SWING - FocusAdapter 类

简介

FocusAdapter 类是一个用于接收键盘焦点事件的抽象（适配器）类。此类的所有方法均为空。此类是一个便利类，用于创建侦听器对象。

类声明

以下是 java.awt.event.FocusAdapter 类的声明 −

public abstract class FocusAdapter
   extends Object
      implements FocusListener

类构造函数

类方法

继承的方法

此类继承了以下类的这些方法 −

• java.lang.Object

FocusAdapter 实例

使用您选择的任何编辑器，在 D:/ > SWING > com > tutorialspoint > gui > 内创建以下 Java 程序。

SwingAdapterDemo.java

package com.tutorialspoint.gui;

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

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

   public SwingAdapterDemo(){
      prepareGUI();
   }
   public static void main(String[] args){
      SwingAdapterDemo  swingAdapterDemo = new SwingAdapterDemo();        
      swingAdapterDemo.showFocusAdapterDemo();
   }
   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 void showFocusAdapterDemo(){
      headerLabel.setText("Listener in action: FocusAdapter");      
      JButton okButton = new JButton("OK");
      JButton cancelButton = new JButton("Cancel");
      
      okButton.addFocusListener(new FocusAdapter() { 
         public void focusGained(FocusEvent e) {
            statusLabel.setText(statusLabel.getText() 
               + e.getComponent().getClass().getSimpleName() 
               + " gained focus. ");
         }
      });  
      cancelButton.addFocusListener(new FocusAdapter(){
         public void focusLost(FocusEvent e) {
            statusLabel.setText(statusLabel.getText() 
               + e.getComponent().getClass().getSimpleName() 
               + " lost focus. ");
         }
      });  
      controlPanel.add(okButton);
      controlPanel.add(cancelButton);     
      mainFrame.setVisible(true);  
   }
}

使用命令提示符编译程序。转到 D:/ > SWING 并输入以下命令。

D:\SWING>javac com\tutorialspoint\gui\SwingAdapterDemo.java

如果未出现错误，则表示编译成功。使用以下命令运行程序。

D:\SWING>java com.tutorialspoint.gui.SwingAdapterDemo

验证以下输出。