Question

我正在编写一个应用程序，我想将我的登录表单设置为主表单的顶部，并始终位于主表单的顶部。我的意思是将其锁定在主表单前，直到登录表单关闭，这样用户可以在登录表单关闭后访问主表单。

Answer 1

您可以使用JDialog代替JFrame来制作模态框架。以下两个链接可以帮助您入门。

Answer 2

这遵循@Jabir概述的一般概念，但使用JOptionPane（使用模态对话框作为显示组件），因为它有许多方便的方法来完成我们需要的繁重工作。在普通的模态对话框中实现。

另一方面，对话框的选项窗格更通用。一旦我们开始思考“那很好，但我想把它改成......”就是直接使用JDialog的时候。选项窗格更难以在现有API提供的（多个）选项之外进行更改。

有关使用选项窗格的详细信息，请参阅How to Make Dialogs。

Login Form

import java.awt.*;
import javax.swing.*;

class LoginForm {

    private JPanel loginForm = new JPanel(new BorderLayout(5,5));
    private JTextField userID = new JTextField(12);
    private JPasswordField password = new JPasswordField(8);

    LoginForm() {
        initializeLoginForm();
    }

    /** 
     * Displays the log-in form inside a confirmation option pane. 
     * The result (OK/Cancel) of the option pane is returned for inspection.
     */
    public final int displayLoginForm(Component parent) {
        return JOptionPane.showConfirmDialog(
                parent, 
                loginForm, 
                "Log In", 
                JOptionPane.OK_CANCEL_OPTION, 
                JOptionPane.QUESTION_MESSAGE);
    }

    private final void initializeLoginForm() {
        JPanel labels = new JPanel(new GridLayout(0,1,5,5));
        loginForm.add(labels, BorderLayout.LINE_START);
        JPanel fields = new JPanel(new GridLayout(0,1,5,5));
        loginForm.add(fields);

        labels.add(new JLabel("User ID:", SwingConstants.TRAILING));
        labels.add(new JLabel("Password:", SwingConstants.TRAILING));

        JPanel userIdConstrain = new JPanel(
                new FlowLayout(FlowLayout.LEADING));
        userIdConstrain.add(userID);
        fields.add(userIdConstrain);

        JPanel passwordConstrain = new JPanel(
                new FlowLayout(FlowLayout.LEADING));
        passwordConstrain.add(password);
        fields.add(passwordConstrain);
    }

    public final String getUserID() {
        return userID.getText();
    }

    public final char[] getPasword() {
        return password.getPassword();
    }

    public static void main(String[] args) {
        Runnable r = new Runnable() {

            @Override
            public void run() {
                JLabel l = new JLabel("<html>"
                        + "<body style='width: 300px; height: 175px;>",
                        SwingConstants.CENTER);
                JFrame f = new JFrame("Secure Application");
                f.add(l);
                // Ensures JVM closes after frame(s) closed and
                // all non-daemon threads are finished
                f.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);
                // See http://stackoverflow.com/a/7143398/418556 for demo.
                f.setLocationByPlatform(true);

                // ensures the frame is the minimum size it needs to be
                // in order display the components within it
                f.pack();
                // ensures the minimum size is enforced.
                f.setMinimumSize(f.getSize());
                f.setVisible(true);

                LoginForm lif = new LoginForm();
                int result = lif.displayLoginForm(f);
                // do the approrpaite action for this result
                if (result==JOptionPane.OK_OPTION) {
                    l.setText("Welcome " + lif.getUserID());
                } else {
                    l.setText("This application requires authentication!");
                }
            }
        };
        // Swing GUIs should be created and updated on the EDT
        // http://docs.oracle.com/javase/tutorial/uiswing/concurrency
        SwingUtilities.invokeLater(r);
    }
}

JFrame锁定主窗体前面的登录表单

2 个答案: