请在第一行非法开始表达 . 需要使它工作 . 谢谢

1 回答

• 0

  好的 . 我会尽力帮助你，不仅仅是你的问题，还有你编码风格的东西 .

  我会发布你的代码并评论我的解释 .

  package RegistrationSource;
  
  /*
   * You import stuff to simplify your Code and your typing work.
   * Example:
   * If you don't import javax.swing.*, then you must write it before every Class you want to use in this package.
   * But if you import javax.swing.*, then you don't need to write it anymore.
   * With that said, you can delete every "javax.swing." you see in your code, except for:
   * import javax.swing.*;
   * 
   * Also, your static JOptionPane imports are not necessarily.
   * You can just write: JOptionPanel.PLAIN_MESSAGE, because you only use it twice.
   * 
   * Keep in mind:
   * If you import javax.swing.*; it means you actually import every class in this package.
   * This is not as performing as importing every Class by itself, but I'll leave this to you.
   * Since you're using quite a lot of javax.swing it's fine this time.
   */
  
  import java.sql.Connection;
  import java.sql.DriverManager;
  import java.sql.PreparedStatement;
  import java.sql.ResultSet;
  import javax.swing.*;
  import javax.swing.border.*; // You need this, because border is also a package and not a class. You'll see down below
  
  import java.awt.Color; // added import
  import java.awt.Cursor; // added import
  import java.awt.Dimension; // added import
  import java.awt.EventQueue; // added import
  import java.awt.Font; // added import
  import java.awt.SystemColor; // added import
  import java.awt.event.ActionEvent; // added import
  import java.awt.event.ActionListener;
  
  public class Login extends JFrame {
  
      /*
       * Global Variables are declared just underneath the class declaration. So
       * whenever another programmer reads your code, they always see what they're using or what you were using.
       */
  
      private JButton blogin;
      private JButton jButton1;
      private JLabel jLabel1;
      private JLabel jLabel2;
      private JPanel jPanel1;
      private JSeparator jSeparator1;
      private JSeparator jSeparator2;
      private JSeparator jSeparator3;
      private JSeparator jSeparator4;
      private JPasswordField pfpassword;
      private JTextField tfusername;
  
      public Login() {
          initComponents();
      }
  
      @SuppressWarnings("unchecked")
      // <editor-fold defaultstate="collapsed" desc="Generated Code">
      private void initComponents() {
  
          jPanel1 = new JPanel();
          tfusername = new JTextField();
          pfpassword = new JPasswordField();
          jLabel1 = new JLabel();
          jLabel2 = new JLabel();
          blogin = new JButton();
          jButton1 = new JButton();
          jSeparator1 = new JSeparator();
          jSeparator2 = new JSeparator();
          jSeparator3 = new JSeparator();
          jSeparator4 = new JSeparator();
  
          setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
          setUndecorated(true);
  
          jPanel1.setBackground(SystemColor.activeCaption);
          jPanel1.setBorder(
                  BorderFactory.createTitledBorder(BorderFactory.createLineBorder(new Color(0, 0, 0)), "Welcome",
                          TitledBorder.LEFT, TitledBorder.DEFAULT_POSITION, new Font("Times New Roman", 1, 36))); // NOI18N
  
          /*
           * I'm talking about jpanel1.setBorder: Since I've imported the package
           * javax.swing.border.*; You can now just write TitledBorder.Something. If I
           * wouldn't import javax.swing.border.*, you must've written:
           * javax.swing.border.TitledBorder… But this isn't as readable as just
           * TitledBorder.
           */
  
          jLabel1.setText("Username:");
  
          jLabel2.setText("Password:");
  
          blogin.setText("Login");
          blogin.setCursor(new Cursor(Cursor.DEFAULT_CURSOR));
          blogin.addActionListener(new ActionListener() {
              public void actionPerformed(ActionEvent evt) {
                  bloginActionPerformed(evt);
              }
          });
  
          jButton1.setText("Cancel");
  
          jSeparator1.setForeground(new Color(255, 255, 255));
  
          jSeparator2.setForeground(new Color(255, 255, 255));
  
          jSeparator3.setForeground(new Color(255, 255, 255));
  
          jSeparator4.setForeground(new Color(255, 255, 255));
  
          GroupLayout jPanel1Layout = new GroupLayout(jPanel1);
          jPanel1.setLayout(jPanel1Layout);
          jPanel1Layout.setHorizontalGroup(jPanel1Layout.createParallelGroup(GroupLayout.Alignment.LEADING)
                  .addGroup(jPanel1Layout.createSequentialGroup().addGroup(jPanel1Layout
                          .createParallelGroup(GroupLayout.Alignment.LEADING)
                          .addGroup(jPanel1Layout.createSequentialGroup().addGap(58, 58, 58).addGroup(jPanel1Layout
                                  .createParallelGroup(GroupLayout.Alignment.TRAILING)
                                  .addGroup(jPanel1Layout.createSequentialGroup()
                                          .addGroup(jPanel1Layout.createParallelGroup(GroupLayout.Alignment.LEADING)
                                                  .addComponent(jLabel1).addComponent(jLabel2))
                                          .addGap(32, 32, 32)
                                          .addGroup(jPanel1Layout
                                                  .createParallelGroup(GroupLayout.Alignment.LEADING, false)
                                                  .addComponent(pfpassword).addComponent(tfusername,
                                                          GroupLayout.PREFERRED_SIZE, 185, GroupLayout.PREFERRED_SIZE)))
                                  .addGroup(jPanel1Layout.createSequentialGroup()
                                          .addComponent(blogin, GroupLayout.PREFERRED_SIZE, 96,
                                                  GroupLayout.PREFERRED_SIZE)
                                          .addGap(77, 77, 77).addComponent(jButton1, GroupLayout.PREFERRED_SIZE, 96,
                                                  GroupLayout.PREFERRED_SIZE))))
                          .addGroup(
                                  jPanel1Layout.createSequentialGroup().addGap(33, 33, 33).addGroup(
                                          jPanel1Layout.createParallelGroup(GroupLayout.Alignment.LEADING, false)
                                                  .addComponent(jSeparator1, GroupLayout.DEFAULT_SIZE, 311,
                                                          Short.MAX_VALUE)
                                                  .addComponent(jSeparator2))))
                          .addContainerGap(46, Short.MAX_VALUE))
                  .addComponent(jSeparator3).addComponent(jSeparator4));
          jPanel1Layout.setVerticalGroup(jPanel1Layout.createParallelGroup(GroupLayout.Alignment.LEADING)
                  .addGroup(jPanel1Layout.createSequentialGroup().addGap(17, 17, 17)
                          .addComponent(jSeparator1, GroupLayout.PREFERRED_SIZE, 10, GroupLayout.PREFERRED_SIZE)
                          .addPreferredGap(LayoutStyle.ComponentPlacement.UNRELATED)
                          .addGroup(jPanel1Layout.createParallelGroup(GroupLayout.Alignment.BASELINE)
                                  .addComponent(tfusername, GroupLayout.PREFERRED_SIZE, GroupLayout.DEFAULT_SIZE,
                                          GroupLayout.PREFERRED_SIZE)
                                  .addComponent(jLabel1))
                          .addGap(38, 38, 38)
                          .addGroup(jPanel1Layout.createParallelGroup(GroupLayout.Alignment.TRAILING)
                                  .addComponent(pfpassword, GroupLayout.PREFERRED_SIZE, GroupLayout.DEFAULT_SIZE,
                                          GroupLayout.PREFERRED_SIZE)
                                  .addComponent(jLabel2))
                          .addPreferredGap(LayoutStyle.ComponentPlacement.UNRELATED)
                          .addComponent(jSeparator2, GroupLayout.PREFERRED_SIZE, 10, GroupLayout.PREFERRED_SIZE)
                          .addPreferredGap(LayoutStyle.ComponentPlacement.RELATED, 42, Short.MAX_VALUE)
                          .addGroup(jPanel1Layout.createParallelGroup(GroupLayout.Alignment.BASELINE)
                                  .addComponent(blogin, GroupLayout.PREFERRED_SIZE, 33, GroupLayout.PREFERRED_SIZE)
                                  .addComponent(jButton1, GroupLayout.PREFERRED_SIZE, 33, GroupLayout.PREFERRED_SIZE))
                          .addGap(29, 29, 29)
                          .addComponent(jSeparator3, GroupLayout.PREFERRED_SIZE, 10, GroupLayout.PREFERRED_SIZE)
                          .addPreferredGap(LayoutStyle.ComponentPlacement.RELATED)
                          .addComponent(jSeparator4, GroupLayout.PREFERRED_SIZE, 5, GroupLayout.PREFERRED_SIZE)));
  
          GroupLayout layout = new GroupLayout(getContentPane());
          getContentPane().setLayout(layout);
          layout.setHorizontalGroup(layout.createParallelGroup(GroupLayout.Alignment.LEADING).addComponent(jPanel1,
                  GroupLayout.DEFAULT_SIZE, GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE));
          layout.setVerticalGroup(layout.createParallelGroup(GroupLayout.Alignment.LEADING).addComponent(jPanel1,
                  GroupLayout.Alignment.TRAILING, GroupLayout.DEFAULT_SIZE, GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE));
  
          setSize(new Dimension(400, 311));
          setLocationRelativeTo(null);
      }// </editor-fold>
  
      /*
       * Now here comes the real problem: You forgot to close the curly bracket for your method "bloginActionPerformed.
       */
  
      private void bloginActionPerformed(ActionEvent evt) {
          String sql = "select *from administrators where Username=? and Password=?";
          try {
              Class.forName("com.mysql.jdbc.Driver");
              Connection con = DriverManager.getConnection("jdbc:mysql://localhost/localdatabase", "root", "");
              PreparedStatement pst = con.prepareStatement(sql);
  
              pst.setString(1, tfusername.getText());
              pst.setString(2, new String(pfpassword.getPassword()));
  
              ResultSet rs = pst.executeQuery();
              if (rs.next()) {
                  JOptionPane.showMessageDialog(null, "Welcome " + tfusername.getText() + "!", "Successfull Log-in",
                          JOptionPane.INFORMATION_MESSAGE);
                  dispose();
                  registrationform registration = new registrationform();
                  registration.setVisible(true);
  
              } else {
                  JOptionPane.showMessageDialog(null, "Invalid username or password! ", "Invalid",
                          JOptionPane.ERROR_MESSAGE);
              }
  
          } catch (Exception e) {
              JOptionPane.showMessageDialog(null, e);
          }
  
          /**
           * @param args
           *            the command line arguments
           */
      } //bloginActionPerformed
  
      public static void main(String args[]) {
  
          loading splash = new loading();
          splash.setVisible(true);
          try {
              for (int i = 0; i <= 100; i++) {
                  Thread.sleep(40);
                  splash.loadnum.setText(Integer.toString(i) + "%");
                  splash.loadbar.setValue(i);
                  if (i == 100) {
                      splash.setVisible(false);
                      JOptionPane.showMessageDialog(null, "STUDENT RECORD SYSTEM", "S.Y. 2018 - 2019",
                              JOptionPane.PLAIN_MESSAGE);
                  }
              }
          } catch (Exception e) {
              JOptionPane.showMessageDialog(null, e);
          }
  
          /*
           * I've explained this already.
           * Lambdas are more readable and shorter.
           * They're very helpful, read about them. I recommend it.
           */
  
  //      EventQueue.invokeLater(new Runnable() {
  //
  //          public void run() {
  //              new Login().setVisible(true);
  //          }
  //      });
  
          EventQueue.invokeLater(() -> new Login().setVisible(true));
  
  
      } //main
  
  } // Class
  

  如果您只是复制此代码，它应该工作 . 不过，我建议阅读我的评论 .

  我将总结你的错误和我的风格建议：

  • 变量在类声明下声明

  • 你不明白导入东西的目的 . 我建议你玩简单的东西来理解它 .

  • 你可以使用一个lambda，这是更好的 .

  • 你的 class 名称没有改正，因为这会弄乱你的代码 . 你应该自己纠正它 .

  Now your main mistake: You simply forgot to close a curly bracket.

  如果您不关心我的其他建议和改进，您可以忽略我写的所有内容并关闭方法“bloginActionPerformed”的大括号 . 这应该工作 .

  玩得开心 .

  回复于 2024-04-27T12:53:23+08:00