focuseventdemo.java

学习参考,java基本语法练习,包括一些常用的技巧

//焦点事件演示程序
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
public class FocusEventDemo extends JFrame implements FocusListener
{
	JButton btnOk,btnCancel;
	JTextField txtUser,txtPassword;
	JPanel pnlMain;
	JLabel lblUser,lblPassword,lblInfo;
	public FocusEventDemo()
	{
		pnlMain=new JPanel();
		pnlMain.setLayout(new GridLayout(4,2));
		lblUser=new JLabel("用户名:");
		txtUser=new JTextField();
		txtUser.addFocusListener(this);
		lblPassword=new JLabel("密码");
		txtPassword=new JTextField();
		txtPassword.addFocusListener(this);
		btnOk=new JButton("确定");
		btnOk.addFocusListener (this);
		btnCancel=new JButton("取消");
		btnCancel.addFocusListener (this);
		lblInfo=new JLabel("");
		lblInfo.setForeground(Color.RED);
		setContentPane(pnlMain);
		pnlMain.add(lblUser);
		pnlMain.add(txtUser);
		pnlMain.add(lblPassword);
		pnlMain.add(txtPassword);
		pnlMain.add(btnOk);
		pnlMain.add(btnCancel);
		pnlMain.add(lblInfo);
		setSize(250,150);
		setTitle("焦点事件演示");
		setVisible(true);
	}
	public void focusGained(FocusEvent fe)
	{
		if (fe.getSource()==txtUser)
			lblInfo.setText("请输入6-16位用户名");
		if (fe.getSource()==txtPassword)
			lblInfo.setText("请输入6-16位密码");
	}
	public void focusLost(FocusEvent fe)
	{
		if (fe.getSource()==btnOk)
			lblInfo.setText("确定按钮失去焦点!");
		if (fe.getSource()==txtUser)
			lblInfo.setText("");
		if (fe.getSource()==txtPassword)
			lblInfo.setText("");
	}
	public static void main(String []args)
	{
		FocusEventDemo fd=new FocusEventDemo();
	}
}