Question

I’m struggling with update my item in JComboBox. When I load item from a file, the combobox display properly, however when I tried to add or remove item from combobox item, the combobox doesn’t update automatically, it still remain the same item instead. Here is my code
This is where I load the combobox item

ObjectInputStream input;
    try {
        // TODO add your handling code here:           
        JFileChooser openFileChooser = new JFileChooser();            
        openFileChooser.setCurrentDirectory(new File("."));
        if (openFileChooser.showOpenDialog(null) == JFileChooser.APPROVE_OPTION){
            input = new ObjectInputStream(new FileInputStream(openFileChooser.getSelectedFile()));
            diary = (Diary)input.readObject();
            jTextArea3.setText(diary.getUnitCollection().toString());
            input.close();
            //Load Unit Item
            for (Unit u: diary.getUnitCollection()){
                jComboBox8.addItem(u.getUnitName());
                jComboBox1.addItem(u.getUnitName());
            }
        }            
    } catch (ClassNotFoundException ex) {
        Logger.getLogger(GUI.class.getName()).log(Level.SEVERE, null, ex);
    } catch (IOException ex) {
        Logger.getLogger(GUI.class.getName()).log(Level.SEVERE, null, ex);
    }

This is button to remove item

 private void jButton7ActionPerformed(java.awt.event.ActionEvent evt) {                                         
    // TODO add your handling code here:
    for (int i = 0; i < diary.getUnitCollection().size(); i++){
            if (jComboBox8.getSelectedItem().equals(diary.getUnitCollection().get(i).getUnitName())){
                diary.getUnitCollection().remove(diary.getUnitCollection().get(i));
                jTextArea3.setText("The Unit " + jComboBox8.getSelectedItem()+ " has been removed successfully");                   
            }
        }
}             

edit: just fix style (code block)

Answer 1

You need to add and remove content via a model, check out http://docs.oracle.com/javase/7/docs/api/javax/swing/DefaultComboBoxModel.html