import java.awt.*;
import javax.swing.*;
import java.awt.event.*;
public class FocusEventDemo extends JFrame implements FocusListener
{
	JButton btnOk,btnCancel;
	JLabel lblUserName,lblPassword,lblInfo;
	JTextField txtUserName;
	JPasswordField pwdPassword;
	JPanel pnlMain;
	public FocusEventDemo()
	{
		pnlMain=new JPanel(new GridLayout(3,2));
		lblUserName=new JLabel("用戶名:");
		txtUserName=new JTextField(8);
		txtUserName.addFocusListener(this);
		lblPassword=new JLabel("密 碼:");
		pwdPassword=new JPasswordField();
		pwdPassword.addFocusListener(this);
		btnOk=new JButton("確定");
		btnOk.addFocusListener(this);
		btnCancel=new JButton("取消");
		getContentPane().add(pnlMain,"Center");
		pnlMain.add(lblUserName);
		pnlMain.add(txtUserName);
		pnlMain.add(lblPassword);
		pnlMain.add(pwdPassword);
		pnlMain.add(btnOk);
		pnlMain.add(btnCancel);
		lblInfo=new JLabel("暫未獲得焦點");
		JPanel p2=new JPanel();
		getContentPane().add(p2,"South");
		p2.add(lblInfo);
		setTitle("鼠標事件演示");
		setVisible(true);
		setSize(250,180);
	}
	public void focusGained(FocusEvent fe)
	{
		Object o=fe.getSource();
		if(o==txtUserName)
		{
			lblInfo.setText("請輸入用戶名");
		}
		else if(o==pwdPassword)
		{
			lblInfo.setText("請輸入密碼");
		}
		else
			lblInfo.setText("暫未獲得焦點");
	}
	public void focusLost(FocusEvent fe)
	{
		Object o=fe.getSource();
		if(o==btnOk)
		{
			lblInfo.setText("確定按鈕失去焦點");
		}
		if(o==txtUserName)
			lblInfo.setText("");
		if(o==pwdPassword)
			lblInfo.setText("");
	}
	public static void main (String args[])
	{
		new FocusEventDemo();
	}
	
}