Java GUI经典问题

img

package test;

import java.awt.BorderLayout;
import java.awt.Container;
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.JPanel;
import javax.swing.JPasswordField;
import javax.swing.JTextField;

public class FrameTest {

    private JFrame jFrame = new JFrame("登录");
    private Container c = jFrame.getContentPane();
    private JLabel a1 = new JLabel("用户名");
    private JTextField username = new JTextField();
    private JLabel a2 = new JLabel("密   码");
    private JPasswordField password = new JPasswordField();
    private JButton okbtn = new JButton("确定");
    private JButton cancelbtn = new JButton("退出");

    public FrameTest() {
        // 设置窗体的位置及大小
        jFrame.setBounds(600, 200, 300, 220);
        // 设置一层相当于桌布的东西
        c.setLayout(new BorderLayout());// 布局管理器
        // 设置按下右上角X号后关闭
        jFrame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        // 初始化--往窗体里放其他控件
        init();
        // 设置窗体可见
        jFrame.setVisible(true);
    }

    public void init() {

        /* 输入部分--Center */
        JPanel fieldPanel = new JPanel();
        fieldPanel.setLayout(null);
        a1.setBounds(50, 20, 50, 20);
        a2.setBounds(50, 60, 50, 20);
        fieldPanel.add(a1);
        fieldPanel.add(a2);
        username.setBounds(110, 20, 120, 20);
        password.setBounds(110, 60, 120, 20);
        fieldPanel.add(username);
        fieldPanel.add(password);
        c.add(fieldPanel, "Center");

        /* 按钮部分--South */
        JPanel buttonPanel = new JPanel();
        buttonPanel.setLayout(new FlowLayout());
        buttonPanel.add(okbtn);
        buttonPanel.add(cancelbtn);
        c.add(buttonPanel, "South");

        // 确认按下去获取
        okbtn.addActionListener(new ActionListener() {
            @Override
            public void actionPerformed(ActionEvent e) {
                String uname = username.getText();
                String pwd = String.valueOf(password.getPassword());
                if ("admin".equals(uname.trim()) && "123456".equals(pwd.trim())) {
                    JOptionPane.showMessageDialog(null, "登录成功", "登录提示", JOptionPane.INFORMATION_MESSAGE);
                } else {
                    username.setText("");
                    password.setText("");
                    JOptionPane.showMessageDialog(null, "登录失败", "登录提示", JOptionPane.ERROR_MESSAGE);
                }
            }
        });
        // 退出关闭窗口
        cancelbtn.addActionListener(new ActionListener() {
            @Override
            public void actionPerformed(ActionEvent e) {
                jFrame.dispose();
            }
        });
    }

    // 测试
    public static void main(String[] args) {
        new FrameTest();
    }
}

运行截图：
img