类处理该KeyEvent类的对象应该实现这个接口。一个组件必须注册。使用addKeyListener()方法，该对象可以被注册。

接口声明

以下是声明 java.awt.event.KeyListener接口：

public interface KeyListener
   extends EventListener

接口方法

S.N.	方法 & 描述
1	void keyPressed(KeyEvent e)  Invoked when a key has been pressed.
2	void keyReleased(KeyEvent e)  Invoked when a key has been released.
3	void keyTyped(KeyEvent e)  Invoked when a key has been typed.

方法继承

这个接口从以下接口继承的方法：

• java.awt.EventListener

KeyListener 例子

选择使用任何编辑器创建以下java程序在 D:/ > SWING > com > yiibai > gui >

SwingListenerDemo.java

package com.yiibai.gui;

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

public class SwingListenerDemo {
   private JFrame mainFrame;
   private JLabel headerLabel;
   private JLabel statusLabel;
   private JPanel controlPanel;

   public SwingListenerDemo(){
      prepareGUI();
   }

   public static void main(String[] args){
      SwingListenerDemo  swingListenerDemo = new SwingListenerDemo();  
      swingListenerDemo.showKeyListenerDemo();
   }

   private void prepareGUI(){
      mainFrame = new JFrame("Java SWING Examples");
      mainFrame.setSize(400,400);
      mainFrame.setLayout(new GridLayout(3, 1));

      headerLabel = new JLabel("",JLabel.CENTER );
      statusLabel = new JLabel("",JLabel.CENTER);        

      statusLabel.setSize(350,100);
      mainFrame.addWindowListener(new WindowAdapter() {
         public void windowClosing(WindowEvent windowEvent){
	        System.exit(0);
         }        
      });    
      controlPanel = new JPanel();
      controlPanel.setLayout(new FlowLayout());

      mainFrame.add(headerLabel);
      mainFrame.add(controlPanel);
      mainFrame.add(statusLabel);
      mainFrame.setVisible(true);  
   }

   private JTextField textField;
   private void showKeyListenerDemo(){
      headerLabel.setText("Listener in action: KeyListener");      
      textField  = new JTextField(10);

      textField.addKeyListener(new CustomKeyListener());
      JButton okButton = new JButton("OK");
      okButton.addActionListener(new ActionListener() {
         public void actionPerformed(ActionEvent e) {
            statusLabel.setText("Entered text: " 
               + textField.getText());                
         }
      });

      controlPanel.add(textField);
      controlPanel.add(okButton);    
      mainFrame.setVisible(true);  
   }

   class CustomKeyListener implements KeyListener{
      public void keyTyped(KeyEvent e) {
      }

      public void keyPressed(KeyEvent e) {
         if(e.getKeyCode() == KeyEvent.VK_ENTER){
            statusLabel.setText("Entered text: " 
               + textField.getText());
         }
      }

      public void keyReleased(KeyEvent e) {
      }   
   }
}

编译程序，使用命令提示符。到 D:/ > SWING 然后输出以下命令。

D:SWING>javac comyiibaiguiSwingListenerDemo.java

如果没有错误出现，这意味着编译成功。使用下面的命令来运行程序。

D:SWING>java com.yiibai.gui.SwingListenerDemo

验证下面的输出