Question

我正在使用netbeans GUI Builder！我已经创建了一个JFrame，并在其中放入了一个带有CardLayout的JPanel，以便在JPanel之间切换。 JFrame还附带一个菜单，附带不同的选项。现在我希望选项在用户登录之前显示为灰色。根据登录用户的提示，可以使用选项（参见图片）。

问题是我不知道如何在切换面板时获取用户登录的内容。登录面板知道在字段中输入的内容并知道登录是否正确。我尝试使用.getParent（）函数来更改Jframe中的变量，但这似乎不起作用。但是我如何从JPanel更改JMenu项目呢？（儿童父母关系见这张图片）

Answer 1

您好我已经开发了这个快速示例。（请关注mantain的方式并分享登录信息）。

正如@Jan建议的那样，这是MVC模式的粗略实现。你试图分开：模型：您正在使用的数据，以及用于服务和数据转换的组件层。视图：从用户接收数据的组件控制器：将视图与模型连接的方式您可以在此处获取更多信息的链接：The MVC pattern and SWING

用于获取登录的类：

package com.stackoverflow.login;

import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.Frame;
import java.awt.GridBagConstraints;
import java.awt.GridBagLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;

import javax.swing.JButton;
import javax.swing.JDialog;
import javax.swing.JLabel;
import javax.swing.JOptionPane;
import javax.swing.JPanel;
import javax.swing.JPasswordField;
import javax.swing.JTextField;
import javax.swing.border.LineBorder;

public class LoginDialog extends JDialog {

    private static final long serialVersionUID = 1L;

    // This is the class who will mantain the logged used information
    private User user;
    private JTextField tfUsername;
    private JPasswordField pfPassword;
    private JLabel lbUsername;
    private JLabel lbPassword;
    private JButton btnLogin;
    private JButton btnCancel;
    private boolean succeeded;

    public LoginDialog(Frame parent) {
        super(parent, "Login", true);
        //
        JPanel panel = new JPanel(new GridBagLayout());
        GridBagConstraints cs = new GridBagConstraints();

        cs.fill = GridBagConstraints.HORIZONTAL;

        lbUsername = new JLabel("Username: ");
        cs.gridx = 0;
        cs.gridy = 0;
        cs.gridwidth = 1;
        panel.add(lbUsername, cs);

        tfUsername = new JTextField(20);
        cs.gridx = 1;
        cs.gridy = 0;
        cs.gridwidth = 2;
        panel.add(tfUsername, cs);

        lbPassword = new JLabel("Password: ");
        cs.gridx = 0;
        cs.gridy = 1;
        cs.gridwidth = 1;
        panel.add(lbPassword, cs);

        pfPassword = new JPasswordField(20);
        cs.gridx = 1;
        cs.gridy = 1;
        cs.gridwidth = 2;
        panel.add(pfPassword, cs);
        panel.setBorder(new LineBorder(Color.GRAY));

        btnLogin = new JButton("Login");

        btnLogin.addActionListener(new ActionListener() {

            public void actionPerformed(ActionEvent e) {
                if (Login.authenticate(getUsername(), getPassword())) {
                    JOptionPane.showMessageDialog(LoginDialog.this,
                            "Hi " + getUsername() + "! You have successfully logged in.", "Login",
                            JOptionPane.INFORMATION_MESSAGE);
                    succeeded = true;
                    user = new User();
                    user.setPassword(getPassword());
                    user.setUsername(getUsername());
                    dispose();
                } else {
                    JOptionPane.showMessageDialog(LoginDialog.this, "Invalid username or password", "Login",
                            JOptionPane.ERROR_MESSAGE);
                    // reset username and password
                    tfUsername.setText("");
                    pfPassword.setText("");
                    succeeded = false;

                }
            }
        });
        btnCancel = new JButton("Cancel");
        btnCancel.addActionListener(new ActionListener() {

            public void actionPerformed(ActionEvent e) {
                dispose();
            }
        });
        JPanel bp = new JPanel();
        bp.add(btnLogin);
        bp.add(btnCancel);

        getContentPane().add(panel, BorderLayout.CENTER);
        getContentPane().add(bp, BorderLayout.PAGE_END);

        pack();
        setResizable(false);
        setLocationRelativeTo(parent);
    }

    public String getUsername() {
        return tfUsername.getText().trim();
    }

    public String getPassword() {
        return new String(pfPassword.getPassword());
    }

    public boolean isSucceeded() {
        return succeeded;
    }

    public User getUser() {
        return user;
    }

}

登录服务

package com.stackoverflow.login;
public class Login {

    public static boolean authenticate(String username, String password) {
        // hardcoded username and password
        if (username.equals("bob") && password.equals("secret")) {
            return true;
        }
        return false;
    }
}

保留用户信息的类： package com.stackoverflow.login;

/**
 * Class used to mantain the login information, it's just for educational
 * purpouses, for prod environment you must implement it in a secure way!!
 */
public class User {

    private String username;
    private String password;

    public String getUsername() {
        return username;
    }

    public void setUsername(String username) {
        this.username = username;
    }

    public String getPassword() {
        return password;
    }

    public void setPassword(String password) {
        this.password = password;
    }

}

运行程序的类

package com.stackoverflow.login;

import java.awt.Dialog;
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.JDialog;
import javax.swing.JFrame;
import javax.swing.JLabel;

/**
 * Run the program
 */
public class Main {
    public static void main(String[] args) {
        final JFrame frame = new JFrame("JDialog Demo");
        final JButton btnLogin = new JButton("Click to login");
        final JButton btnPanel = new JButton();

        LoginDialog loginDlg = new LoginDialog(frame);
        loginDlg.setVisible(true);
        // if logon successfully
        if (loginDlg.isSucceeded()) {
            btnLogin.setVisible(false);
            btnPanel.setText("Hi " + loginDlg.getUsername() + "! click to open new frame");
            frame.getContentPane().add(btnPanel);
        }

        btnPanel.addActionListener(new ActionListener() {

            @Override
            public void actionPerformed(ActionEvent e) {
                JLabel label = new JLabel("Logged user is: " + loginDlg.getUser().getUsername());
                JDialog mydialog = new JDialog();
                mydialog.setSize(new Dimension(400, 100));
                mydialog.setTitle("Another frame");
                mydialog.setModalityType(Dialog.ModalityType.APPLICATION_MODAL);
                mydialog.add(label);
                mydialog.setVisible(true);
            }
        });

        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setSize(300, 100);
        frame.setLayout(new FlowLayout());
        frame.getContentPane().add(btnLogin);
        frame.setVisible(true);
    }
}

Java登录用户

1 个答案: