未檢測到TextField和Password字段

需要幫助瞭解未檢測到textfield和password字段的原因？因此，這是我看到的錯誤（在txtUsername和PW紅線）未檢測到TextField和Password字段

private void btnLoginActionPerformed(java.awt.event.ActionEvent evt) {           
    if(txtUsername.getText().length()==0) { 
     JOptionPane.showMessageDialog(null, "Please fill up blank field/s!"); 
    } 
    else if(PW.getPassword().length==0) { 
     JOptionPane.showMessageDialog(null, "Please fill up blank field/s!"); 
    } 
    else { 
     String user = txtUsername.getText(); 
     char[] pass = PW.getPassword(); 
     String pwd = String.copyValueOf(pass); 
     if(validate_login(user,pwd)) 
      JOptionPane.showMessageDialog(null, "Correct Login Credentials!"); 
     else 
      JOptionPane.showMessageDialog(null,"Incorrect Login Credentials!"); 
    } 
}

之前，我把這個代碼：

private boolean validate_login (String username, String password) { 
    try { 
      Class.forName(".com.mysql.jdbc.Driver"); 
      Connection con= DriverManager.getConnection("jdbc:mysql://localhost:3306/logins" + "user=root&password="); 
      PreparedStatement pst = con.prepareStatement("Select * from admin where username=? and password=?"); 
      pst.setString(1, username); 
      pst.setString(2, password); 
      ResultSet rs = pst.executeQuery(); 
      if(rs.next()) { 
       return true; 
      } 
      else 
       return false; 
    } 
     catch(SQLException e) { 
     e.printStackTrace(); 
     return false; 
    }  

    } 
}

它沒有任何錯誤。現在它給了我很多錯誤，因爲我已經放置了這些代碼，但是這種方法本身並沒有錯誤。你能幫我麼？謝謝。

來源

2015-08-13 Ken Dogcio

首先，正確地捕捉您的異常並向我們顯示錯誤。 –

你在哪裏定義這些變量？把你所有的班級都放在這裏 – PeerNet

只有1個班級，那些是TextField，你可以直接打電話給他們，而無需宣佈正確？由於技術上他們已經被擺動聲明。 –

在您的validate_login方法中，存在不必要的大括號。刪除底部支架

來源

2015-08-13 10:06:09 PeerNet

其實你現在已經糾正了我的錯誤。 - 噢，上帝，我忘了檢查混雜支架有多重要 - 但是現在給我一個不同的錯誤。但是，謝謝！ –

根本不是。你可以選擇我的答案被接受。 – PeerNet

public class Login extends javax.swing.JFrame { 

public Login() { 
    initComponents(); 
} 
// <editor-fold defaultstate="collapsed" desc="Generated Code">       
private void initComponents() { 

    jPanel1 = new javax.swing.JPanel(); 
    jLabel1 = new javax.swing.JLabel(); 
    jLabel2 = new javax.swing.JLabel(); 
    txtUsername = new javax.swing.JTextField(); 
    PW = new javax.swing.JPasswordField(); 
    btnCancel = new javax.swing.JButton(); 
    btnLogin = new javax.swing.JButton(); 

    setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE); 

    jPanel1.setBackground(new java.awt.Color(0, 204, 153)); 
    jPanel1.setForeground(new java.awt.Color(255, 0, 0)); 

    jLabel1.setFont(new java.awt.Font("Trebuchet MS", 1, 12)); // NOI18N 
    jLabel1.setHorizontalAlignment(javax.swing.SwingConstants.CENTER); 
    jLabel1.setText("Password: "); 

    jLabel2.setFont(new java.awt.Font("Trebuchet MS", 1, 12)); // NOI18N 
    jLabel2.setHorizontalAlignment(javax.swing.SwingConstants.CENTER); 
    jLabel2.setText("Username: "); 

    txtUsername.setFont(new java.awt.Font("Trebuchet MS", 0, 12)); // NOI18N 
    txtUsername.addActionListener(new java.awt.event.ActionListener() { 
     public void actionPerformed(java.awt.event.ActionEvent evt) { 
      txtUsernameActionPerformed(evt); 
     } 
    }); 

    btnCancel.setFont(new java.awt.Font("Trebuchet MS", 1, 12)); // NOI18N 
    btnCancel.setText("Cancel"); 
    btnCancel.addActionListener(new java.awt.event.ActionListener() { 
     public void actionPerformed(java.awt.event.ActionEvent evt) { 
      btnCancelActionPerformed(evt); 
     } 
    }); 

    btnLogin.setFont(new java.awt.Font("Trebuchet MS", 1, 12)); // NOI18N 
    btnLogin.setText("Login"); 
    btnLogin.addActionListener(new java.awt.event.ActionListener() { 
     public void actionPerformed(java.awt.event.ActionEvent evt) { 
      btnLoginActionPerformed(evt); 
     } 
    }); 

    javax.swing.GroupLayout jPanel1Layout = new javax.swing.GroupLayout(jPanel1); 
    jPanel1.setLayout(jPanel1Layout); 
    jPanel1Layout.setHorizontalGroup(
     jPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING) 
     .addGroup(jPanel1Layout.createSequentialGroup() 
      .addGap(27, 27, 27) 
      .addGroup(jPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING) 
       .addGroup(jPanel1Layout.createSequentialGroup() 
        .addComponent(jLabel1, javax.swing.GroupLayout.PREFERRED_SIZE, 77, javax.swing.GroupLayout.PREFERRED_SIZE) 
        .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED) 
        .addGroup(jPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING, false) 
         .addGroup(jPanel1Layout.createSequentialGroup() 
          .addComponent(btnLogin) 
          .addGap(61, 61, 61) 
          .addComponent(btnCancel)) 
         .addComponent(PW))) 
       .addGroup(jPanel1Layout.createSequentialGroup() 
        .addComponent(jLabel2, javax.swing.GroupLayout.PREFERRED_SIZE, 77, javax.swing.GroupLayout.PREFERRED_SIZE) 
        .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED) 
        .addComponent(txtUsername))) 
      .addContainerGap(32, Short.MAX_VALUE)) 
    ); 
    jPanel1Layout.setVerticalGroup(
     jPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING) 
     .addGroup(javax.swing.GroupLayout.Alignment.TRAILING, jPanel1Layout.createSequentialGroup() 
      .addContainerGap(91, Short.MAX_VALUE) 
      .addGroup(jPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE) 
       .addComponent(jLabel2, javax.swing.GroupLayout.PREFERRED_SIZE, 37, javax.swing.GroupLayout.PREFERRED_SIZE) 
       .addComponent(txtUsername, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE)) 
      .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.UNRELATED) 
      .addGroup(jPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE) 
       .addComponent(jLabel1, javax.swing.GroupLayout.PREFERRED_SIZE, 37, javax.swing.GroupLayout.PREFERRED_SIZE) 
       .addComponent(PW, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE)) 
      .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.UNRELATED) 
      .addGroup(jPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE) 
       .addComponent(btnCancel) 
       .addComponent(btnLogin)) 
      .addGap(91, 91, 91)) 
    ); 

    javax.swing.GroupLayout layout = new javax.swing.GroupLayout(getContentPane()); 
    getContentPane().setLayout(layout); 
    layout.setHorizontalGroup(
     layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING) 
     .addComponent(jPanel1, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE) 
    ); 
    layout.setVerticalGroup(
     layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING) 
     .addComponent(jPanel1, javax.swing.GroupLayout.Alignment.TRAILING, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE) 
    ); 

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

private void btnLoginActionPerformed(java.awt.event.ActionEvent evt) {           
    if(txtUsername.getText().length()==0) { 
     JOptionPane.showMessageDialog(null, "Please fill up blank field/s!"); 
    } 
    else if(PW.getPassword().length==0) { 
     JOptionPane.showMessageDialog(null, "Please fill up blank field/s!"); 
    } 
    else { 
     String user = txtUsername.getText(); 
     char[] pass = PW.getPassword(); 
     String pwd = String.copyValueOf(pass); 
     if(validate_login(user,pwd)) 
      JOptionPane.showMessageDialog(null, "Correct Login Credentials!"); 
     else 
      JOptionPane.showMessageDialog(null,"Incorrect Login Credentials!"); 
    } 
}

來源

2015-08-13 10:09:31

'新的java.awt.Font（「Trebuchet MS」，1,12）'不可能在不是MS Windows的機器上工作。因爲'Trebuchet MS'字體不會被安裝。 –

未檢測到TextField和Password字段

回答

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