java - 从其他java类调用变量

标签 java swing netbeans modal-dialog non-static

我有这个登录屏幕类；

/*
 * To change this license header, choose License Headers in Project Properties.
 * To change this template file, choose Tools | Templates
 * and open the template in the editor.
 */

package program;
import java.sql.*;
import javax.swing.JOptionPane;

/**
 *
 * @author Lacrymae_Ev
 */
public class loginscreen extends javax.swing.JFrame {
    public String username;
    public String getUsername() {
       return username;
    }

    private String pwd;
    public String getPassword() {
       return pwd;
    }

    /**
     * Creates new form loginscreen
     */

    public loginscreen() {
        initComponents();
    }
    /**
     * This method is called from within the constructor to initialize the form.
     * WARNING: Do NOT modify this code. The content of this method is always
     * regenerated by the Form Editor.
     */
    @SuppressWarnings("unchecked")
    // <editor-fold defaultstate="collapsed" desc="Generated Code">                          
    private void initComponents() {

        Uname_Textfield = new javax.swing.JTextField();
        Password_PasswordField = new javax.swing.JPasswordField();
        Buton = new javax.swing.JButton();

        setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE);
        setResizable(false);

        Buton.setText("Bağlan");
        Buton.addActionListener(new java.awt.event.ActionListener() {
            public void actionPerformed(java.awt.event.ActionEvent evt) {
                ButonActionPerformed(evt);
            }
        });

        javax.swing.GroupLayout layout = new javax.swing.GroupLayout(getContentPane());
        getContentPane().setLayout(layout);
        layout.setHorizontalGroup(
            layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGroup(layout.createSequentialGroup()
                .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
                    .addGroup(layout.createSequentialGroup()
                        .addGap(10, 10, 10)
                        .addComponent(Uname_Textfield, javax.swing.GroupLayout.PREFERRED_SIZE, 150, javax.swing.GroupLayout.PREFERRED_SIZE))
                    .addGroup(layout.createSequentialGroup()
                        .addGap(10, 10, 10)
                        .addComponent(Password_PasswordField, javax.swing.GroupLayout.PREFERRED_SIZE, 150, javax.swing.GroupLayout.PREFERRED_SIZE))
                    .addGroup(layout.createSequentialGroup()
                        .addGap(54, 54, 54)
                        .addComponent(Buton)))
                .addContainerGap(javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE))
        );
        layout.setVerticalGroup(
            layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGroup(layout.createSequentialGroup()
                .addGap(11, 11, 11)
                .addComponent(Uname_Textfield, javax.swing.GroupLayout.PREFERRED_SIZE, 31, javax.swing.GroupLayout.PREFERRED_SIZE)
                .addGap(18, 18, 18)
                .addComponent(Password_PasswordField, javax.swing.GroupLayout.PREFERRED_SIZE, 30, javax.swing.GroupLayout.PREFERRED_SIZE)
                .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
                .addComponent(Buton, javax.swing.GroupLayout.PREFERRED_SIZE, 31, javax.swing.GroupLayout.PREFERRED_SIZE)
                .addContainerGap(javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE))
        );

        pack();
        setLocationRelativeTo(null);
    }// </editor-fold>                        


    private void ButonActionPerformed(java.awt.event.ActionEvent evt) {                                      
        // TODO add your handling code here:
       String username=Uname_Textfield.getText();
       String pwd= new String (Password_PasswordField.getPassword());
    try {  
        Class.forName("com.microsoft.sqlserver.jdbc.SQLServerDriver");
        String connectionUrl = "jdbc:sqlserver://192.168.100.100;" + "databaseName=ExampleDB;" + "user=" + username + ";" + "password=" + pwd + ";"; 
        Connection con = DriverManager.getConnection(connectionUrl);
        new ProgramPenceresi().setVisible(true);
        dispose();
        }
    catch (SQLException e) {
            JOptionPane.showMessageDialog(this, "Wrong username or passwordş!");   
        } 
    catch (ClassNotFoundException cE) {
            System.out.println("Class Not Found Exception: "+ cE.toString());
        }
    }                                     


    /**
     * @param args the command line arguments
     */
    public static void main(String args[]) {
        /* Set the Nimbus look and feel */
        //<editor-fold defaultstate="collapsed" desc=" Look and feel setting code (optional) ">
        /* If Nimbus (introduced in Java SE 6) is not available, stay with the default look and feel.
         * For details see http://download.oracle.com/javase/tutorial/uiswing/lookandfeel/plaf.html 
         */
        try {
            for (javax.swing.UIManager.LookAndFeelInfo info : javax.swing.UIManager.getInstalledLookAndFeels()) {
                if ("Nimbus".equals(info.getName())) {
                    javax.swing.UIManager.setLookAndFeel(info.getClassName());
                    break;
                }
            }
        } catch (ClassNotFoundException ex) {
            java.util.logging.Logger.getLogger(loginscreen.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
        } catch (InstantiationException ex) {
            java.util.logging.Logger.getLogger(loginscreen.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
        } catch (IllegalAccessException ex) {
            java.util.logging.Logger.getLogger(loginscreen.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
        } catch (javax.swing.UnsupportedLookAndFeelException ex) {
            java.util.logging.Logger.getLogger(loginscreen.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
        }
        //</editor-fold>

        /* Create and display the form */
        java.awt.EventQueue.invokeLater(new Runnable() {
            public void run() {
                new loginscreen().setVisible(true);
            }
        });
    }

    // Variables declaration - do not modify                     
    private javax.swing.JButton Buton;
    private javax.swing.JPasswordField Password_PasswordField;
    private javax.swing.JTextField Uname_Textfield;
    // End of variables declaration                   
}

我还有别的课；

/*
 * To change this license header, choose License Headers in Project Properties.
 * To change this template file, choose Tools | Templates
 * and open the template in the editor.
 */

package program;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.Statement;
import javax.swing.JOptionPane;
import net.proteanit.sql.DbUtils;

/**
 *
 * @author Lacrymae_Ev
 */
public class cagbas extends javax.swing.JFrame {
    loginscreen logindetails = new loginscreen ();
    String uname = logindetails.getUsername();
    String pass = logindetails.getPassword();
    private static ResultSet rs;
    private static Statement stmt;
    private static Connection con;
    private static final String query = "select 'AICB',sum(dur) as dur,sum(tot)as tot from exampletable with(nolock)\n" +
"where date between '2013-07-01 00:00:00.000' and '2013-07-01 23:59:59.999'\n" +
"and id='013'";
    /**
     * Creates new form cagbas
     */
    public cagbas() {
        initComponents();
    }

    /**
     * This method is called from within the constructor to initialize the form.
     * WARNING: Do NOT modify this code. The content of this method is always
     * regenerated by the Form Editor.
     */
    @SuppressWarnings("unchecked")
    // <editor-fold defaultstate="collapsed" desc="Generated Code">                          
    private void initComponents() {

        jScrollPane1 = new javax.swing.JScrollPane();
        jTable1 = new javax.swing.JTable();

        setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE);

        jTable1.setModel(DbUtils.resultSetToTableModel(rs));
        jScrollPane1.setViewportView(jTable1);

        javax.swing.GroupLayout layout = new javax.swing.GroupLayout(getContentPane());
        getContentPane().setLayout(layout);
        layout.setHorizontalGroup(
            layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGroup(layout.createSequentialGroup()
                .addContainerGap()
                .addComponent(jScrollPane1, javax.swing.GroupLayout.PREFERRED_SIZE, 375, javax.swing.GroupLayout.PREFERRED_SIZE)
                .addContainerGap(15, Short.MAX_VALUE))
        );
        layout.setVerticalGroup(
            layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGroup(layout.createSequentialGroup()
                .addContainerGap()
                .addComponent(jScrollPane1, javax.swing.GroupLayout.PREFERRED_SIZE, 275, javax.swing.GroupLayout.PREFERRED_SIZE)
                .addContainerGap(14, Short.MAX_VALUE))
        );

        pack();
    }// </editor-fold>                        

    /**
     * @param args the command line arguments
     */
    public static void main(String args[]) {
        /* Set the Nimbus look and feel */
        //<editor-fold defaultstate="collapsed" desc=" Look and feel setting code (optional) ">
        /* If Nimbus (introduced in Java SE 6) is not available, stay with the default look and feel.
         * For details see http://download.oracle.com/javase/tutorial/uiswing/lookandfeel/plaf.html 
         */
        try {
            for (javax.swing.UIManager.LookAndFeelInfo info : javax.swing.UIManager.getInstalledLookAndFeels()) {
                if ("Nimbus".equals(info.getName())) {
                    javax.swing.UIManager.setLookAndFeel(info.getClassName());
                    break;
                }
            }
        } catch (ClassNotFoundException ex) {
            java.util.logging.Logger.getLogger(cagbas.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
        } catch (InstantiationException ex) {
            java.util.logging.Logger.getLogger(cagbas.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
        } catch (IllegalAccessException ex) {
            java.util.logging.Logger.getLogger(cagbas.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
        } catch (javax.swing.UnsupportedLookAndFeelException ex) {
            java.util.logging.Logger.getLogger(cagbas.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
        }
        //</editor-fold>
 try
 {     
        Class.forName("com.microsoft.sqlserver.jdbc.SQLServerDriver");
        String connectionUrl = "jdbc:sqlserver://192.168.100.100;" + "databaseName=ExampleDB;" + "user=" + uname + ";" + "password=" + pass + ";"; 
        Connection con = DriverManager.getConnection(connectionUrl);
        stmt = con.createStatement();
        rs = stmt.executeQuery(query);
 }
 catch(Exception ex)
 {    
    JOptionPane.showMessageDialog(null, ex.toString());
 } 
        /* Create and display the form */
        java.awt.EventQueue.invokeLater(new Runnable() {
            public void run() {
                new cagbas().setVisible(true);
            }
        });
    }

    // Variables declaration - do not modify                     
    private javax.swing.JScrollPane jScrollPane1;
    private javax.swing.JTable jTable1;
    // End of variables declaration                   
}

但是我在 cagbas.java 中遇到了问题，因为当我开始这个类时，java 返回以下错误；

problem

我知道我不能在 main 方法中使用非静态对象。但是我如何使用第一个用户在我的程序中输入真实的用户名和密码？

最佳答案

我看到的一个问题是您的 LoginScreen 类是一个 JFrame，而 JFrame 的行为是在显示时不会停止来自调用代码的程序流，因此即使您可以从该对象中提取登录名和密码你以后的代码，你会过早地提取它，在用户有时间输入任何东西之前。

建议:

  • 最重要的是您正在尝试运行无法编译的代码。 永远不要这样做，因为这肯定会失败。相反，请在尝试运行程序之前解决编译问题。
  • 您的 LoginScreen 应该是模态 JDialog 而不是 JFrame。
  • 您首先显示此窗口以获得用户的输入。
  • 这里的关键点是，因为它是一个模态 JDialog，所以调用代码流会在对话框显示时停止。
  • 一旦对话框处理完毕并且不再可见，即用户输入数据或取消对话框后，调用代码就会恢复。
  • 那时，您可以通过调用 getter 方法从 LoginScreen 实例中获取登录用户名和密码(最好是后者以 char[] 形式获取)，并检查以确保它们不为空。即，LoginScreen 应该有一个 public String getUserName() 方法和一个 public char[] getPassword() 方法。
  • 调用代码现在可以在数据库中使用此信息。
  • 是的，请学习 Java 命名约定，并请遵守这些约定，让您的类名以大写字母开头，方法名和变量名以小写字母开头。这将使那些试图理解您的代码并帮助您(即这里的志愿者)做得更好的人更容易。

编辑

另请注意，JOptionPane 实际上只不过是一个模态 JDialog，它也可以用于您的目的，而且也很容易。例如，在下面的示例代码中，我创建了一个 InputForm JPanel，然后将该 JPanel 放入 JOptionPane 中:

import java.awt.GridBagConstraints;
import java.awt.GridBagLayout;
import java.awt.Insets;
import java.awt.event.ActionEvent;
import java.awt.event.KeyEvent;

import javax.swing.*;

@SuppressWarnings("serial")
public class MainFoo extends JPanel {
   private static final int COLUMNS = 10;
   private JTextField userNameField = new JTextField(COLUMNS);
   private JTextField passwordField = new JTextField(COLUMNS);
   private InputForm inputForm = new InputForm();

   public MainFoo() {
      add(new JLabel("User Name:"));
      add(userNameField);
      add(Box.createHorizontalStrut(15));
      add(new JLabel("Password:"));
      add(passwordField);
      add(new JButton(new LogInAction("Log in", KeyEvent.VK_L)));
   }

   private class LogInAction extends AbstractAction {
      public LogInAction(String name, int mnemonic) {
         super(name);
         putValue(MNEMONIC_KEY, mnemonic);
      }

      @Override
      public void actionPerformed(ActionEvent e) {
         int result = JOptionPane.showConfirmDialog(null, inputForm, "Input Form",
               JOptionPane.OK_CANCEL_OPTION, JOptionPane.PLAIN_MESSAGE);
         if (result == JOptionPane.OK_OPTION) {
            userNameField.setText(inputForm.getUserName());


            // ***** never do this! ***** 
            // Never change a password into a String.
            // This is for demo purposes only.
            passwordField.setText(new String(inputForm.getPassword())); 
         }
      }
   }

   private static void createAndShowGui() {
      JFrame frame = new JFrame("MainFoo");
      frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
      frame.getContentPane().add(new MainFoo());
      frame.pack();
      frame.setLocationRelativeTo(null);
      frame.setVisible(true);
   }

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


@SuppressWarnings("serial")
class InputForm extends JPanel {
   private static final int COLUMNS = 10;
   private static final int GAP = 3;
   private static final Insets LABEL_INSETS = new Insets(GAP, GAP, GAP, 15);
   private static final Insets TEXTFIELD_INSETS = new Insets(GAP, GAP, GAP, GAP);
   private JTextField userNameField = new JTextField(COLUMNS);
   private JPasswordField passwordField = new JPasswordField(COLUMNS);

   public InputForm() {
      setLayout(new GridBagLayout());
      addLabel("User Name:", 0);
      addTextField(userNameField, 0);

      addLabel("Password:", 1);
      addTextField(passwordField, 1);

   }

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

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


   private void addTextField(JTextField field, int row) {
      GridBagConstraints gbc = new GridBagConstraints();
      gbc.gridwidth = 1;
      gbc.gridheight = 1;
      gbc.gridx = 1;
      gbc.gridy = row;
      gbc.anchor = GridBagConstraints.EAST;
      gbc.fill = GridBagConstraints.HORIZONTAL;
      gbc.insets = TEXTFIELD_INSETS;
      gbc.weightx = 1.0;
      gbc.weighty = 1.0;
      add(field, gbc);
   }

   private void addLabel(String text, int row) {
      GridBagConstraints gbc = new GridBagConstraints();
      gbc.gridwidth = 1;
      gbc.gridheight = 1;
      gbc.gridx = 0;
      gbc.gridy = row;
      gbc.anchor = GridBagConstraints.WEST;
      gbc.fill = GridBagConstraints.BOTH;
      gbc.insets = LABEL_INSETS;
      gbc.weightx = 1.0;
      gbc.weighty = 1.0;
      add(new JLabel(text), gbc);
   }
}

关于java - 从其他java类调用变量，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/21461754/

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