exception{
        Stage primaryStage = new Stage();
        Parent root = FXMLLoader.load(getClass().getResource("MainPage.fxml"));
        primaryStage.setTitle("Hi");
        primaryStage.setScene(new Scene(root, 320, 480));
        primaryStage.show();
    }

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