我仍然渴望听到适用于此用例的操作，但如果没有其他结果，这里有一种更为暴力的方法：

// within My_Widget class definition
private static $metaboxes_added = false; // to ensure we don\'t add them more than once

// inside My_Widget class constructor
add_action( \'init\', array( $this, \'add_metaboxes\' ) );

// later, inside My_Widget class
public function add_metaboxes(){
    global $wp_registered_sidebars;

    if ( is_admin() && ! self::$metaboxes_added ){
        // These are the widgets grouped by sidebar
        $sidebars_widgets = wp_get_sidebars_widgets();

        foreach ( $sidebars_widgets as $sidebar_id => $widgets ) {
            if ( \'wp_inactive_widgets\' == $sidebar_id )
                continue;

            if ( isset( $wp_registered_sidebars[ $sidebar_id ] ) ) {
                if ( in_array( $this->id, $widgets ) ){ // $this is our Widget
                    self::$metaboxes_added = true; // In case we instantiate this sucker twice

                    add_action( \'add_meta_boxes\', array( $this, \'add_metabox_stuff\' ) );

                    break; // No need to go any further
                }
            }
        }
    }
}