Java用swing实现登录窗口

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package JframeDemo;

import java.awt.Container;
import java.awt.Dimension;
import java.awt.FlowLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;

import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JOptionPane;
import javax.swing.JPasswordField;
import javax.swing.JTextField;
import javax.swing.WindowConstants;

public class LoginWindow extends JFrame{
	private static final long serialVersionUID = 1L;
	public LoginWindow() {
		Container c = getContentPane();
		//用户名,文本框组件
		JTextField jt = new JTextField();
		JLabel jl1 = new JLabel("用户名：");
		jt.setPreferredSize(new Dimension(300, 30));
		
		//密码,密码框组件
		JPasswordField jp = new JPasswordField();
		jp.setEchoChar('*');
		JLabel jl2 = new JLabel("密   码：");
		jp.setPreferredSize(new Dimension(300, 30));
		//登录按钮,提交按钮组件
		JButton jb1 = new JButton("登录");
	
		//重置
		JButton jb2 = new JButton("重置");
		jb2.addActionListener(new ActionListener() {
			
			@Override
			public void actionPerformed(ActionEvent e) {
				jt.setText("");
				jp.setText("");
				jt.requestFocus();
			}
		});
		//弹窗
		jb1.addActionListener(new ActionListener() {
			
			@Override
			public void actionPerformed(ActionEvent e) {
				
				if(jt.getText().trim().length()==0||new String(jp.getPassword()).trim().length()==0){
					JOptionPane.showMessageDialog(null, "用户名密码不允许为空");
					return;
					}
				if(jt.getText().trim().equals("mr") && new String(jp.getPassword()).trim().equals("mrsoft")) {
					JOptionPane.showMessageDialog(null, "登录成功");
				}else {
					JOptionPane.showMessageDialog(null, "用户名或密码错误");
				}
				
			}
		});
		
		//窗体
		setSize(320, 500);
		setLocationRelativeTo(null);
		setTitle("Login");
		setDefaultCloseOperation(WindowConstants.DISPOSE_ON_CLOSE);
		
		//流式布局
		setLayout(new FlowLayout());
		//窗体可见，写在add组件之后
        setVisible(true);
        c.add(jl1);
        c.add(jt);
        c.add(jl2);
        c.add(jp);
        c.add(jb1);
        c.add(jb2);
	}
	public static void main(String[] args) {
		new LoginWindow();
	}

}