一个java的小程序中的问题 关于单选按钮的

来源：百度知道 编辑：UC知道 时间：2024/06/07 09:53:48
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;

public class CheckBoxDemo1 extends JFrame implements ItemListener
{
private JTextArea jta;
public CheckBoxDemo1()
{
setTitle("Check Box Demo");
setLocation(150,150);

jta=new JTextArea("Welcome to Java!",5,20);
jta.setFont(new Font("Serif",Font.PLAIN,20));
jta.setBackground(Color.pink);

JPanel p=new JPanel();
p.setLayout(new FlowLayout());

ButtonGroup bgroup=new ButtonGroup();
JRadioButton button20=new JRadioButton("20",true);
bgroup.add(button20);
p.add(button20);
JRadioButton button30=new JRadioButton("30",false);
bgroup.add(button30);
p.add(button30);
JRadioButton button60=new JRadioButton("60",false);
bgroup.add(button60);
p.add(button60);

getContentPane().setLayout(ne

button20, button30, button60 定义在里面了，另外那个方法看不到他们。

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;

public class CheckBoxDemo1 extends JFrame implements ItemListener {
private JTextArea jta;
JRadioButton button20, button30, button60;
public CheckBoxDemo1() {
setTitle("Check Box Demo");
setLocation(150, 150);

jta = new JTextArea("Welcome to Java!", 5, 20);
jta.setFont(new Font("Serif", Font.PLAIN, 20));
jta.setBackground(Color.pink);

JPanel p = new JPanel();
p.setLayout(new FlowLayout());

ButtonGroup bgroup = new ButtonGroup();
button20 = new JRadioButton("20", true);
bgroup.add(button20);
p.add(button20);
button30 = new JRadioButton("30", false);
bgroup.add(button30);
p.add(button30);
button60 = new JRadioButton("60", false);
bgroup