好的开始我使用内置的jFrame创建者为netbeans创建了一个jframe。我添加了一个组合框（jcbClass），在屏幕右下方的模型选项中我添加了一些项目。因此，我双击组合框，根据之前组合框的选定项目向jcbClass添加更多项目。
但是当我运行程序并更改竞争组合框时，jcbClass中不再添加任何内容。我测试了jcb.addItem（“bob”）;在很多地方只是为了看它是否首先将它添加到组合框中而它没有。请帮助我对这个简单的任务非常沮丧。
回复：我做了很多研究，但不明白为什么它不起作用。
/*
Author: *****
Start Date: June 30 2016
End Date:
Info: Basic start for game and gets user input
*/
/**
*
* @author 8022307
*/
public class firstTimeStart extends javax.swing.JFrame {
/**
* Creates new form firstTimeStart
*/
public firstTimeStart() {
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() {
jLabel1 = new javax.swing.JLabel();
jtfNameInput = new javax.swing.JTextField();
jlName = new javax.swing.JLabel();
jcbRace = new javax.swing.JComboBox<>();
jlRace = new javax.swing.JLabel();
jlClass = new javax.swing.JLabel();
jcbClass = new javax.swing.JComboBox<>();
jbDone = new javax.swing.JButton();
jSeparator1 = new javax.swing.JSeparator();
jlTitleTwo = new javax.swing.JLabel();
jLabel2 = new javax.swing.JLabel();
jLabel3 = new javax.swing.JLabel();
jLabel4 = new javax.swing.JLabel();
jButton1 = new javax.swing.JButton();
setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE);
setTitle("Legends Of The Eclipse");
setName("jlTitle"); // NOI18N
setPreferredSize(new java.awt.Dimension(500, 500));
setResizable(false);
jLabel1.setFont(new java.awt.Font("Arial", 0, 24)); // NOI18N
jLabel1.setText("Legends Of The Eclipse");
jtfNameInput.setText("Name Goes Here");
jtfNameInput.addActionListener(new java.awt.event.ActionListener() {
public void actionPerformed(java.awt.event.ActionEvent evt) {
jtfNameInputActionPerformed(evt);
}
});
jlName.setText("Name");
jcbRace.setModel(new javax.swing.DefaultComboBoxModel<>(new String[] { "Elf", "Ork", "Human", "Dwarf", "Demon", "Angel" }));
jlRace.setText("Race");
jlClass.setText("Class");
jcbClass.setModel(new javax.swing.DefaultComboBoxModel<>(new String[] { "Ranger", "Assassin", "Rogue", "Archane Warrior", "Monk", "Wizard" }));
jcbClass.setName(""); // NOI18N
jcbClass.addActionListener(new java.awt.event.ActionListener() {
public void actionPerformed(java.awt.event.ActionEvent evt) {
jcbClassActionPerformed(evt);
}
});
jbDone.setText("Done");
jlTitleTwo.setFont(new java.awt.Font("Arial", 0, 18)); // NOI18N
jlTitleTwo.setText("Final Choice Check");
jLabel2.setText("jLabel2");
jLabel3.setText("jLabel3");
jLabel4.setText("jLabel4");
jButton1.setText("jButton1");
javax.swing.GroupLayout layout = new javax.swing.GroupLayout(getContentPane());
getContentPane().setLayout(layout);
layout.setHorizontalGroup(
layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
.addGroup(javax.swing.GroupLayout.Alignment.TRAILING, layout.createSequentialGroup()
.addContainerGap(javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)
.addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
.addGroup(javax.swing.GroupLayout.Alignment.TRAILING, layout.createSequentialGroup()
.addComponent(jLabel1)
.addGap(115, 115, 115))
.addGroup(javax.swing.GroupLayout.Alignment.TRAILING, layout.createSequentialGroup()
.addComponent(jlTitleTwo)
.addGap(176, 176, 176))))
.addGroup(layout.createSequentialGroup()
.addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
.addGroup(layout.createSequentialGroup()
.addGap(37, 37, 37)
.addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
.addGroup(layout.createSequentialGroup()
.addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
.addComponent(jlRace)
.addComponent(jlClass))
.addGap(58, 58, 58)
.addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING, false)
.addComponent(jtfNameInput)
.addComponent(jcbRace, 0, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)
.addComponent(jcbClass, 0, 120, Short.MAX_VALUE)))
.addComponent(jlName)))
.addGroup(layout.createSequentialGroup()
.addGap(38, 38, 38)
.addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
.addComponent(jLabel3)
.addComponent(jLabel2)
.addComponent(jLabel4))))
.addContainerGap(javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE))
.addGroup(javax.swing.GroupLayout.Alignment.TRAILING, layout.createSequentialGroup()
.addGap(0, 0, Short.MAX_VALUE)
.addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
.addComponent(jSeparator1, javax.swing.GroupLayout.Alignment.TRAILING, javax.swing.GroupLayout.PREFERRED_SIZE, 516, javax.swing.GroupLayout.PREFERRED_SIZE)
.addGroup(javax.swing.GroupLayout.Alignment.TRAILING, layout.createSequentialGroup()
.addComponent(jbDone)
.addGap(222, 222, 222))
.addGroup(javax.swing.GroupLayout.Alignment.TRAILING, layout.createSequentialGroup()
.addComponent(jButton1)
.addGap(220, 220, 220))))
);
layout.setVerticalGroup(
layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
.addGroup(layout.createSequentialGroup()
.addGap(20, 20, 20)
.addComponent(jLabel1)
.addGap(24, 24, 24)
.addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE)
.addComponent(jlName)
.addComponent(jtfNameInput, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE))
.addGap(18, 18, 18)
.addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE)
.addComponent(jcbRace, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE)
.addComponent(jlRace))
.addGap(18, 18, 18)
.addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE)
.addComponent(jlClass)
.addComponent(jcbClass, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE))
.addGap(18, 18, 18)
.addComponent(jbDone)
.addGap(18, 18, 18)
.addComponent(jSeparator1, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE)
.addGap(18, 18, 18)
.addComponent(jlTitleTwo)
.addGap(4, 4, 4)
.addComponent(jLabel2)
.addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
.addComponent(jLabel3)
.addGap(11, 11, 11)
.addComponent(jLabel4)
.addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.UNRELATED)
.addComponent(jButton1)
.addContainerGap(133, Short.MAX_VALUE))
);
pack();
}// </editor-fold>
private void jtfNameInputActionPerformed(java.awt.event.ActionEvent evt) {
}
private void jcbClassActionPerformed(java.awt.event.ActionEvent evt) {
if (jcbRace.getSelectedItem().toString().equals("Elf")){
jcbClass.addItem("bob");
}
}
/**
* @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(firstTimeStart.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
} catch (InstantiationException ex) {
java.util.logging.Logger.getLogger(firstTimeStart.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
} catch (IllegalAccessException ex) {
java.util.logging.Logger.getLogger(firstTimeStart.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
} catch (javax.swing.UnsupportedLookAndFeelException ex) {
java.util.logging.Logger.getLogger(firstTimeStart.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 firstTimeStart().setVisible(true);
}
});
}
// Variables declaration - do not modify
private javax.swing.JButton jButton1;
private javax.swing.JLabel jLabel1;
private javax.swing.JLabel jLabel2;
private javax.swing.JLabel jLabel3;
private javax.swing.JLabel jLabel4;
private javax.swing.JSeparator jSeparator1;
private javax.swing.JButton jbDone;
private javax.swing.JComboBox<String> jcbClass;
private javax.swing.JComboBox<String> jcbRace;
private javax.swing.JLabel jlClass;
private javax.swing.JLabel jlName;
private javax.swing.JLabel jlRace;
private javax.swing.JLabel jlTitleTwo;
private javax.swing.JTextField jtfNameInput;
// End of variables declaration
}