fx:id="grid" stays null in controller - javafx

Question

grid stays null when user clicks the button that calls 'pressLookUp' User is suppose to go from an old stage to the new one in the fxml file. And before the new window is shown, I want to add in values to the grids children from the database using grid.add(node, colIndex, rowIndex)
Controller:
package login;
import javafx.event.ActionEvent;
import javafx.fxml.FXML;
import javafx.fxml.FXMLLoader;
import javafx.scene.Node;
import javafx.scene.Parent;
import javafx.scene.Scene;
import javafx.scene.control.Label;
import javafx.scene.control.TextArea;
import javafx.scene.layout.GridPane;
import javafx.stage.Stage;
import userGroups.User;
import java.io.BufferedReader;
import java.io.FileReader;
import java.io.IOException;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.Statement;
public class studentOptionsController{
#FXML
private GridPane grid;//gridpane from ClassesToAdd
public void pressLookUp(ActionEvent event) throws IOException{
Parent userOption = FXMLLoader.load(getClass().getResource("ClassesToAdd.fxml"));
Scene classesToAddScene = new Scene(userOption);
Stage app_stage = (Stage) ((Node) event.getSource()).getScene().getWindow();
app_stage.setScene(classesToAddScene);
app_stage.show();
Connection c = null;
Statement stmt = null;
try{
c = DriverManager.getConnection("jdbc:sqlite:users.db");
c.setAutoCommit(false);
System.out.println("Opened database successfully");
stmt = c.createStatement();
ResultSet rs = stmt.executeQuery("SELECT * FROM Classes WHERE IDCLASSES= " + "5;");
int currentIndex = 0;
int currentRow = 0;
//assusming all columns are NOT NULL
while(rs.next()){
Label currentLabel = new Label();
currentLabel.setText(rs.getString("CLASSNAME"));
System.out.println(currentLabel.getText());
grid.add(currentLabel, 5, 0 );
/*if (rs.getString("SUSERNAME") != null && rs.getString("STUDENTPASS") != null){
String username = rs.getString("SUSERNAME");
System.out.println( "SUSERNAME = " + username );
String password = rs.getString("STUDENTPASS");
System.out.println("STUDENTPASS = " + password);
}*/
}
rs.close();
stmt.close();
c.close();
} catch ( Exception e ){
System.err.println( e.getClass().getName() + ": " + e.getMessage() );
//System.exit(0);
}
System.out.println("Operation done successfully");
}
}
FXML:
<?xml version="1.0" encoding="UTF-8"?>
<?import javafx.scene.control.Button?>
<?import javafx.scene.control.Label?>
<?import javafx.scene.layout.ColumnConstraints?>
<?import javafx.scene.layout.GridPane?>
<?import javafx.scene.layout.RowConstraints?>
<GridPane fx:id="grid" prefHeight="400.0" prefWidth="850"
xmlns="http://javafx.com/javafx/8.0.121" xmlns:fx="http://javafx.com/fxml/1"
fx:controller="login.studentOptionsController">
<columnConstraints>
<ColumnConstraints percentWidth="11" />
<ColumnConstraints percentWidth="11" />
<ColumnConstraints percentWidth="11" />
<ColumnConstraints percentWidth="11" />
<ColumnConstraints percentWidth="11" />
<ColumnConstraints percentWidth="11" />
<ColumnConstraints percentWidth="11" />
<ColumnConstraints percentWidth="11" />
<ColumnConstraints percentWidth="12" /> <!-- This column for 'Add
Class' buttons ?-->
</columnConstraints>
<rowConstraints>
<RowConstraints />
</rowConstraints>
<children>
<Label maxHeight="Infinity" maxWidth="Infinity" style=" -fx-border-color:gray; " text="Class Name" GridPane.columnIndex="0" GridPane.rowIndex="0" />
<Label maxHeight="Infinity" maxWidth="Infinity" style=" -fx-border-color:gray; " text="Size of Class" GridPane.columnIndex="1" GridPane.rowIndex="0" />
<Label maxHeight="Infinity" maxWidth="Infinity" style=" -fx-border-color:gray; " text="Spots Taken" GridPane.columnIndex="2" GridPane.rowIndex="0" />
<Label maxHeight="Infinity" maxWidth="Infinity" style=" -fx-border-color:gray; " text="Instructor" GridPane.columnIndex="3" GridPane.rowIndex="0" />
<Label maxHeight="Infinity" maxWidth="Infinity" style=" -fx-border-color:gray; " text="CRN" GridPane.columnIndex="4" GridPane.rowIndex="0" />
<Label maxHeight="Infinity" maxWidth="Infinity" style=" -fx-border-color:gray; " text="Days" GridPane.columnIndex="5" GridPane.rowIndex="0" />
<Label maxHeight="Infinity" maxWidth="Infinity" style=" -fx-border-color:gray; " text="Time" GridPane.columnIndex="6" GridPane.rowIndex="0" />
<Label maxHeight="Infinity" maxWidth="Infinity" style=" -fx-border-color:gray; " text="Subject" GridPane.columnIndex="7" GridPane.rowIndex="0" />
<Button maxHeight="Infinity" maxWidth="Infinity" mnemonicParsing="false" onAction="#pressBack" style=" -fx-background-color:red; -fx-border-color:black" text="Back..." GridPane.columnIndex="8" GridPane.rowIndex="0" />
</children>
</GridPane>
Output on system:
Opened database successfully
java.lang.NullPointerException: null
Operation done successfully

Answer 1

No clue why this works but it does.
public void pressLookUp(ActionEvent event) throws IOException{
FXMLLoader loader = new FXMLLoader(getClass().getResource("ClassesToAdd.fxml"));
Parent userOption = loader.load();
grid = loader.getRoot();
Scene classesToAddScene = new Scene(userOption);
Stage app_stage = (Stage) ((Node) event.getSource()).getScene().getWindow();
app_stage.setScene(classesToAddScene);
app_stage.show();
Connection c = null;
Statement stmt = null;
try{
c = DriverManager.getConnection("jdbc:sqlite:users.db");
c.setAutoCommit(false);
System.out.println("Opened database successfully");
stmt = c.createStatement();
ResultSet rs = stmt.executeQuery("SELECT * FROM Classes WHERE IDCLASSES= " + "5;");
int currentIndex = 0;
int currentRow = 0;
//assusming all columns are NOT NULL
while(rs.next()){
Label currentLabel = new Label();
currentLabel.setText(rs.getString("CLASSNAME"));
System.out.println(currentLabel.getText());
grid.add(currentLabel, 0, 1 );
}
loader.setRoot(grid);
rs.close();
stmt.close();
c.close();
} catch ( Exception e ){
System.err.println( e.getClass().getName() + ": " + e.getMessage() );
System.exit(0);
}
System.out.println("Operation done successfully");
}