Java / Blue j无法在组合框中选择除第1项以外的任何其他内容

Im using blue j for a project which is a java framework (not through my choice) I cant get it to print out what seat they have chosen because it always selects the 1st value A1.

我使用蓝色j作为一个java框架的项目（不是通过我的选择）我不能打印出他们选择的座位，因为它总是选择第一个值A1。

Its a seating plan that displays and image and a combo box in which you can select your seat for exmaple A1 and upon the button click save it prints out the seat you have chosen in a dialog box. Help!

它是一个显示和图像的座位计划和一个组合框，您可以在其中选择您的座位作为例子A1，点击按钮保存它打印出您在对话框中选择的座位。帮帮我！

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import javax.swing.event.*;
import javax.swing.border.*;
import java.lang.String;

import java.util.List;
import java.util.ArrayList;
import java.util.Iterator;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.io.*;
import javax.swing.JFrame;
import javax.swing.JOptionPane;


public class SeatingChart extends JFrame 

{
        private JLabel infoLabel;
        // Get the list of field names, used for ordering.
        String[] ordering =  
  {"A1","A2","A3","A4",                                                       
  "B1","B2","B3","B4",
  "C1","C2","C3","C4","D1","D2","D3","D4"};
        String chosenSeat;

        String ticket= "1" ;
  int ticketValue = Integer.parseInt(ticket);

/**
 * Main method for starting the system from a command line.
 */
public static void main(String[] args)
{
    SeatingChart gui = new SeatingChart();
}

/**
 * Create a visual aspect and display its GUI on screen.
 */
public SeatingChart()
{
    super("Choose Your seats");       
    makeFrame();
}

/**
 * Quit function: quit the application.
 */
private void quit()
{
    System.exit(0);
}

private void play()
{
    JFrame frames = new JFrame("Sample frame");
    frames.setSize(400, 400);
    frames.setVisible(false);
    frames.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    JOptionPane.showMessageDialog(frames, "You have chosen the seat " +chosenSeat);      
} 
/**
 * Create the complete application GUI.
 */
public void makeFrame ()
{
    // the following makes sure that our application exits when
    // the user closes its window
    setDefaultCloseOperation(EXIT_ON_CLOSE);

     JPanel contentPane = (JPanel) getContentPane();
    contentPane.setBorder(new EmptyBorder(6, 10, 10, 10));

       makeMenuBar(); //calls the menu bar method

       // Create the center with image
   JPanel centerPane = new JPanel();
    {
        centerPane.setLayout(new BorderLayout(8, 8));

        JLabel image = new JLabel(new ImageIcon("SeatingChart.jpg"));
        image.setSize (20,20);//dont work
        centerPane.add(image, BorderLayout.NORTH);
        centerPane.setBackground(Color.WHITE);

        infoLabel = new JLabel("Please use the chart to select where you would like to sit and save it. Do this for how many tickets you have");

       infoLabel.setHorizontalAlignment(SwingConstants.CENTER);
        centerPane.add(infoLabel, BorderLayout.CENTER);
    }
    contentPane.add(centerPane, BorderLayout.EAST);

       JPanel leftPane = new JPanel();
    {
        leftPane.setLayout(new BorderLayout(8, 8));

        // Set up components for ordering the list
        JPanel orderingPanel = new JPanel();
        orderingPanel.setLayout(new BorderLayout());
        orderingPanel.add(new JLabel("Choose your seat:"), BorderLayout.NORTH);

        // Create the combo box.
        JComboBox formatList = new JComboBox(ordering);
        orderingPanel.add(formatList, BorderLayout.CENTER);
        leftPane.add(orderingPanel, BorderLayout.NORTH);

        formatList.setSelectedIndex(0); 
        chosenSeat = formatList.getSelectedItem().toString();

        //formatList.removeItemAt(formatList.getSelectedIndex());          
    }

    contentPane.add(leftPane, BorderLayout.CENTER);
   JPanel toolbar = new JPanel();
    {
        toolbar.setLayout(new GridLayout(1, 0));

        JButton button = new JButton("Save");
        button.addActionListener(new ActionListener() {
                   public void actionPerformed(ActionEvent e) {
                       play();
                   }
               });
        toolbar.add(button);

        button = new JButton("Next");
        button.addActionListener(new ActionListener() {
                   public void actionPerformed(ActionEvent e) { 
                      // This button would allow the use to go to the next step
                   }
               });
        toolbar.add(button);

    }

    contentPane.add(toolbar, BorderLayout.SOUTH);

    // building is done - arrange the components      
    pack();

    // place this frame at the center of the screen and show
    Dimension d = Toolkit.getDefaultToolkit().getScreenSize();
    setLocation(d.width/2 - getWidth()/2, d.height/2 - getHeight()/2);
    setVisible(true);
}

/**
 * Create the main frame's menu bar.
 */
private void makeMenuBar()
{
    final int SHORTCUT_MASK =
        Toolkit.getDefaultToolkit().getMenuShortcutKeyMask();

    JMenuBar menubar = new JMenuBar();
    setJMenuBar(menubar);

    JMenu menu;
    JMenuItem item;

    // create the File menu
    menu = new JMenu("File");
    menubar.add(menu);

    item = new JMenuItem("Quit");
        item.setAccelerator(KeyStroke.getKeyStroke(KeyEvent.VK_Q, SHORTCUT_MASK));
        item.addActionListener(new ActionListener() {
               public void actionPerformed(ActionEvent e) { 
                   quit(); 
               }
           });
    menu.add(item);

}

}

}

1 个解决方案

#1

You set the chosenSeat field immediately after creating the formatList combo box. At that moment, the user has not even had a chance to pick a seat and seat A1 is selected by default. If you set chosenSeat in the play method, it should reflect the seat picked by your user.

在创建formatList组合框后立即设置selectedSeat字段。此时，用户甚至没有机会选择座位，默认情况下选择座位A1。如果您在播放方法中设置selectedSeat，它应该反映您的用户选择的座位。

I think the new JFrame in the play method - as already mentioned by mKorbel - is not needed, since you can use the application frame (this) as the parent component for the call to the JOptionPane.showMessageDialog method:

我认为不需要play方法中的新JFrame - 正如mKorbel已经提到的那样 - 因为你可以使用应用程序框架（this）作为调用JOptionPane.showMessageDialog方法的父组件：

private void play() {
    // todo: frames is not needed.
    //JFrame frames = new JFrame("Sample frame");
    //frames.setSize(400, 400);
    //frames.setVisible(false);
    //frames.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

    chosenSeat = formatList.getSelectedItem().toString();

    // todo: use the application frame as the parent.
    //JOptionPane.showMessageDialog(frames, "You have chosen the seat " + chosenSeat);
    JOptionPane.showMessageDialog(this, "You have chosen the seat " + chosenSeat);
}