回复 9楼 诸葛修勤
但我试了，没用。。其他的代码是对的。。。我才在menu那出错了。。
程序代码：import java.awt.Button;
import java.awt.CardLayout;
import java.awt.Container;
import java.awt.Frame;
import java.awt.Label;
import java.awt.Menu;
import java.awt.MenuBar;
import java.awt.MenuItem;
import java.awt.Panel;
import java.awt.TextArea;
import java.awt.TextField;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.WindowAdapter;
import java.awt.event.WindowEvent;
import java.util.Iterator;
import java.util.LinkedList;
import javax.swing.Box;
public class main {
public static void main(String args[])
{
new yxf();
}
}
class student
{
student(String id, String name, double mark)
{
m_id = new String(id);
m_name = new String(name);
m_mark = mark;
}
String show_id (){ return m_id;}
String show_name() {return m_name;}
double show_mark() { return m_mark;}
private String m_id = null;//学生的学号
private String m_name = null;//学生的姓名
private double m_mark = 0;//学生的成绩
}
class yxf extends Frame implements ActionListener
{
LinkedList<student> list = null;//定义一个链表
Panel panel_add = null;
Panel panel_show = null;
MenuBar menubar = null;
Menu menu = null;
MenuItem menu_add = null;
MenuItem menu_show = null;
CardLayout card = null;
yxf()
{
super("学生管理系统");
card = new CardLayout();
setLayout(card);
panel_add = new add(this, list);
add("添加",panel_add);
panel_show = new show(this, list);
add("显示", panel_show);
menu = new Menu("功能");
menu_add = new MenuItem("添加");
menu_add.addActionListener(this);
menu_show = new MenuItem("显示");
menu_show.addActionListener(this);
menu.add(menu_add);
menu.add(menu_show);
menubar = new MenuBar();
menubar.add(menu);
setMenuBar(menubar);
addWindowListener(new WindowAdapter()
{
public void windowClosing(WindowEvent e)
{
System.exit(0);
}
});
setBounds(100, 100, 280, 200);
setVisible(true);
validate();
}
@Override
public void actionPerformed(ActionEvent e) {
// TODO Auto-generated method stub
if (e.getSource() == menu_add)
{
card.show(this, "添加");
System.out.println(1);
setSize(280, 200);
}
else if (e.getSource() == menu_show)
{
card.show(this, "显示");
System.out.println(2);
setSize(280, 300);
}
}
}
//定义添加信息的类
class add extends Panel implements ActionListener
{
LinkedList<student> list = null;
Button ack = null;//确认按钮
Button cancel = null;//取消按钮
TextField tf_id;
TextField tf_name;
TextField tf_mark;
add(Container con, LinkedList<student> list)
{
this.list = list;
Box box1 = Box.createVerticalBox();
Box box2 = Box.createVerticalBox();
box1.add(new Label("学号："));
box1.add(Box.createVerticalStrut(4));
box1.add(new Label("姓名："));
box1.add(Box.createVerticalStrut(4));
box1.add(new Label("成绩："));
box1.add(Box.createVerticalStrut(4));
cancel = new Button("重置");
cancel.addActionListener(this);
box1.add(cancel);
tf_id = new TextField(10);
tf_name = new TextField(10);
tf_mark = new TextField(10);
box2.add(tf_id);
box2.add(Box.createVerticalStrut(4));
box2.add(tf_name);
box2.add(Box.createVerticalStrut(4));
box2.add(tf_mark);
box2.add(Box.createVerticalStrut(4));
ack = new Button("确定");
ack.addActionListener(this);
box2.add(ack);
add(box1);
add(box2);
}
@Override
public void actionPerformed(ActionEvent e) {
// TODO Auto-generated method stub
if (e.getSource() == cancel)
{
tf_id.setText(null);
tf_name.setText(null);
tf_mark.setText(null);
}
else if (e.getSource() == ack)
{
if (null == list)
{
list = new LinkedList<student>();
}
list_add();
}
}
//向链表中添加数据
void list_add()
{
String str_id = new String(tf_id.getText());
String str_name = new String(tf_name.getText());
double dou = 0;
try
{
dou = Double.parseDouble(tf_mark.getText());
list.add(new student(str_id, str_name, dou));
}
catch (NumberFormatException e)
{
System.out.println("错误:"+e.getMessage());
}
}
}
//定义显示信息的类
class show extends Panel
{
LinkedList<student> list = null;
TextArea ta_show = null;
show(Container con, LinkedList<student> list)
{
this.list = list;
ta_show = new TextArea(10, 20);
add(ta_show);
show_list();
setVisible(true);
validate();
}
public void set_list(LinkedList<student> list)
{
this.list = list;
}
public void show_list()
{
if (null == list)
{
ta_show.append("没有数据\n");
return;
}
try
{
Iterator<student> iter = list.iterator();
ta_show.setText(null);
while (iter.hasNext())
{
student temp = (student)iter.next();
ta_show.append("学号："+temp.show_id()+" 姓名："+temp.show_name()+" 成绩："+temp.show_mark()+"\n");
}
}
catch (NullPointerException e)
{
System.out.println("Iterator " +e.getMessage());
}
}
}
