帮我看看怎么了?解决就给分~~~~~GUI的问题

Question

你的 display 变量没有定义

Answer 1

你需要将 JLabel display=new JLabel("DEMO1"); 这句话
放到 Demo1 类成员定义部分

Answer 2

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;public class Demo1 extends JPanel
{   JLable display;
String teacherSting="老师";
String studentSting="学生";
String manageSting="管理员";
public Demo1()
{   //创建单选按钮的对象

JRadioButton teacherButton=new JRadioButton("老师");
teacherButton.setMnemonic(KeyEvent.VK_T);
teacherButton.setActionCommand(teacherSting);

JRadioButton studentButton=new JRadioButton("学生");
studentButton.setMnemonic(KeyEvent.VK_S);
studentButton.setActionCommand(studentSting);

JRadioButton manageButton=new JRadioButton("管理员");
manageButton.setMnemonic(KeyEvent.VK_M);
manageButton.setActionCommand(manageSting);

//将单选按钮组成一组,建立单选关系
ButtonGroup group=new ButtonGroup();
group.add(teacherButton);
group.add(studentButton);
group.add(manageButton);

//为按钮添加事件监听器
RadioListener myListener=new RadioListener();
teacherButton.addActionListener(myListener);
studentButton.addActionListener(myListener);
manageButton.addActionListener(myListener);
//建立标签对象
JLabel display=new JLabel("DEMO1");
display.setPreferredSize(new Dimension(180,60));

JPanel radioPanel=new JPanel();
radioPanel.setLayout(new GridLayout(0,1));
    radioPanel.add(teacherButton);
    radioPanel.add(studentButton);
    radioPanel.add(manageButton);
    
setLayout(new BorderLayout());
add(radioPanel,BorderLayout.WEST);
add(display,BorderLayout.CENTER);
setBorder(BorderFactory.createEmptyBorder(20,20,20,0));
}
class RadioListener implements ActionListener
{
public void actionPerformed(ActionEvent e)
{
             display.setText("你选中了"+e.getActionCommand()+".");
}
}

public static void main(String args[])
{
JFrame frame=new JFrame("DEMO1");
frame.addWindowListener(new WindowAdapter()
{
public void windowClosing(WindowEvent e)
{
System.exit(0);
}
});
frame.getContentPane().add(new Demo1(),BorderLayout.CENTER);
frame.pack();
frame.setVisible(true);
}
}
--------------------------------------------------D:\chengji>javac Demo1.java
Demo1.java:6: cannot resolve symbol
symbol  : class JLable
location: class Demo1
{   JLable display;
    ^
1 error
这样的错误
还有你的第三句话我们明白
不好意思
楼上~~~~~~~~~~~~~~~~

Answer 3

是 JLabel 不是 JLable
在函数内定义的变量,当函数返后便作废
所以 GUI 组件应该定义为类成员

Answer 4

谢谢啊
不过解释之后
当我选一个时
dos里出现很多异常
我复制不了啊
急啊~~~

Answer 5

将你的组件全部定义为类成员, 然后用构造函数进行初试化
例如
public class Demo1 extends JPanel {
    private JLabel display;
    ... ...
    public Demo1() {
        ... ...
        display = new JLabel("DEMO1");
        ... ...
    }
    ... ...
}

Answer 6

再帮你一把import java.awt.*;
import java.awt.event.*;
import javax.swing.*;public class Demo1 extends JPanel
{   JLabel display;
String teacherSting="老师";
String studentSting="学生";
String manageSting="管理员";
public Demo1()
{   //创建单选按钮的对象

JRadioButton teacherButton=new JRadioButton("老师");
teacherButton.setMnemonic(KeyEvent.VK_T);
teacherButton.setActionCommand(teacherSting);

JRadioButton studentButton=new JRadioButton("学生");
studentButton.setMnemonic(KeyEvent.VK_S);
studentButton.setActionCommand(studentSting);

JRadioButton manageButton=new JRadioButton("管理员");
manageButton.setMnemonic(KeyEvent.VK_M);
manageButton.setActionCommand(manageSting);

//将单选按钮组成一组,建立单选关系
ButtonGroup group=new ButtonGroup();
group.add(teacherButton);
group.add(studentButton);
group.add(manageButton);

//为按钮添加事件监听器
RadioListener myListener=new RadioListener();
teacherButton.addActionListener(myListener);
studentButton.addActionListener(myListener);
manageButton.addActionListener(myListener);
//建立标签对象
display=new JLabel("DEMO1");
display.setPreferredSize(new Dimension(180,60));

JPanel radioPanel=new JPanel();
radioPanel.setLayout(new GridLayout(0,1));
    radioPanel.add(teacherButton);
    radioPanel.add(studentButton);
    radioPanel.add(manageButton);
    
setLayout(new BorderLayout());
add(radioPanel,BorderLayout.WEST);
add(display,BorderLayout.CENTER);
setBorder(BorderFactory.createEmptyBorder(20,20,20,0));
}
class RadioListener implements ActionListener
{
public void actionPerformed(ActionEvent e)
{
             display.setText("你选中了"+e.getActionCommand()+".");
             
}
}

public static void main(String args[])
{
JFrame frame=new JFrame("DEMO1");
frame.addWindowListener(new WindowAdapter()
{
public void windowClosing(WindowEvent e)
{
System.exit(0);
}
});
frame.getContentPane().add(new Demo1(),BorderLayout.CENTER);
frame.pack();
frame.setVisible(true);
}
}

Answer 7

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;public class Demo1 extends JPanel
{
String teacherSting="老师";
String studentSting="学生";
String manageSting="管理员";

JLabel display=new JLabel("DEMO1");
public Demo1()
{   //创建单选按钮的对象

JRadioButton teacherButton=new JRadioButton("老师");
teacherButton.setMnemonic(KeyEvent.VK_T);
teacherButton.setActionCommand(teacherSting);

JRadioButton studentButton=new JRadioButton("学生");
studentButton.setMnemonic(KeyEvent.VK_S);
studentButton.setActionCommand(studentSting);

JRadioButton manageButton=new JRadioButton("管理员");
manageButton.setMnemonic(KeyEvent.VK_M);
manageButton.setActionCommand(manageSting);

//将单选按钮组成一组,建立单选关系
ButtonGroup group=new ButtonGroup();
group.add(teacherButton);
group.add(studentButton);
group.add(manageButton);

//为按钮添加事件监听器
RadioListener myListener=new RadioListener();
teacherButton.addActionListener(myListener);
studentButton.addActionListener(myListener);
manageButton.addActionListener(myListener);
//建立标签对象

display.setPreferredSize(new Dimension(180,60));

JPanel radioPanel=new JPanel();
radioPanel.setLayout(new GridLayout(0,1));
         radioPanel.add(teacherButton);
         radioPanel.add(studentButton);
         radioPanel.add(manageButton);
    
setLayout(new BorderLayout());
add(radioPanel,BorderLayout.WEST);
add(display,BorderLayout.CENTER);
setBorder(BorderFactory.createEmptyBorder(20,20,20,0));
}
class RadioListener implements ActionListener
{
public void actionPerformed(ActionEvent e)
{
             display.setText("你选中了"+e.getActionCommand()+".");
}
}

public static void main(String args[])
{
JFrame frame=new JFrame("DEMO1");
frame.addWindowListener(new WindowAdapter()
{
public void windowClosing(WindowEvent e)
{
System.exit(0);
}
});
frame.getContentPane().add(new Demo1(),BorderLayout.CENTER);
frame.pack();
frame.setVisible(true);
}
}这个我编译过，绝对没问题