Swing KeyListener介面

類處理該KeyEvent類的物件應該實現這個介面。一個元件必須註冊。使用addKeyListener()方法，該物件可以被註冊。

介面宣告

以下是宣告 java.awt.event.KeyListener介面：

public interface KeyListener
   extends EventListener

介面方法

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.

方法繼承

這個介面從以下介面繼承的方法：

• java.awt.EventListener

KeyListener 例子

選擇使用任何編輯器建立以下java程式在 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) {
      }   
   }
}

編譯程式，使用命令提示字元。到 D:/ > SWING 然後輸出以下命令。

D:SWING>javac comyiibaiguiSwingListenerDemo.java

如果沒有錯誤出現，這意味著編譯成功。使用下面的命令來執行程式。

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

驗證下面的輸出