JPanel动态添加JLabel不显示的问题

Question

import javax.swing.JLabel;public class NewJFrame extends javax.swing.JFrame {    /**
     * Creates new form NewJFrame
     */
    public NewJFrame() {
        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() {        jPanel1 = new javax.swing.JPanel();
        jButton1 = new javax.swing.JButton();        setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE);        javax.swing.GroupLayout jPanel1Layout = new javax.swing.GroupLayout(jPanel1);
        jPanel1.setLayout(jPanel1Layout);
        jPanel1Layout.setHorizontalGroup(
            jPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGap(0, 138, Short.MAX_VALUE)
        );
        jPanel1Layout.setVerticalGroup(
            jPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGap(0, 155, Short.MAX_VALUE)
        );        jButton1.setText("jButton1");
        jButton1.addMouseListener(new java.awt.event.MouseAdapter() {
            public void mouseClicked(java.awt.event.MouseEvent evt) {
                jButton1MouseClicked(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(118, 118, 118)
                        .addComponent(jPanel1, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE))
                    .addGroup(layout.createSequentialGroup()
                        .addGap(158, 158, 158)
                        .addComponent(jButton1)))
                .addContainerGap(144, Short.MAX_VALUE))
        );
        layout.setVerticalGroup(
            layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGroup(javax.swing.GroupLayout.Alignment.TRAILING, layout.createSequentialGroup()
                .addContainerGap(40, Short.MAX_VALUE)
                .addComponent(jButton1)
                .addGap(38, 38, 38)
                .addComponent(jPanel1, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE)
                .addGap(44, 44, 44))
        );        pack();
    }// </editor-fold>                            private void jButton1MouseClicked(java.awt.event.MouseEvent evt) {                                      
        // TODO add your handling code here:
        for(int i =0;i<3;i++){
            jPanel1.add(new JLabel("列"+i));
            jPanel1.revalidate();
            jPanel1.repaint();
        }
    }                                         /**
     * @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(NewJFrame.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
        } catch (InstantiationException ex) {
            java.util.logging.Logger.getLogger(NewJFrame.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
        } catch (IllegalAccessException ex) {
            java.util.logging.Logger.getLogger(NewJFrame.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
        } catch (javax.swing.UnsupportedLookAndFeelException ex) {
            java.util.logging.Logger.getLogger(NewJFrame.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 NewJFrame().setVisible(true);
            }
        });
    }    // Variables declaration - do not modify                     
    private javax.swing.JButton jButton1;
    private javax.swing.JPanel jPanel1;
    // End of variables declaration                   
}真不知道犯了什么错误啊。。求解。。  界面是用netbeans控件生成的代码。难道是这问题么。swingJpanelJLabel

Answer 1

没人回答的原因：
1、Swing的应用场景不多，现在进行Swing开发的已经很少很少了，大家都不是很愿意再执行你的代码
2、你写的代码格式不错，但是有个非常非常大的弊端：没注释。你愿意看没注释的代码吗，即便是自己写的，过一周估计你自己都不想看了。所以你得加上注释。查找错误的话，你可以先多多注释掉暂时没用的代码，先从直接new出来的代码开始找。比如先写一个JLabel，然后写一个JPanel，放进去能不能加载？如果能，再一点点添加，如果不能，恭喜你直接就找到原因了。开发本身就是一点点来的过程，不会真的有谁一直到写完所有代码才执行。最后，希望你早点解决问题。

Answer 2

自己结贴吧 是想在Panel上动态添加label。  找到问题了。 GroupLayout的问题。Panel.add()没有用了就。换个Layout就好了。