Java键盘事件监听(2)修改：使用监听键盘事件，而不是改写JTextField

package com.han;import java.awt.Container;import java.awt.FlowLayout;import java.awt.event.KeyAdapter;import java.awt.event.KeyEvent;import javax.swing.JFrame;import javax.swing.JLabel;import javax.swing.JOptionPane;import javax.swing.JTextField;/** * 键盘事件监听(2)修改：使用监听键盘事件，而不是改写JTextField * @author HAN * */public class KeyEvent_2_Modified extends JFrame {/** *  */private static final long serialVersionUID = -3184139070064852786L;public KeyEvent_2_Modified() {// TODO Auto-generated constructor stubfinal Container container = getContentPane();container.setLayout(new FlowLayout());JLabel label = new JLabel("实现只允许输入数字的文本框：");final JTextField textField = new JTextField(10);container.add(label);container.add(textField);textField.addKeyListener(new KeyAdapter() {@Overridepublic void keyPressed(KeyEvent e) { // keyPressed 与 keyReleased是有时间差的！！// TODO Auto-generated method stubif (e.getKeyCode() == KeyEvent.VK_ENTER) {char[] text = textField.getText().toCharArray();for (char ch : text) {if (!Character.isDigit(ch)) {//textField.removeKeyListener(this);JOptionPane.showMessageDialog(container, "Your input contains non-digit characters !", "Warning", JOptionPane.WARNING_MESSAGE);textField.setText("");//textField.addKeyListener(this);return;}}}}});}/** * @param args */public static void main(String[] args) {// TODO Auto-generated method stubKeyEvent_2_Modified frame = new KeyEvent_2_Modified();frame.setTitle("实现只允许输入数字的文本框(2)");frame.pack();frame.setVisible(true);frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);}}