Java Swing文本域問題

Question

我使用Netbeans創建了一個GUI，它要求用戶在textfields和textareas輸入內容。 當我嘗試在其他類中使用它時，當我在其上使用getText方法時，在文本textfield中輸入的文本不會出現。 取而代之的是，只要使用getText方法，就會出現使用Netbeans中的編輯文本選項指定的文本textfield中顯示的文本。 問題與某種排序或順序有關嗎？ 因為我相信GUI中的文本是在用戶實際輸入之前被引用的。

public class GUI extends javax.swing.JFrame {

public GUI() {

    initComponents();
}
public void Grow(){
    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() {

    jTextField1 = new javax.swing.JTextField();
    jPanel1 = new javax.swing.JPanel();
    username = new javax.swing.JTextField();
    UsernameLabel = new javax.swing.JLabel();
    PasswordLabel = new javax.swing.JLabel();
    subject = new javax.swing.JTextField();
    SubjectLabel = new javax.swing.JLabel();
    jScrollPane1 = new javax.swing.JScrollPane();
    message = new javax.swing.JTextArea();
    jLabel1 = new javax.swing.JLabel();
    salutation = new javax.swing.JTextField();
    jLabel2 = new javax.swing.JLabel();
    sendbutton = new javax.swing.JButton();
    password = new javax.swing.JPasswordField();

    jTextField1.setText("jTextField1");

    setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE);

    jPanel1.setBackground(new java.awt.Color(204, 204, 255));
    jPanel1.setBorder(new        javax.swing.border.LineBorder(java.awt.SystemColor.controlDkShadow, 3, true));

    username.setText("Enter your text here");

    UsernameLabel.setFont(new java.awt.Font("Arial", 1, 13)); // NOI18N
    UsernameLabel.setForeground(new java.awt.Color(255, 51, 51));
    UsernameLabel.setText("Username");

    PasswordLabel.setFont(new java.awt.Font("Arial", 1, 13)); // NOI18N
    PasswordLabel.setForeground(new java.awt.Color(255, 51, 51));
    PasswordLabel.setText("Password");

    subject.setText("Enter your text here");
    subject.setCursor(new java.awt.Cursor(java.awt.Cursor.TEXT_CURSOR));
    subject.addActionListener(new java.awt.event.ActionListener() {
        public void actionPerformed(java.awt.event.ActionEvent evt) {
            subjectActionPerformed(evt);
        }
    });

    SubjectLabel.setFont(new java.awt.Font("Arial", 1, 13)); // NOI18N
    SubjectLabel.setForeground(new java.awt.Color(255, 51, 51));
    SubjectLabel.setText("Subject");

    message.setColumns(20);
    message.setRows(5);
    message.setText("Enter your text here");
    jScrollPane1.setViewportView(message);

    jLabel1.setFont(new java.awt.Font("Arial", 1, 13)); // NOI18N
    jLabel1.setForeground(new java.awt.Color(255, 51, 51));
    jLabel1.setText("Message");

    salutation.setText("Enter your text here");

    jLabel2.setFont(new java.awt.Font("Arial", 1, 13)); // NOI18N
    jLabel2.setForeground(new java.awt.Color(255, 51, 51));
    jLabel2.setText("Salutation");

    sendbutton.setForeground(new java.awt.Color(255, 51, 51));
    sendbutton.setText("Send");
    sendbutton.addActionListener(new java.awt.event.ActionListener() {
        public void actionPerformed(java.awt.event.ActionEvent evt) {
            sendbuttonActionPerformed(evt);
        }
    });

    password.setText("Enter your text here");

    javax.swing.GroupLayout jPanel1Layout = new javax.swing.GroupLayout(jPanel1);
    jPanel1.setLayout(jPanel1Layout);
    jPanel1Layout.setHorizontalGroup(
        jPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
        .addGroup(jPanel1Layout.createSequentialGroup()
            .addContainerGap()
            .addGroup(jPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
                .addComponent(jScrollPane1)
                .addGroup(jPanel1Layout.createSequentialGroup()
                    .addGroup(jPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
                        .addComponent(jLabel2)
                        .addComponent(SubjectLabel))
                    .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.UNRELATED)
                    .addGroup(jPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING, false)
                        .addComponent(salutation)
                        .addComponent(subject))
                    .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)
                    .addGroup(jPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
                        .addComponent(UsernameLabel, javax.swing.GroupLayout.Alignment.TRAILING)
                        .addComponent(PasswordLabel))
                    .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
                    .addGroup(jPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING, false)
                        .addComponent(username)
                        .addComponent(password))
                    .addGap(47, 47, 47))
                .addComponent(jLabel1)
                .addGroup(javax.swing.GroupLayout.Alignment.TRAILING, jPanel1Layout.createSequentialGroup()
                    .addGap(0, 0, Short.MAX_VALUE)
                    .addComponent(sendbutton)))
            .addContainerGap())
    );
    jPanel1Layout.setVerticalGroup(
        jPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
        .addGroup(jPanel1Layout.createSequentialGroup()
            .addContainerGap()
            .addGroup(jPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE)
                .addComponent(username, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE)
                .addComponent(UsernameLabel)
                .addComponent(subject, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE)
                .addComponent(SubjectLabel))
            .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
            .addGroup(jPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE)
                .addComponent(PasswordLabel)
                .addComponent(salutation, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE)
                .addComponent(jLabel2)
                .addComponent(password, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE))
            .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED, 20, Short.MAX_VALUE)
            .addComponent(jLabel1)
            .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
            .addComponent(jScrollPane1, javax.swing.GroupLayout.PREFERRED_SIZE, 185, javax.swing.GroupLayout.PREFERRED_SIZE)
            .addGap(11, 11, 11)
            .addComponent(sendbutton))
    );

    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.DEFAULT_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)
    );

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


private void subjectActionPerformed(java.awt.event.ActionEvent evt) {                                        
    // TODO add your handling code here:
}                                       

private void sendbuttonActionPerformed(java.awt.event.ActionEvent evt) {                                           
    // TODO add your handling code here:
    MMMMain object = new MMMMain();
    object.MassMail();

}                                          

/**
 * @param args the command line arguments
 */
public 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(GUI.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
    } catch (InstantiationException ex) {
        java.util.logging.Logger.getLogger(GUI.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
    } catch (IllegalAccessException ex) {
        java.util.logging.Logger.getLogger(GUI.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
    } catch (javax.swing.UnsupportedLookAndFeelException ex) {
        java.util.logging.Logger.getLogger(GUI.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 GUI().setVisible(true);
        }
    });
}

// Variables declaration - do not modify                     
private javax.swing.JLabel PasswordLabel;
private javax.swing.JLabel SubjectLabel;
private javax.swing.JLabel UsernameLabel;
private javax.swing.JLabel jLabel1;
private javax.swing.JLabel jLabel2;
private javax.swing.JPanel jPanel1;
private javax.swing.JScrollPane jScrollPane1;
private javax.swing.JTextField jTextField1;
public javax.swing.JTextArea message;
public javax.swing.JPasswordField password;
public javax.swing.JTextField salutation;
public javax.swing.JButton sendbutton;
public javax.swing.JTextField subject;
public javax.swing.JTextField username;
// End of variables declaration                   
}

Answer 1

問題與某種排序或順序有關嗎？ 因為我相信GUI中的文本是在用戶實際輸入之前被引用的。

無論您的代碼實際上沒有重現您的問題，Swing都可以在事件驅動的場景中工作。 這意味着如果要正確獲取文本字段的文本，則必須發生事件。 例如：

JTextField textField = new JTextField(20);
JFrame frame = new JFrame("Sample");
frame.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);
frame.getContentPane().add(textField);
frame.pack();
frame.setVisible(true);

System.out.println(textField.getText());

然后不會打印任何內容，因為getText()調用在用戶甚至有機會編寫任何內容之前發生。 但是如果你這樣做：

final JTextField textField = new JTextField(20);
textField.addActionListener(new ActionListener() {
    @Override
    public void actionPerformed(ActionEvent evt) {
        System.out.println(textField.getText());
    }
};

JFrame frame = new JFrame("Sample");
frame.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);
frame.getContentPane().add(textField);
frame.pack();
frame.setVisible(true);

然后，當用戶鍵入一些文本並在文本字段中按Enter鍵時，將打印文本。 這是因為觸發了一個ActionEvent ，並且文本字段附加了一個ActionListener ，它偵聽這些事件並做出響應。 您可以在Swing教程的“ 編寫事件監聽器”部分中閱讀更多相關信息。