UI打印Null值，而不是txt文件中的文本

（已编辑）尝试制作一个购物车，当我单击一本书时，它会从文本文件中获取书名，然后获取值并将其添加或删除到总计中。

目前，我还没有所有代码，只是要从文本文件中提取文本信息。当我当前启动程序时，它将“ Null”值打印到屏幕上，而不是书名

原始工作文件

package shoppingcart2;
import java.awt.BorderLayout;
import java.awt.Font;
import java.io.File;
import java.io.FileNotFoundException;
import java.util.*;
import javafx.application.Application;
import static javafx.application.Application.launch;
import javafx.event.ActionEvent;
import javafx.event.EventHandler;
import javafx.stage.Stage;
import javafx.scene.Scene;
import javafx.scene.control.Button;
import javafx.scene.control.Label;
import javafx.scene.control.TextField;
import javafx.scene.control.ListView;
import javafx.scene.control.ComboBox;
import javafx.scene.layout.VBox;
import javafx.scene.layout.HBox;
import javafx.scene.layout.StackPane;
import javafx.scene.layout.GridPane;
import javafx.scene.transform.Scale;
import javafx.scene.image.Image;
import javafx.scene.image.ImageView;
import javafx.geometry.Pos;
import javafx.geometry.Insets;
import javax.swing.BorderFactory;
import javax.swing.JButton;
import javax.swing.JLabel;
import javax.swing.JList;
import javax.swing.JPanel;


public class ShoppingCart2 extends Application
{
    private JPanel listPanel;
    private JPanel shoppingPanel;
    private JPanel buttonsPanel;
    private JList listItems;

    private JButton addButton;
    private JButton removeButton;
    private JButton clearButton;
    private JButton checkoutButton;

    private String[] listArray = new String[7];
    private java.awt.List cartItems = new java.awt.List();

    private final double salesTax = 0.06;

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

    @Override
    public void start(Stage primaryStage) throws FileNotFoundException
    {
    //list view items book
    ListView<String> listView = new ListView<>();
    listView.setPrefSize(200, 170);
    listView.getItems().addAll(listArray);
    // create label to display the selection
    Label selectedNameLabel = new Label("Select a Book");
    //Button for selection
    Button getButton = new Button("Add to Cart");
    //Event for Add to cart button
    getButton.setOnAction(event ->
    {
        //Get book
        String selected = listView.getSelectionModel().getSelectedItem();
        //Display selected item in label
        selectedNameLabel.setText(selected);
    });

    String line;
        int index = 0;

        File file = new File("BookPrices.txt");
        Scanner fileReader = new Scanner(file);

        while(fileReader.hasNext())
        {
            line = fileReader.nextLine();
            String [] titles = line.split(",");
            listArray[index] = titles[0];
            index++;    
        }

    //Controls to VBox
    VBox vbox = new VBox(10, listView, selectedNameLabel, getButton);
    vbox.setPadding(new Insets(10));
    vbox.setAlignment(Pos.CENTER);

    //Show
    Scene scene = new Scene(vbox);
    primaryStage.setScene(scene);
    primaryStage.show();

    }
}

在BookPrices文件中

I Did It Your Way, 11.95
The History of Scotland, 14.50
Learn Calculus in One Day, 29.95
Feel the Stress, 18.50
Great Poems, 12.95
Europe on a Shoestring, 10.95
The Life of Mozart, 14.50

问题来源：Stack Overflow