java - 尝试使用按钮更改 JTextFields

Question

我试图在点击下一个按钮后获取要在 JTextFields 中显示的下一组值。我是编程新手，所以我不太确定我错过了什么。我想要发生的是，当我点击下一个按钮时，当窗口显示下一组值时，下一组值现在将显示在适当的 JTextFields 中，不幸的是，最终发生的是什么都没有。我尝试了几种不同的方法来让它发挥作用，但到目前为止还没有任何效果。我知道这不是按钮本身，因为如果我更改旁边的 actionPerformed 为 setTitle(“5000”)，它将更改窗口内的标题。如有任何帮助，我们将不胜感激。

import java.awt.FlowLayout;
import java.awt.GridLayout;
import java.awt.event.*;
import java.util.Arrays;
import javax.swing.*;
import java.awt.*;



public class GUI extends JFrame implements ActionListener {
    JButton next;
    JButton previous;
    JButton first;
    JButton last;

    private JLabel itmNum = new JLabel("Item Number: ", SwingConstants.RIGHT);
    private JTextField itemNumber;
    private JLabel proNm = new JLabel ("Product Name: ", SwingConstants.RIGHT);
    private JTextField prodName;
    private JLabel yr = new JLabel("Year Made: ", SwingConstants.RIGHT);
    private JTextField year;
    private JLabel unNum = new JLabel("Unit Number: ", SwingConstants.RIGHT);
    private JTextField unitNumber;
    private JLabel prodPrice = new JLabel("Product Price: ", SwingConstants.RIGHT);
    private JTextField price;
    private JLabel restkFee = new JLabel("Restocking Fee", SwingConstants.RIGHT);
    private JTextField rsFee;
    private JLabel prodInValue = new JLabel("Product Inventory Value",   SwingConstants.RIGHT);
    private JTextField prodValue;
    private JLabel totalValue = new JLabel("Total Value of All Products", SwingConstants.RIGHT);
    private JTextField tValue;
    private double toValue;

    int nb = 0;
    char x = 'y';
    public GUI() 
    {

        super ("Inventory Program Part 5");
        setSize(800,800);
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        setLookAndFeel();




        first = new JButton("First");
        previous = new JButton("Previous");
        next = new JButton("Next");
        last = new JButton("Last");
        first.addActionListener(this);
        previous.addActionListener(this);
        next.addActionListener(this);
        last.addActionListener(this);




        Movies[] titles = new Movies[9];

        titles [0] = new Movies(10001, "King Arthur", 25 , 9.99, 2004, .05);

        titles [1] = new Movies(10002,"Tron", 25, 7.99, 1982, .05);

        titles [2] = new Movies(10003, "Tron: Legacy",25,24.99,2010,.05);

        titles [3] = new Movies(10004,"Braveheart", 25,2.50,1995,.05);

        titles [4] = new Movies(10005,"Gladiator",25,2.50,2000,.05);

        titles [5] = new Movies(10006,"CaddyShack SE",25,19.99,1980,.05);

        titles [6] = new Movies (10007,"Hackers",25,12.50,1995,.05);

        titles [7] = new Movies (10008,"Die Hard Trilogy",25,19.99,1988,.05);

        titles [8] = new Movies (10009,"Terminator",25,4.99,1984,.05);

        Arrays.sort (titles, DVD.prodNameComparator);






                        itemNumber.setText(Double.toString(titles[nb].getitemNum()));
                        prodName.setText(titles[nb].getprodName());
                        year.setText(Integer.toString(titles[nb].getYear()));
                        unitNumber.setText(Integer.toString(titles[nb].getunitNum()));
                        price.setText(Float.toString(titles[nb].getprice()));
                        rsFee.setText(Double.toString(titles[nb].getRestkFee()));
                        prodValue.setText(Double.toString(titles[nb].getprodValue()));
                        tValue.setText("2636");





        setLayout(new GridLayout(8,4));
        add(itmNum);
        add(itemNumber);
        add(proNm);
        add(prodName);
        add(yr);
        add(year);
        add(unNum);
        add(unitNumber);
        add(prodPrice);
        add(price);
        add(restkFee);
        add(rsFee);
        add(prodInValue);
        add(prodValue);
        add(totalValue);
        add(tValue);
        add(first);
        add(previous);
        add(next);
        add(last);
        setLookAndFeel();
        setVisible(true);


    }



    public void updateFields()
    {
        itemNumber.getText();
        prodName.getText();
        year.getText();
        unitNumber.getText();
        price.getText();
        rsFee.getText();
        prodValue.getText();
        tValue.getText();
    }




    public void actionPerformed(ActionEvent evt){
        Object source = evt.getSource();
        if (source == next) 
        {
            nb++;

        }

    }

    private void setLookAndFeel()
    {
        try{
            UIManager.setLookAndFeel("com.sun.java.swing.plaf.nimbus.NimbusLookAndFeel");
                        SwingUtilities.updateComponentTreeUI(this);
            } catch (Exception e) {
                System.err.println("couln't use the system"+ "look and feel: " + e);
            }

    }


    }

Answer 1

您的ActionListener只有一项分配

nb = 1;

和重绘。这不会使用 Movies 数组 titles 中的值更新 JTextFields。您需要明确地执行此操作。

itemNumber.setText(Double.toString(titles[nb].getItemNum()));
...

为了实现这一点，您需要将您的 Movies titles 数组设置为类成员变量，以便可以从 ActionListener 访问它>.

此外，您实际上从未更改 ActionListener 中 nb 的值。由于它是“下一步”按钮，您可能需要增加它:

nb++;

旁注:

• Java 使用camelcase，这将使方法 getitemNum getItemNum。
• ArrayList 可以让您更灵活地在固定大小的数组上添加电影标题。