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来自「本压缩文档为《Java大学实用教程》（7-121-00959-5 电子工业出版社」· 代码 · 共 42 行

import java.awt.*; 
import java.awt.event.*;
import javax.swing.*;
class MyWindow extends JFrame implements FocusListener
{ 		
    JTextField text;
    JButton button;
    MyWindow(String s) 
    { 
      super(s);
      text=new JTextField(10);
      button=new JButton("按钮");
      text.requestFocusInWindow();
      Container con=getContentPane();
      con.setLayout(new FlowLayout());
      con.add(text); 
      con.add(button); 
      text.addFocusListener(this);
      button.addFocusListener(this);
      setBounds(100,100,150,150);
      setVisible(true);
      validate();
      setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    }
   public void focusGained(FocusEvent e)
    {
       JComponent com=(JComponent)e.getSource();
       com.setBackground(Color.blue);
    }
   public void focusLost(FocusEvent e)
    {
       JComponent com=(JComponent)e.getSource();
       com.setBackground(Color.red);
    }
}
class Example
{
    public static void main(String args[])
    { 
       MyWindow win=new MyWindow("窗口");
    }
}