menuItems单击时未打开Java内部面板
menuItems单击时未打开Java内部面板
提问于 2014-03-26 19:35:00
我试图建立一个小程序，其中有3个菜单项，学生，大学，和出口。我已经差不多完成了，它编译，但学生和大学的菜单项未能打开内部java面板。
这是我的Java 2评论(我真的需要分数)的额外学分问题，作业问题如下：
编写一个程序，用菜单构建桌面应用程序，菜单上有大学面板和学生面板。大学小组有名称和州代码。“学生”面板有名称和id。用户可以分别键入大学或学生的名称和代码或id。每个面板都有一个接受数据、清除字段和重置焦点的提交按钮。每个面板都有一个检查输入方法。Id是一个整数。大学或学生的数据被放置在各自的数组中。
我有一个工作上的例子，我不知道我做错了什么。当单击“学生和大学”时，面板将不会打开。
import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
import java.util.*;
import java.io.*;
public class Question4 extends JFrame
{
private JDesktopPane theDesktop;
ArrayList<Student> studentList = new ArrayList<Student>();
ArrayList<University> universityList = new ArrayList<University>();
public static void main(String args[])
{
Question4 q4 = new Question4();
q4.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
q4.setSize(400,400);
q4.setLocationRelativeTo(null);
q4.setVisible(true);
}
public Question4()
{
super("Question 4");
theDesktop = new JDesktopPane();
JMenuBar bar = new JMenuBar();
JMenu menu = new JMenu("Menu");
JMenuItem studentItem = new JMenuItem("Student");
JMenuItem universityItem = new JMenuItem("University");
JMenuItem exitItem = new JMenuItem("Exit");
exitItem.addActionListener(new ActionListener()
{
public void actionPerformed(ActionEvent ae)
{
System.exit(0);
}
});
studentItem.addActionListener(new ActionListener()
{
public void actionPerformed(ActionEvent ae)
{
JInternalFrame sFrame = new JInternalFrame("Student",true,true,true);
AddStudentPanel sPanel = new AddStudentPanel();
sFrame.add(sPanel);
sFrame.pack();
theDesktop.add(sFrame);
sFrame.setVisible(true);
}
});
universityItem.addActionListener(new ActionListener()
{
public void actionPerformed(ActionEvent ae)
{
JInternalFrame uFrame = new JInternalFrame("University",true,true,true);
AddUniversityPanel uPanel = new AddUniversityPanel();
uFrame.add(uPanel);
uFrame.pack();
theDesktop.add(uFrame);
uFrame.setVisible(true);
}
});
menu.add(studentItem);
menu.add(universityItem);
menu.add(exitItem);
bar.add(menu);
setJMenuBar(bar);
add(theDesktop);
}
private class AddStudentPanel extends JPanel
{
private JLabel nameLabel;
private JLabel idLabel;
private JLabel submitLabel;
private JTextField nameField;
private JTextField idField;
private JButton submitButton;
public AddStudentPanel()
{
setLayout(new GridLayout (3,2));
nameLabel = new JLabel("Enter Name");
idLabel = new JLabel("Enter ID");
submitLabel = new JLabel("Submit");
nameField = new JTextField(15);
idField = new JTextField(15);
StudentHandler sHandler = new StudentHandler();
submitButton.addActionListener(sHandler);
add(nameLabel);
add(nameField);
add(idLabel);
add(idField);
add(submitLabel);
add(submitButton);
}
class StudentHandler implements ActionListener
{
public void actionPerformed(ActionEvent ae)
{
if(ae.getSource() == submitButton)
{
if(checkStudentInput())
{
studentList.add(new Student(nameField.getText(),Integer.parseInt(idField.getText())));
nameField.setText("");
idField.setText("");
nameField.requestFocus();
}
}
}
public boolean checkStudentInput()
{
boolean input = true;
if(nameField.getText().isEmpty())
{
JOptionPane.showMessageDialog(null,"Please enter a name");
nameField.requestFocus();
input = false;
}
else if(idField.getText().isEmpty())
{
JOptionPane.showMessageDialog(null,"Please enter an id");
idField.requestFocus();
input = false;
}
else
{
try
{
Integer.parseInt(idField.getText());
}catch(NumberFormatException nfe)
{
JOptionPane.showMessageDialog(null,"Please enter an integer for id");
idField.setText("");
idField.requestFocus();
input = false;
}
}
return input;
}
}
}
private class AddUniversityPanel extends JPanel
{
private JLabel nameLabel;
private JLabel codeLabel;
private JLabel submitLabel;
private JTextField nameField;
private JTextField codeField;
private JButton submitButton;
public AddUniversityPanel()
{
setLayout(new GridLayout (3,2));
nameLabel = new JLabel("Enter Name");
codeLabel = new JLabel("Enter State Code");
submitLabel = new JLabel("Submit");
nameField = new JTextField(15);
codeField = new JTextField(15);
UniversityHandler uHandler = new UniversityHandler();
submitButton.addActionListener(uHandler);
add(nameLabel);
add(nameField);
add(codeLabel);
add(codeField);
add(submitLabel);
add(submitButton);
}
class UniversityHandler implements ActionListener
{
public void actionPerformed(ActionEvent ae)
{
if(ae.getSource() == submitButton)
{
if(checkUniversityInput())
{
universityList.add(new University(nameField.getText(),Integer.parseInt(codeField.getText())));
nameField.setText("");
codeField.setText("");
nameField.requestFocus();
}
}
}
public boolean checkUniversityInput()
{
boolean input = true;
if(nameField.getText().isEmpty())
{
JOptionPane.showMessageDialog(null,"Please enter a name");
nameField.requestFocus();
input = false;
}
else if(codeField.getText().isEmpty())
{
JOptionPane.showMessageDialog(null,"Please enter an State Code");
codeField.requestFocus();
input = false;
}
else
{
try
{
Integer.parseInt(codeField.getText());
}catch(NumberFormatException nfe)
{
JOptionPane.showMessageDialog(null,"Please enter an integer for State Code");
codeField.setText("");
codeField.requestFocus();
input = false;
}
}
return input;
}
}
}
}回答 1
Stack Overflow用户
回答已采纳
发布于 2014-03-26 19:56:48
换行
add(theDesktop);至
setContentPane(theDesktop);你应该可以继续。
您还需要在submitButton和AddStudentPanel中初始化NullPointerException以避免NullPointerException。
submitButton = new JButton()希望这能帮助你完成你的任务。
页面原文内容由Stack Overflow提供。腾讯云小微IT领域专用引擎提供翻译支持
原文链接：
https://stackoverflow.com/questions/22671319
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