如何在另一个类中引用字符串？

Question

我正在制作一个登录小程序以安装在我的无线hardrive上，并且当前正在为其构建框架，（每次我尝试将Strings声明为任何BUT final时，它都会显示一条错误，指出只允许使用final）我正在尝试使用String用户和String传递了在我的Skeleton类中找到的if语句：

package open;

import javax.swing.*;
import java.awt.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.JButton;
import javax.swing.JFrame;

public class Skeleton extends JFrame implements ActionListener{
    private static final long serialVersionUID = 1248L;

public static void addComponentsToPane(Container pane, Container container) {
    //Adding in text fields for login
    JButton b1 = new JButton("Login");
    final JTextField field2 = new JTextField(2);
    final JTextField field = new JTextField(1);

    //Creating Box Layout - Subject to change
    GroupLayout layout = new GroupLayout(pane);
    pane.setLayout(new BoxLayout(pane, BoxLayout.Y_AXIS));
    layout.setAutoCreateGaps(true);
    layout.setAutoCreateContainerGaps(true);

    //Setting alignments
    b1.setAlignmentX(Component.CENTER_ALIGNMENT);
    field.setAlignmentY(BOTTOM_ALIGNMENT);
    field2.setAlignmentY(BOTTOM_ALIGNMENT);
    b1.setAlignmentY(CENTER_ALIGNMENT);

    //Dimensions for User
    field.setMaximumSize(new Dimension(235, 20));
    field.setMinimumSize(new Dimension(235, 20));

    //Dimensions for Password
    field2.setMaximumSize(new Dimension(235, 20));
    field2.setMinimumSize(new Dimension(235, 20));

    //Dimensions for Button
    b1.setMaximumSize(new Dimension(100, 40));
    b1.setMinimumSize(new Dimension(100, 40));

    //Adding space between components
    container.add(Box.createRigidArea(new Dimension(275,20)));
    container.add(field);
    container.add(Box.createRigidArea(new Dimension(275,10)));
    container.add(field2);
    container.add(Box.createRigidArea(new Dimension(275,12)));
    container.add(b1);

    //Listen to the login button
    b1.addActionListener(new ActionListener(){
        public void actionPerformed(ActionEvent e)
        {
            String user = field.getText();
            String pass = field2.getText();
            System.out.println("Value: " + user + " " + pass);
        };
    });
}

    public static void createAndShowGUI() {

        JFrame frame = new JFrame("User Login");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setVisible(true);
        addComponentsToPane(frame.getContentPane(), frame);

        //Create a grey label
        JLabel greyLabel = new JLabel();
        greyLabel.setOpaque(true);
        greyLabel.setBackground(new Color(205, 209, 209));
        greyLabel.setPreferredSize(new Dimension(300, 400));

        //Adding the label to the pane
        frame.getContentPane().add(greyLabel, BorderLayout.CENTER);    

        //Display the window.
        frame.setSize(275, 175);
        frame.setVisible(true);
        }

    public static void closer(boolean close, JFrame frame){
        System.out.println(close);
        if(close == true){
            frame.setVisible(false);
            frame.dispose();
            }
        }
    public static void main(String[] args) {
        javax.swing.SwingUtilities.invokeLater(new Runnable() {
            public void run() {
                createAndShowGUI();
                }
            });
        }
public void actionPerformed(ActionEvent arg0) {
    }
}

在我的另一个类中，几乎没有任何东西，因为该类本身依赖于导入String变量

package password;

import open.Skeleton;
import refrence.Resources;

public class PasswordCompare    
{
public static void main(String[] args)
    {
    System.out.println(user);
    System.out.println(pass);
    }
}

Answer 1

我自己，我将上述GUI显示为模式JDialog，而不是JFrame，我将使用JPasswordField而不是第二个JTextField，并且将给我的类公开的getter方法，该方法将允许调用类查询其状态。它的领域，像

public String getUserName() {
    return userNameTextField.getText();
}

和

public char[] getPassword() {
   return passwordField.getPassword();
}

请注意，密码几乎永远不应被当作字符串处理，因为这样做会给您的应用程序带来严重的漏洞，使其他人更容易提取密码。

因此，作为模式对话框，调用代码会在对话框可见时停止，然后仅在对话框不再可见时重新启动，此时您可以使用上述方法查询对话框的状态，提取相关信息。

---

请注意，您的代码使用静态方法，这是您不希望执行的操作，因为这样做，您的类没有“状态”，因此查询JTextFields所保存的值将不起作用。

---

编辑
例如：

import java.awt.GridBagConstraints;
import java.awt.GridBagLayout;
import java.awt.Insets;

import javax.swing.*;

public class MySkeleton extends JPanel {
   private static final int COLUMN_COUNT = 10;
   private static final int I_GAP = 3;
   private JTextField userNameField = new JTextField();
   private JPasswordField passwordField = new JPasswordField();

   public MySkeleton() {
      super(new GridBagLayout());
      userNameField.setColumns(COLUMN_COUNT);
      passwordField.setColumns(COLUMN_COUNT);

      GridBagConstraints gbc = getGbc(0, 0, GridBagConstraints.BOTH);
      add(new JLabel("User Name:"), gbc);
      gbc = getGbc(1, 0, GridBagConstraints.HORIZONTAL);
      add(userNameField, gbc);
      gbc = getGbc(0, 1, GridBagConstraints.BOTH);
      add(new JLabel("Password:"), gbc);
      gbc = getGbc(1, 1, GridBagConstraints.HORIZONTAL);
      add(passwordField, gbc);
   }

   public static GridBagConstraints getGbc(int x, int y, int fill) {
      GridBagConstraints gbc = new GridBagConstraints();
      gbc.gridx = x;
      gbc.gridy = y;
      gbc.gridwidth = 1;
      gbc.gridheight = 1;
      gbc.weightx = 1.0;
      gbc.weighty = 1.0;
      gbc.insets = new Insets(I_GAP, I_GAP, I_GAP, I_GAP);
      gbc.fill = fill;

      return gbc;
   }

   public String getUserName() {
      return userNameField.getText();
   }

   public char[] getPassword() {
      return passwordField.getPassword();
   }
}

可以通过以下方法在另一类中进行测试：

public class MySkeletonTest {
   private static void createAndShowGui() {
      MySkeleton mainPanel = new MySkeleton();

      int input = JOptionPane.showConfirmDialog(null, mainPanel, "Login",
            JOptionPane.OK_CANCEL_OPTION, JOptionPane.PLAIN_MESSAGE);
      if (input == JOptionPane.OK_OPTION) {
         System.out.println("User Name: " + mainPanel.getUserName());

         // **** for testing purposes only. Never do this in a real app.
         System.out.println("Password:  " + new String(mainPanel.getPassword()));
      }
   }

   public static void main(String[] args) {
      SwingUtilities.invokeLater(new Runnable() {
         public void run() {
            createAndShowGui();
         }
      });
   }
}

Answer 2

您真的确定需要一门课来比较密码吗？ 这应该是您的ActionListener的代码。 另外，您甚至都没有在代码中实例化Skeleton ，因此无法访问这些字段。 如果您确实需要这样做，只需在Skeleton上定义一些吸气剂。

public String getPassword() {
   return field2.getText(); //you should really rename this field
}

public String getUser() {
   return field.getText(); //you should really rename this field
}