Java Swing组件下拉菜单控件JComboBox用法示例

package awtDemo;import java.awt.BorderLayout;import java.awt.Font;import java.awt.event.ActionEvent;import java.awt.event.ActionListener;import java.awt.event.ItemEvent;import java.awt.event.ItemListener;import javax.swing.JComboBox;import javax.swing.JFrame;import javax.swing.JLabel;import javax.swing.event.PopupMenuEvent;import javax.swing.event.PopupMenuListener;public class JComboBoxBasicUseDemo extends JFrame{  private static final long serialVersionUID = -8161981948004677531L;  int DEFAULT_WIDTH = 600;  int DEFAULT_HEIGHT = 400;  private JLabel label;  private JComboBox<String> faceCombo;  private static final int FONTSIZE = 12;    @SuppressWarnings("unused")    public JComboBoxBasicUseDemo(){    setTitle("JComboBoxDemo - www.jb51.net");    setSize(DEFAULT_WIDTH, DEFAULT_HEIGHT);    //添加label    label = new JLabel("欢迎来到编程网 www.jb51.net");    label.setFont(new Font("Serif",Font.PLAIN, FONTSIZE));    add(label, BorderLayout.CENTER);    //actionListener    ActionListener actionListener = new ActionListener(){      public void actionPerformed(ActionEvent e) {        if(e.getSource() instanceof JComboBox){          @SuppressWarnings({ "unchecked", "rawtypes" })          JComboBox<String> comboBox = (JComboBox)e.getSource();          String fontName = comboBox.getSelectedItem().toString();          label.setFont(new Font(fontName, Font.PLAIN, FONTSIZE));          System.out.printf("%s%n", "actionPerformed called");        }      }    };    //popupMenuListener    PopupMenuListener popupMenuListener = new PopupMenuListener() {      @Override      public void popupMenuCanceled(PopupMenuEvent e) {        System.out.println("下拉菜单取消");      }      @SuppressWarnings("unchecked")            @Override      public void popupMenuWillBecomeInvisible(PopupMenuEvent e) {        System.out.println("下拉菜单合上");        JComboBox<String> source = (JComboBox<String>)e.getSource();      }      @Override      public void popupMenuWillBecomeVisible(PopupMenuEvent e) {        System.out.println("下拉菜单弹出");      }    };    //itemListener    ItemListener itemListener = new ItemListener() {      @Override      public void itemStateChanged(ItemEvent arg0) {        // TODO Auto-generated method stub        if(ItemEvent.SELECTED == arg0.getStateChange()){          String selectedItem = arg0.getItem().toString();          label.setFont(new Font(selectedItem, Font.PLAIN, FONTSIZE));          System.out.printf("new selected item : %s%n",selectedItem);        }        if(ItemEvent.DESELECTED == arg0.getStateChange()){          String selectedItem = arg0.getItem().toString();          System.out.printf("deselected item : %s%n",selectedItem);        }      }      };    //添加一个JComboBox    faceCombo = new JComboBox<String>();    faceCombo.setEditable(true);    //faceCombo.addActionListener(actionListener);    //faceCombo.addPopupMenuListener(popupMenuListener);    faceCombo.addItemListener(itemListener);    faceCombo.setEnabled(true);    faceCombo.addItem("Serif");    faceCombo.addItem("SansSerif");    faceCombo.addItem("Monospaced");    faceCombo.addItem("Dialog");    faceCombo.addItem("DialogInput");    add(faceCombo, BorderLayout.SOUTH);  }  public static void main(String[] args) {    // TODO Auto-generated method stub    //创建窗体并指定标题    JComboBoxBasicUseDemo frame = new JComboBoxBasicUseDemo();    //关闭窗体后退出程序    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);    //自动适配所有控件大小    //frame.pack();    //设置窗体位置在屏幕中央    frame.setLocationRelativeTo(null);    //显示窗体    frame.setVisible(true);  }}