如何收听JCombobox选择事件

Question

当我选择JCombobox时我想要处理一个事件，当它被选中并显示下拉列表时，以及当下拉消失并取消选择JCombobox时处理事件。 / p>

注意，我不打算听取项目选择更改，但是当用户选择JCombobox并且UI弹出下拉列表时。

Answer 1

您想使用addPopupMenuListener，它使用以下界面：

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);
}