java - 如何监听 JCombobox 选择事件

Question

当我选择 JCombobox 时，我想在它被选中并显示下拉列表时处理一个事件，以及在下拉列表消失和 JCombobox 时处理该事件已取消选择。

请注意，我不是要监听项目选择更改，而是要监听当用户选择 JCombobox 并且 UI 弹出下拉列表时。

Answer 1

您想使用 addPopupMenuListener它使用以下接口(interface):

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);
}