UI 打印空值而不是 txt 文件中的文本

Question

(Edited) Trying to make a shopping cart that when I click on a book, it takes the book title from the text file and then takes the value and adds or deletes it to the total.

At the current moment, I do not have all the code, just working on pulling the text information in from the text file. and when I currently start up the program it prints out "Null" value to the screen instead of the book titles

Original Working file

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();

    }
}

Inside the BookPrices file

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

Answer 1

order of operations mistake.

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

    @Override
    public void start(Stage primaryStage) throws FileNotFoundException
    {

            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++;    
        }

    //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);
    });