从JMenuItem中删除

Question

好吧，所以我最终得到了JListMenu的东西，谢谢你们。但是，现在我正在尝试使它成为特定项目具有特定的命令。因此，与项目1类似，将无法右键单击取消，但项目2，项目3和项目4可以。看看我要去哪里？

因此，这里是我的代码至今：

import java.awt.*; 
import java.awt.event.MouseEvent; 
import java.awt.event.MouseListener; 
import java.awt.event.MouseAdapter; 
import java.awt.event.ActionEvent; 
import java.awt.event.ActionListener; 
import javax.swing.*; 
import javax.swing.border.*; 
import javax.swing.event.*; 

public class inv extends JApplet implements MouseListener 
{ 
    public JList listbox; 
    public JPopupMenu popup; 
    public JMenuItem item; 

    public void init() 
    { 
     ActionListener menuListener = new ActionListener() 
     { 
      public void actionPerformed(ActionEvent event) 
      { 
       String invAction = event.getActionCommand(); 


       int itemSelect = listbox.getSelectedIndex(); 
       Object actItem = listbox.getModel().getElementAt(itemSelect); 

       System.out.println("Popup menu item [" + invAction + "] [ " + actItem + " ] was pressed."); 
      } 
     }; 

     popup = new JPopupMenu(); 

     popup.add(item = new JMenuItem("Use")); 
     item.addActionListener(menuListener); 

     popup.add(item = new JMenuItem("Drop")); 
     item.addActionListener(menuListener); 

     popup.add(item = new JMenuItem("Cancel")); 
     item.addActionListener(menuListener); 



     String listData[] = 
     { 
      "Item 1","Item 2","Item 3","Item 4" 
     }; 

     listbox = new JList(listData); 
     listbox.addMouseListener(new MouseAdapter() 
     { 
      public void mousePressed(MouseEvent e) 
      { 
       if (SwingUtilities.isRightMouseButton(e)) 
       { 
        System.out.println("Row: " + getRow(e.getPoint())); 
        listbox.setSelectedIndex(getRow(e.getPoint())); 
       } 
      } 
     } 
     ); 

     listbox.setSelectionMode(ListSelectionModel.SINGLE_SELECTION); 
     add(listbox); 
     listbox.setVisible(true); 
     listbox.setFocusable(false); 


     listbox.addMouseListener(new MousePopupListener()); 
    } 

    class MousePopupListener extends MouseAdapter 
    { 
     public void mousePressed(MouseEvent e) 
     { 
      checkPopup(e); 
     } 

     public void mouseClicked(MouseEvent e) 
     { 
      checkPopup(e); 
     } 

     public void mouseReleased(MouseEvent e) 
     { 
      checkPopup(e); 
     } 

     private void checkPopup(MouseEvent e) 
     { 
      if (e.isPopupTrigger()) 
      { 

       int itemSelectx = listbox.getSelectedIndex(); 
       Object actItemx = listbox.getModel().getElementAt(itemSelectx); 
       System.out.println("You pressed on " + actItemx); 

       popup.show(inv.this, e.getX(), e.getY()); 
       popup.revalidate(); 
      } 
     } 
    } 

    private int getRow(Point point) 
    { 
     return listbox.locationToIndex(point); 
    } 

    public void mouseEntered(MouseEvent e) 
    { 
    } 

    public void mouseReleased(MouseEvent e) 
    { 
    } 

    public void mousePressed(MouseEvent e) 
    { 
    } 

    public void mouseClicked(MouseEvent e) 
    { 
    } 

    public void mouseExited(MouseEvent e) 
    { 
    } 
} 

和它的作品！我的意思是，右键点击，你会看到你在哪个项目列表上选择的选项。但是，右键单击菜单项时会有一个小小的警告标签。奇怪的。

Anwways，右下方System.out.println("You pressed on " + actItemx);我尝试添加此：

 if (actItemx == "Item 1") { 
      System.out.println("Removed cancel for " + actItemx); 
      popup.remove(2); // So upon right-click on Item 1, you won't see "Cancel" menu. 
     } 

和它似乎工作（但因为当时我要重新添加，嘿，这还没有完成）。但是，当我右键单击时，取消消失。像预期一样。呜！但后来我再次右键单击它，我得到了这个错误：

Exception in thread "AWT-EventQueue-1" java.lang.IllegalArgumentException: index 
greater than the number of items. 
     at javax.swing.JPopupMenu.remove(JPopupMenu.java:412) 
     at inv$MousePopupListener.checkPopup(inv.java:102) 
     at inv$MousePopupListener.mouseReleased(inv.java:88) 
     at java.awt.AWTEventMulticaster.mouseReleased(AWTEventMulticaster.java:2 
73) 
     at java.awt.Component.processMouseEvent(Component.java:6267) 
     at javax.swing.JComponent.processMouseEvent(JComponent.java:3267) 
     at java.awt.Component.processEvent(Component.java:6032) 
     at java.awt.Container.processEvent(Container.java:2041) 
     at java.awt.Component.dispatchEventImpl(Component.java:4630) 
     at java.awt.Container.dispatchEventImpl(Container.java:2099) 
     at java.awt.Component.dispatchEvent(Component.java:4460) 
     at java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:4577 
) 
     at java.awt.LightweightDispatcher.processMouseEvent(Container.java:4238) 

     at java.awt.LightweightDispatcher.dispatchEvent(Container.java:4168) 
     at java.awt.Container.dispatchEventImpl(Container.java:2085) 
     at java.awt.Component.dispatchEvent(Component.java:4460) 
     at java.awt.EventQueue.dispatchEvent(EventQueue.java:599) 
     at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThre 
ad.java:269) 
     at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread. 
java:184) 
     at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThre 
ad.java:174) 
     at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:169) 

     at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:161) 

     at java.awt.EventDispatchThread.run(EventDispatchThread.java:122) 

啊，回到绘图板。我究竟做错了什么？

Answer 1

更换

popup.remove(2); 

与

popup.remove(itemSelectx);