我希望在第一个comboBox中选择的城市不出现在第二个comboBox中 [英] I want the city selected in the first comboBox not to appear in the second comboBox

问题描述

在此处截屏如果我选择的城市来自:comboBox，则不应出现在TO:comboBox中.如何为该actionListener的actionListener编写代码?

Screenshot hereIf I choose a city FROM: comboBox then it shouldn't appear in TO: comboBox. How can I code the actionListener of this actionListener?

我的代码在这里:

公共类CityFromTo {

public class CityFromTo {

public static void main(String[] args) {
    
    String[] cFrom = {"Choose", "Istanbul", "New York", "London", "Milano", "Tokyo", "Paris", "Moscow", "Elâzığ"};
    String[] cTo = {"Choose", "Istanbul", "New York", "London", "Milano", "Tokyo", "Paris", "Moscow", "Elâzığ"};
    
    JLabel from = new JLabel("FROM : ");
    JLabel to = new JLabel("   TO : ");
    
    
    JComboBox comboFrom = new JComboBox(cFrom);
    JComboBox comboTo = new JComboBox(cTo);
    
    JFrame frame = new JFrame();
    frame.setLayout(new FlowLayout());
    
    
    frame.add(from);
    frame.add(comboFrom);
    frame.add(to);
    frame.add(comboTo);
    
    frame.setSize(400, 350);
    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    frame.setLocationRelativeTo(null);
    frame.setVisible(true);
    
    

}

}

推荐答案

我对您的代码进行了重新设计，以使其脱离静态.您只需要一个城市列表即可到达 JComboBoxes .

I reworked your code to get away from static. You only need one list of cities for your from and to JComboBoxes.

您使用 ActionListener 侦听 JComboBox 中的更改，并将城市从 JComboBox 中删除.我们通过删除所有城市并将其一次又一次添加回去来删除该城市.这使用户可以改变对城市的想法.

You use an ActionListener to listen for changes in the from JComboBox, and remove the city from the to JComboBox. We remove the city by removing all the cities and adding them back, one at a time. This allows the user to change his mind about the from city.

这是完整的可运行代码.

Here's the complete runnable code.

import java.awt.BorderLayout;
import java.awt.Dimension;
import java.awt.FlowLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;

import javax.swing.BorderFactory;
import javax.swing.JComboBox;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.SwingUtilities;

public class CityFromTo implements Runnable {
    
    public static void main(String[] args) {
       SwingUtilities.invokeLater(new CityFromTo());
    }
    
    private JComboBox<String> comboFrom;
    private JComboBox<String> comboTo;
    
    private String[] cities = {"Choose", "Istanbul", "New York", "London", 
            "Milano", "Tokyo", "Paris", "Moscow", "Elâzığ"};

    @Override
    public void run() {
        JFrame frame = new JFrame();
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        
        frame.add(createMainPanel(), BorderLayout.CENTER);
        
        frame.pack();
        frame.setLocationRelativeTo(null);
        frame.setVisible(true);
    }
    
    private JPanel createMainPanel() {
        JPanel panel = new JPanel(new FlowLayout());
        panel.setBorder(BorderFactory.createEmptyBorder(5, 5, 5, 5));
        panel.setPreferredSize(new Dimension(400, 350));
        
        JLabel from = new JLabel("FROM : ");
        panel.add(from);
        
        comboFrom = new JComboBox<>(cities);
        comboFrom.addActionListener(new FromListener());
        panel.add(comboFrom);
        
        JLabel to = new JLabel("   TO : ");
        panel.add(to);
        
        comboTo = new JComboBox<>(cities);
        panel.add(comboTo);
        
        return panel;
    }
    
    public class FromListener implements ActionListener {

        @Override
        public void actionPerformed(ActionEvent event) {
            String city = (String) comboFrom.getSelectedItem();
            comboTo.removeAllItems();
            for (String s : cities) {
                if (!s.equals(city)) {
                    comboTo.addItem(s);
                }
            }
        }
        
    }

}

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