java ButtonGroup及JRadioButton用法

package com.xinhua.testswing;

import java.awt.event.ActionEvent;

import java.awt.event.ActionListener;

import java.awt.event.ItemEvent;

import java.awt.event.ItemListener;

import javax.swing.ButtonGroup;

import javax.swing.JFrame;

import javax.swing.JPanel;

import javax.swing.JRadioButton;

public class TestJRadioButton extends JFrame {

JRadioButton jrb1;

JRadioButton jrb2;

JRadioButton jrb3;

JRadioButton jrb4;

public TestJRadioButton() {

jrb1 = new JRadioButton("china");

jrb2 = new JRadioButton("usa");

jrb3 = new JRadioButton("Egl");

jrb4 = new JRadioButton("fra");

ButtonGroup bg = new ButtonGroup();

bg.add(jrb1);

bg.add(jrb2);

bg.add(jrb3);

bg.add(jrb4);

// jp.add(bg);

JPanel jp = new JPanel();

jp.add(jrb1);

jp.add(jrb2);

jp.add(jrb3);

jp.add(jrb4);

//注意jrb1,jrb2,jrb3,jrb4被添加两次，一次是加入到ButtonGroup中，一次是JPanel中，但ButtonGroup不需要被添加

getContentPane().add(jp);

jrb1.addItemListener(new ItemListener() {

@Override

public void itemStateChanged(ItemEvent e) {

if (jrb1.isSelected()) {

System.out.println(jrb1.getText());

}

}

});

jrb2.addItemListener(new ItemListener() {

@Override

public void itemStateChanged(ItemEvent e) {

if (jrb2.isSelected()) {

System.out.println(jrb2.getText());

}

}

});

jrb3.addItemListener(new ItemListener() {

@Override

public void itemStateChanged(ItemEvent e) {

if (jrb3.isSelected()) {

System.out.println(jrb3.getText());

}

}

});

jrb4.addItemListener(new ItemListener() {

@Override

public void itemStateChanged(ItemEvent e) {

if (jrb4.isSelected()) {

System.out.println(jrb4.getText());

}

}

});

setSize(300, 200);

setVisible(true);

}

public static void main(String[] args) {

new TestJRadioButton();

}

}