Swing如何使用下拉式方塊？

下面的範例展示了如何在Java Swing應用程式中使用標準下拉式方塊。

使用以下API -

• JComboBox - 建立標準下拉式方塊。
• JCheckBox.setSelectedIndex(index); - 選擇專案。
• JCheckBox.getSelectedItem(); - 獲取所選專案。

範例

package com.yiibai.swingdemo;

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

import javax.swing.JComboBox;
import javax.swing.JFrame;
import javax.swing.JOptionPane;
import javax.swing.JPanel;

public class SwingTester {
   public static void main(String[] args) {
      createWindow();
   }

   private static void createWindow() {    
      JFrame frame = new JFrame("Swing使用下拉式方塊(tw511.com)");
      frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
      createUI(frame);
      frame.setSize(560, 200);      
      frame.setLocationRelativeTo(null);  
      frame.setVisible(true);
   }

   private static void createUI(final JFrame frame){  
      JPanel panel = new JPanel();
      LayoutManager layout = new FlowLayout();  
      panel.setLayout(layout);       

      String[] sites = {"Tw511.com", "kaops.com", "Viibm.com", "google.com", "Baidu.com"};
      JComboBox<String> comboBox = new JComboBox<>(sites);
      comboBox.setSelectedIndex(3);
      comboBox.addActionListener(new ActionListener() {
         public void actionPerformed(ActionEvent e) {
            JComboBox combo = (JComboBox)e.getSource();
            JOptionPane.showMessageDialog(frame,combo.getSelectedItem());

         }
      });
      panel.add(comboBox);   
      frame.getContentPane().add(panel, BorderLayout.CENTER);    
   }
}

執行上面範例程式碼，得到以下結果：