How to get UserInput from javaFX Text field:

Question

Currently, I am working on an application that includes a UI with a simple login verification system. When I attempt to grab input from the userInput textfield from the StoreUser() method in the controller, I get an error:

Caused by: java.lang.NullPointerException
at com.company.Controller.storePassword(Controller.java:32)
at com.company.Controller.handleButtonAction(Controller.java:49)
... 58 more

These are the classes in question:

Main class:

package com.company;

import javafx.application.Application;
import javafx.application.Platform;
import javafx.fxml.FXMLLoader;
import javafx.scene.Parent;
import javafx.scene.Scene;
import javafx.stage.Screen;
import javafx.stage.Stage;

import javax.swing.*;
import java.awt.*;
import java.io.File;
import java.io.IOException;
import java.security.NoSuchAlgorithmException;
import java.security.spec.InvalidKeySpecException;
import java.sql.SQLException;

public class Main extends Application {

    int ScreenWidth = (int) Screen.getPrimary().getBounds().getWidth();
    int ScreenHeight = (int) Screen.getPrimary().getBounds().getHeight();

    //Verifies that the program has been run before on the computer. Allows for initial logins, first user account creation, etc.
public static void initialLoginVerify() throws IOException {
    File f = new File("C:\\453-Project");
    boolean path_check = f.exists();
    if (!path_check) {
        f.mkdir();
    }
}

@Override
public void start(Stage primaryStage) throws Exception {
    Parent loginPageParent = FXMLLoader.load(getClass().getResource("loginPage.fxml"));
    primaryStage.setTitle("Harmony v0.11");
    primaryStage.setScene(new Scene(loginPageParent, ScreenWidth, ScreenHeight - 60));
    primaryStage.setMaximized(true);
    primaryStage.show();

}

//this is where the bulk of the program can start. It allows nothing else about the program to be accessed without
//successfully logging in first
public static void After_Login(){
    System.out.println("You logged in successfully :D");
}

public static void main(String[] args) throws IOException {

    //test username is john, test password is Doe
    launch(args);
}

}

Controller class:

package com.company;

import javafx.event.ActionEvent;
import javafx.fxml.FXML;
import javafx.fxml.FXMLLoader;
import javafx.fxml.Initializable;
import javafx.scene.Node;
import javafx.scene.Parent;
import javafx.scene.Scene;
import javafx.scene.control.Button;
import javafx.scene.control.PasswordField;
import javafx.scene.control.TextField;
import javafx.stage.Screen;
import javafx.stage.Stage;

import java.io.IOException;
import java.net.URL;
import java.security.NoSuchAlgorithmException;
import java.security.spec.InvalidKeySpecException;
import java.sql.SQLException;
import java.util.ResourceBundle;

public class Controller implements Initializable {
    @FXML static TextField userInput;
    @FXML static PasswordField passwordInput;
    @FXML Button logButton;
    int ScreenWidth = (int) Screen.getPrimary().getBounds().getWidth();
    int ScreenHeight = (int) Screen.getPrimary().getBounds().getHeight();

public static String storePassword() {
    System.out.println("inside of storepassword");
    String passWord = passwordInput.getText();
    return passWord;

}

public static String storeUser() {
    System.out.println("inside of storeuser");
    String userName = userInput.getText();
    System.out.println("Username: " + userName + "\n");
    return userName;
}




@FXML
public void handleButtonAction (ActionEvent event) throws IOException, InvalidKeySpecException, NoSuchAlgorithmException {
    storePassword();
    storeUser();
    Parent mainPageParent = FXMLLoader.load(getClass().getResource("mainPage.fxml"));
    Stage app_stage = (Stage) ((Node) event.getSource()).getScene().getWindow();
    app_stage.setScene(new Scene(mainPageParent,ScreenWidth,ScreenHeight-60));
    app_stage.setMaximized(true);
    app_stage.show();


}

@FXML
private void handleLogoutButton (ActionEvent event) throws IOException {
    Parent loginPageParent = FXMLLoader.load(getClass().getResource("loginPage.fxml"));
    Stage app_Stage2 = (Stage) ((Node) event.getSource()).getScene().getWindow();
    app_Stage2.setScene(new Scene(loginPageParent, ScreenWidth, ScreenHeight-60));
    app_Stage2.setMaximized(true);
    app_Stage2.show();
}
@FXML
private void creationAccountButton (ActionEvent event) throws IOException {
    Parent creationPageParent = FXMLLoader.load(getClass().getResource("accountCreation.fxml"));
    Stage app_Stage3 = (Stage) ((Node) event.getSource()).getScene().getWindow();
    app_Stage3.setScene(new Scene(creationPageParent, ScreenWidth, ScreenHeight-60));
    app_Stage3.setMaximized(true);
    app_Stage3.show();
}



@Override
public void initialize(URL url, ResourceBundle resourceBundle) {}

Any help would be greaty appreciated! Thank you so much!