FocusListener

介绍 (Introduction)

FocusListener接口用于接收键盘焦点事件。 处理焦点事件的类需要实现此接口。

Class 声明 (Class Declaration)

以下是java.awt.event.FocusListener接口的声明 -

public interface FocusListener
extends EventListener

接口方法

方法继承 (Methods Inherited)

该类从以下接口继承方法 -

java.awt.event.EventListener

FocusListener示例

使用您选择的任何编辑器创建以下Java程序，例如D:/ 》 SWING 》 com 》 xnip 》 gui 》

SwingListenerDemo.java

package cn.xnip.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.showFocusListenerDemo();
   }
   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 showFocusListenerDemo(){
      headerLabel.setText("Listener in action: FocusListener");      
      JButton okButton = new JButton("OK");
      JButton cancelButton = new JButton("Cancel");
      okButton.addFocusListener(new CustomFocusListener());  
      cancelButton.addFocusListener(new CustomFocusListener());  
      controlPanel.add(okButton);
      controlPanel.add(cancelButton);     
      mainFrame.setVisible(true);  
   }
   class CustomFocusListener implements FocusListener{
      public void focusGained(FocusEvent e) {
         statusLabel.setText(statusLabel.getText() 
            + e.getComponent().getClass().getSimpleName() + " gained focus. ");
      }
      public void focusLost(FocusEvent e) {
         statusLabel.setText(statusLabel.getText() 
            + e.getComponent().getClass().getSimpleName() + " lost focus. ");
      }
   }
}

使用命令提示符编译程序。 转到D:/ 》 SWING并键入以下命令。

D:\SWING>javac com\xnip\gui\SwingListenerDemo.java

如果没有错误发生，则表示编译成功。 使用以下命令运行该程序。

D:\SWING>java cn.xnip.gui.SwingListenerDemo

验证以下输出。