如何收听JCombobox选择事件

Question

当我选择JCombobox时，当它被选中并显示下拉列表时，我想处理一个事件，当下拉列表消失并取消选择JCombobox时，我也要处理该事件。

注意，我不想听到项目选择的变化，而是当用户选择JCombobox并且UI弹出下拉菜单时。

Answer 1

您想要使用addPopupMenuListener，它使用以下接口：

public interface PopupMenuListener extends EventListener {
    /**
     *  This method is called before the popup menu becomes visible 
     */
    void popupMenuWillBecomeVisible(PopupMenuEvent e);
    /**
     * This method is called before the popup menu becomes invisible
     * Note that a JPopupMenu can become invisible any time 
     */
    void popupMenuWillBecomeInvisible(PopupMenuEvent e);
    /**
     * This method is called when the popup menu is canceled
     */
    void popupMenuCanceled(PopupMenuEvent e);
}