java - 我应该如何让程序停止并等待某些事情？ java

Question

这里遇到问题，正在尝试创建数据库系统的登录名。我必须上课:UserLogManagerMainWindow 和 DatabaseConnectionFrame。我的程序是关于日志管理的。我想建立数据库连接:

UserLogManagerMainWindow 类有一个按钮“连接到数据库”，单击 DatabaseConnectionFrame 初始化并获取一个带有 jlabels 和 jtextfields 的框架，在输入我需要的所有内容后，我按“登录”按钮，在此之后我希望我的 UserLogManagerMainWindow类继续从连接的数据库中压入日志。

我已经编写了一些关于它应该是什么样子的代码:“关于我想说的内容的逻辑”

            connectToDatabaseBtn.addActionListener(new ActionListener() {

            @Override
            public void actionPerformed(ActionEvent e) {
                DatabaseConnectionFrame dcf = new DatabaseConnectionFrame();
                dcf.setVisible(true);

                if(dcf.answer == true) {
                    importButtons(menuBar);
                    setJMenuBar(menuBar);
                    try {
                        DatabaseComm.getColumnNamesToPanel(model, titles);
                        projects = DatabaseComm.AddLogsToArrayReturnProjectNames(events);
                        DatabaseComm.fillDataToPanel(model, events, titles, row);
                        DatabaseComm.resizeColumnWidth(table);
                    } catch (SQLException e1) {
                        // TODO Auto-generated catch block
                        e1.printStackTrace();
                    }

                }
                else {
                    System.out.println("not working");
                }

            }

        });

但是如果声明不起作用，我知道为什么。这就是为什么我要问如何让它发挥作用？更有可能的是，线程是关键，但目前并不擅长。有什么不用线程的技巧吗？如果线程是唯一的方法，我可以得到一些帮助吗？

提供以下任一 DatabaseConnectionFrame 类:

    package manager;

import java.awt.BorderLayout;
import java.awt.EventQueue;

import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.border.EmptyBorder;

import java.awt.GridBagLayout;
import javax.swing.JLabel;
import javax.swing.JOptionPane;

import java.awt.GridBagConstraints;
import java.awt.Insets;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.net.InetAddress;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;

import javax.swing.JTextField;
import javax.swing.JPasswordField;
import javax.swing.SwingConstants;
import javax.swing.JButton;

public class DatabaseConnectionFrame extends JFrame{

private JPanel contentPane;
private JTextField address;
private JPasswordField password;
private JTextField username;
private JButton btnLogin;
private JButton btnCancel;
private JLabel lblPort;
private JTextField port;

public boolean answer = false;

/**
 * Launch the application.
 */
public static void main(String[] args) {
    EventQueue.invokeLater(new Runnable() {
        public void run() {
            try {
                DatabaseConnectionFrame frame = new DatabaseConnectionFrame();
                frame.setVisible(true);
            } catch (Exception e) {
                e.printStackTrace();
            }
        }
    });
}

/**
 * Create the frame.
 */
public DatabaseConnectionFrame() {
    setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);
    setSize(450,250);
    contentPane = new JPanel();
    contentPane.setBorder(new EmptyBorder(5, 5, 5, 5));
    setContentPane(contentPane);
    GridBagLayout gbl_contentPane = new GridBagLayout();
    contentPane.setLayout(gbl_contentPane);

    JLabel lblDatabaseIpAddress = new JLabel("Database ip address:");
    GridBagConstraints gbc_lblDatabaseIpAddress = new GridBagConstraints();
    gbc_lblDatabaseIpAddress.anchor = GridBagConstraints.EAST;
    gbc_lblDatabaseIpAddress.insets = new Insets(0, 0, 5, 5);
    gbc_lblDatabaseIpAddress.gridx = 0;
    gbc_lblDatabaseIpAddress.gridy = 0;
    contentPane.add(lblDatabaseIpAddress, gbc_lblDatabaseIpAddress);

    address = new JTextField();
    GridBagConstraints gbc_textField = new GridBagConstraints();
    gbc_textField.insets = new Insets(0, 0, 5, 0);
    gbc_textField.fill = GridBagConstraints.HORIZONTAL;
    gbc_textField.gridx = 1;
    gbc_textField.gridy = 0;
    contentPane.add(address, gbc_textField);
    address.setColumns(10);

    lblPort = new JLabel("Port");
    GridBagConstraints gbc_lblPort = new GridBagConstraints();
    gbc_lblPort.anchor = GridBagConstraints.EAST;
    gbc_lblPort.insets = new Insets(0, 0, 5, 5);
    gbc_lblPort.gridx = 0;
    gbc_lblPort.gridy = 1;
    contentPane.add(lblPort, gbc_lblPort);

    port = new JTextField();
    GridBagConstraints gbc_textField1 = new GridBagConstraints();
    gbc_textField1.insets = new Insets(0, 0, 5, 0);
    gbc_textField1.fill = GridBagConstraints.HORIZONTAL;
    gbc_textField1.gridx = 1;
    gbc_textField1.gridy = 1;
    contentPane.add(port, gbc_textField1);
    port.setColumns(10);

    JLabel lblUsername = new JLabel("Username:");
    lblUsername.setHorizontalAlignment(SwingConstants.CENTER);
    GridBagConstraints gbc_lblUsername = new GridBagConstraints();
    gbc_lblUsername.anchor = GridBagConstraints.EAST;
    gbc_lblUsername.insets = new Insets(0, 0, 5, 5);
    gbc_lblUsername.gridx = 0;
    gbc_lblUsername.gridy = 2;
    contentPane.add(lblUsername, gbc_lblUsername);

    username = new JTextField();
    GridBagConstraints gbc_textField_1 = new GridBagConstraints();
    gbc_textField_1.insets = new Insets(0, 0, 5, 0);
    gbc_textField_1.fill = GridBagConstraints.HORIZONTAL;
    gbc_textField_1.gridx = 1;
    gbc_textField_1.gridy = 2;
    contentPane.add(username, gbc_textField_1);
    username.setColumns(10);

    JLabel lblPassword = new JLabel("Password");
    GridBagConstraints gbc_lblPassword = new GridBagConstraints();
    gbc_lblPassword.anchor = GridBagConstraints.EAST;
    gbc_lblPassword.insets = new Insets(0, 0, 5, 5);
    gbc_lblPassword.gridx = 0;
    gbc_lblPassword.gridy = 3;
    contentPane.add(lblPassword, gbc_lblPassword);

    password = new JPasswordField();
    GridBagConstraints gbc_passwordField = new GridBagConstraints();
    gbc_passwordField.insets = new Insets(0, 0, 5, 0);
    gbc_passwordField.fill = GridBagConstraints.HORIZONTAL;
    gbc_passwordField.gridx = 1;
    gbc_passwordField.gridy = 3;
    contentPane.add(password, gbc_passwordField);

    btnLogin = new JButton("Login");
    GridBagConstraints gbc_btnLogin = new GridBagConstraints();
    gbc_btnLogin.insets = new Insets(0, 0, 0, 5);
    gbc_btnLogin.gridx = 0;
    gbc_btnLogin.gridy = 4;
    contentPane.add(btnLogin, gbc_btnLogin);

    btnCancel = new JButton("Cancel");
    GridBagConstraints gbc_btnCancel = new GridBagConstraints();
    gbc_btnCancel.gridx = 1;
    gbc_btnCancel.gridy = 4;
    contentPane.add(btnCancel, gbc_btnCancel);




    btnCancel.addActionListener(new ActionListener() {

        @Override
        public void actionPerformed(ActionEvent e) {

            dispose();

        }

    });

    btnLogin.addActionListener(new ActionListener() {

        @Override
        public void actionPerformed(ActionEvent e) {

            String dbAddress = address.getText();
            String dbPort = port.getText();
            String dbUsername = username.getText();
            char[] dbPassword = password.getPassword();

            if( dbAddress.isEmpty() || dbPort.isEmpty() || dbUsername.isEmpty() || dbPassword.length == 0) {
                JOptionPane.showMessageDialog(getParent(),
                        "All fields have to be filled!");
            }
            else {
                if(databaseValidation(dbAddress, dbPort, dbUsername, dbPassword)) {
                    JOptionPane.showMessageDialog(getParent(),
                            "Connected!");
                    answer = true;
                    setVisible(false);
                }
                else {
                    JOptionPane.showMessageDialog(getParent(),
                            "There was error connecting to the database!");
                    answer = false;
                }
            }
            System.out.println(answer);

        }

    });
}

public boolean databaseValidation(String address, String port, String username, char[] password) {

    String pw = String.valueOf(password);
    System.out.println(pw);
    try {
        Connection con = DriverManager.getConnection("jdbc:mysql://" + address + ":" + port +  "/logctrl?user=" + username + "&password=" + pw );
    } catch (SQLException e) {
        System.out.println("Error connecting to database!");
        return false;
    }
    System.out.println("Connected");
    return true;

}

}

Answer 1

如果你想等待用户输入，你有两种选择，你可以创建自己的观察者模式，当状态以某种方式发生变化时可以在将来的某个时刻调用它，或者使用对话框，这将在对话框可见时阻止代码执行，并等待其关闭

参见How to use dialogs了解详情

import java.awt.Frame;
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.JFrame;
import javax.swing.JOptionPane;
import javax.swing.JPanel;
import javax.swing.SwingUtilities;

public class Test {

    public static void main(String[] args) {
        new Test();
    }

    public Test() {
        SwingUtilities.invokeLater(new Runnable() {
            @Override
            public void run() {
                JFrame frame = new JFrame("Test");
                frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
                frame.add(new TestPane());
                frame.pack();
                frame.setLocationRelativeTo(null);
                frame.setVisible(true);
            }
        });
    }

    public class TestPane extends JPanel {

        public TestPane() {
            setLayout(new GridBagLayout());
            JButton btn = new JButton("Show the dialog");
            add(btn);

            btn.addActionListener(new ActionListener() {
                @Override
                public void actionPerformed(ActionEvent e) {
                    JDialog dialog = new JDialog((Frame)SwingUtilities.getWindowAncestor(TestPane.this), "I'm in charge now", true);
                    JButton btn = new JButton("Waiting");
                    btn.addActionListener(new ActionListener() {
                        @Override
                        public void actionPerformed(ActionEvent e) {
                            dialog.dispose();
                        }
                    });
                    dialog.add(btn);
                    dialog.pack();
                    dialog.setLocationRelativeTo(TestPane.this);
                    dialog.setVisible(true);

                    JOptionPane.showMessageDialog(TestPane.this, "You won't see this till the dialog is closed");
                }
            });
        }

    }
}