JavaSE series code 58: Menu bar design and corresponding event handling

Java 1.2 introduces a new GUI component library called swing. § swing includes javax.swing package and its subpackages. § swing has a platform independent implementation and an attribute set of artistic state. § although swing is independent of AWT, it is implemented according to the basic AWT class.

import java.awt.*;
import java.awt.event.*;
public class Javase_58 extends Frame implements ActionListener,ItemListener
{
  static Javase_58 frm=new Javase_58 ();
  static MenuBar mb=new MenuBar();      //创建MenuBar对象mb
  static Menu m1=new Menu("颜色");      //创建Menu对象m1
  static Menu m2=new Menu("窗口");      //创建Menu对象m2
  static MenuItem mi1=new MenuItem("红色");  //创建MenuItem对象mi1
  static MenuItem mi2=new MenuItem("绿色");
  static MenuItem mi3=new MenuItem("蓝色");
  static MenuItem mi4=new MenuItem("关闭");
  static CheckboxMenuItem cbmi=new CheckboxMenuItem("斜体"); //复选框菜单项
  static PopupMenu pm=new PopupMenu("弹出式菜单");   //创建弹出式菜单
  static MenuItem Pop_m1,Pop_m2,Pop_m3;        //弹出菜单项
  static TextArea ta=new TextArea ("菜单程序设计",10,30);
  public static void main(String[] args)
  {
    frm.setLayout(null);    //取消页面设置
    frm.setLocation(100,80);
    frm.setSize(260,170);
    frm.add(ta);
    ta.setBounds(40,65,180,80); 
    mb.add(m1);        //将m1加入到mb中
    mb.add(m2);
    m1.add(mi1);        //将mi1加入到m1中
    m1.add(mi2);
    m1.add(mi3);
    m1.addSeparator();    //加一分隔线
    m1.add(cbmi);       //添加带复选框的菜单项
    m2.add(mi4);        //将mi4加入到m2中
    frm.setMenuBar(mb);            //设置frm的菜单栏为mb
    Pop_m1= new MenuItem("红色");
    Pop_m2= new MenuItem("绿色");
    Pop_m3= new MenuItem("蓝色");
    pm.add(Pop_m1);     //向弹出式菜单中添加菜单项
    pm.add(Pop_m2);
    pm.add(Pop_m3);
    Pop_m1.addActionListener(frm);   //设置frm为弹出菜单项的监听者
    Pop_m2.addActionListener(frm);
    Pop_m3.addActionListener(frm);
    frm.add(pm);              //将弹出式菜单附加在frm上
    ta.addMouseListener (new MyMouseList());   //设置内部类为ta的监听者
    mi1.addActionListener(frm);      //设置frm为mi1的事件监听者
    mi2.addActionListener(frm); 
    mi3.addActionListener(frm);
    cbmi.addItemListener(frm);       //设置frm为带复选框菜单项的监听者
    mi4.addActionListener(frm);
    frm.setVisible(true);
  }
  public void actionPerformed(ActionEvent e)  //事件处理的程序代码
  {
    MenuItem mi=(MenuItem)e.getSource();   //取得引发事件的对象
    String miLab=mi.getLabel();             //取得菜单项的文字标题
    if(miLab=="红色")
      ta.setForeground(Color.red);
    else if(miLab=="绿色")
      ta.setForeground (Color.green);
    else if(miLab=="蓝色")
      ta.setForeground (Color.blue);
    else if(mi==mi4)
      frm.dispose();        //关闭窗口，释放资源
    frm.setTitle("设置文字颜色为【"+miLab+"】");
  }
  public void itemStateChanged(ItemEvent ie)  //处理复选框菜单项的方法
  {
    boolean yn= cbmi.getState();
    if (yn) ta.setFont(new Font("楷体_GB2312",Font.ITALIC,15));
    else ta.setFont(new Font("宋体",Font.PLAIN,15));
  }
  static class MyMouseList extends MouseAdapter    //处理鼠标事件的类
  {
    public void mouseReleased(MouseEvent mce)    //释放鼠标时触发的事件
    {
      if (mce.isPopupTrigger())     //判断鼠标事件是否是由弹出菜单引发
        pm.show((Component)mce.getSource(),mce.getX(),mce.getY()); 
    }
  }
}