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。

类声明

以下是java.awt.event.FocusListener接口的声明:

public interface FocusListener
extends EventListener

接口方法 (Interface methods)

方法继承

该类继承以下接口的方法:

• 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:/ 》 AWT 》 com 》 iowiki 》 gui 》

package com.iowiki.gui;
import java.awt.*;
import java.awt.event.*;
public class AwtListenerDemo {
   private Frame mainFrame;
   private Label headerLabel;
   private Label statusLabel;
   private Panel controlPanel;
   public AwtListenerDemo(){
      prepareGUI();
   }
   public static void main(String[] args){
      AwtListenerDemo  awtListenerDemo = new AwtListenerDemo();  
      awtListenerDemo.showFocusListenerDemo();
   }
   private void prepareGUI(){
      mainFrame = new Frame("Java AWT Examples");
      mainFrame.setSize(400,400);
      mainFrame.setLayout(new GridLayout(3, 1));
      mainFrame.addWindowListener(new WindowAdapter() {
         public void windowClosing(WindowEvent windowEvent){
            System.exit(0);
         }        
      });    
      headerLabel = new Label();
      headerLabel.setAlignment(Label.CENTER);
      statusLabel = new Label();        
      statusLabel.setAlignment(Label.CENTER);
      statusLabel.setSize(350,100);
      controlPanel = new Panel();
      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");      
      Button okButton = new Button("OK");
      Button cancelButton = new Button("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:/ 》 AWT并键入以下命令。

D:\AWT>javac com\iowiki\gui\AwtListenerDemo.java

如果没有错误，那意味着编译成功。 使用以下命令运行程序。

D:\AWT>java com.iowiki.gui.AwtListenerDemo

验证以下输出