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 stub
    final 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() {

      @Override
      public void keyPressed(KeyEvent e) { // keyPressed 与 keyReleased是有时间差的！！
        // TODO Auto-generated method stub
        if (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 stub
    KeyEvent_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);
  }

}