Java Swing 下拉列表

Question

我使用 JAVA Swing 创建了一个下拉列表。当我选择“跟踪 RCM 的状态:”时，我想在所选选项旁边创建另一个下拉列表。我应该使用 mouseactionlistener 代替吗？我试图完成类似的事情，当我单击菜单选项时，我可以在菜单选项类别下选择另一个列表。示例:http://smoothjazztampabay.com/wp-content/rockettheme/rt_metropolis_wp/menu-options/dropdownmenu.jpg

我尝试使用此代码但不能。

         if (state == ItemEvent.SELECTED)
        {
            ItemSelectable itemS = itemEvent.getItemSelectable();
            String cmd = selectedString(itemS);
            if ( cmd.equals("Keep track of status of RCM:"))
            {
                RCMCombo2.addItem(RCMCombo);
                selectionPanel.add(RCMCombo2);
            }

完整版代码如下:

    String [] RCM2 = {"Keep track of status of RCM:", "Add and activate RCM", "Remove RCM", 
     "Display the usage statistics for RCM", 
"Update capabilities of RCMs", "Show RCM used most frequently in the last n days",
"Display number of times the RCM was emptied in n hours"};


RCMCombo2 = new JComboBox(RCM2); 
RCMCombo2.addItemListener(itemListener);  
    RCMCombo2.setEditable(false);
    RCMCombo2.setBounds(10,10,10,30);

    //"Updates capabilities of RCM"); Get the location of RCM");

    selectionPanel.add(RCMCombo2);

ItemListener itemListener = new ItemListener() 
{
      public void itemStateChanged(ItemEvent itemEvent) 
      {
        int state = itemEvent.getStateChange();
        //System.out.println((state == ItemEvent.SELECTED) ? "Selected" : "Deselected");
        //System.out.println("Item: " + itemEvent.getItem());
        if (state == ItemEvent.SELECTED)
        {
            ItemSelectable itemS = itemEvent.getItemSelectable();
            String cmd = selectedString(itemS);
            if ( cmd.equals("Keep track of status of RCM:"))
            {
                RCMCombo2.addItem(RCMCombo2);
                selectionPanel.add(RCMCombo2);
            }

任何帮助将不胜感激。谢谢。

Answer 1

看起来您走在完全错误的轨道上。我认为您将 ItemListener 的使用与列表模型的设置混合在一起。看看这个guide to ComboBox - 它应该包含您需要的所有信息。