如何使用 walker 在 Wordpress 中自定义 wp_nav_menu 输出？

Question

我想将 wp_nav_menu 的格式设置为引导程序。这是引导程序的代码：

<ul class="nav navbar-nav">
    <li class="active"><a href="#">Link <span class="sr-only">(current)</span></a></li>
    <li><a href="#">Link</a></li>
    <li class="dropdown">
      <a href="#" class="dropdown-toggle" data-toggle="dropdown" role="button" aria-expanded="false">Dropdown <span class="caret"></span></a>
      <ul class="dropdown-menu" role="menu">
        <li><a href="#">Action</a></li>
        <li><a href="#">Another action</a></li>
        <li><a href="#">Something else here</a></li>
        <li class="divider"></li>
        <li><a href="#">Separated link</a></li>
        <li class="divider"></li>
        <li><a href="#">One more separated link</a></li>
      </ul>
    </li>
  </ul>

我认为关键点是：

1. 当li项有子菜单时，添加类“dropdown”；

2. 这个 li 项的“a”子项应该具有属性 (class="dropdown-toggle" data-toggle="dropdown" role="button" aria-expanded="false")

3. 子菜单 ul 项应具有“下拉菜单”类

我知道我必须使用 Walker 来解决这个问题，但我不明白该怎么做。现在我可以使用下面的代码将类添加到子菜单 ul 项：

function start_lvl(&$output, $depth) {
$indent = str_repeat("\t", $depth);
$output .= "\n$indent<ul class=\"dropdown-menu\">\n"; }

我还能做什么？谢谢！

Answer 1

// please add this code in function.php


class wp_bootstrap_navwalker extends Walker_Nav_Menu {

    public function start_lvl( &$output, $depth = 0, $args = array() ) {
        $indent = str_repeat( "\t", $depth );
        $output .= "\n$indent<ul role=\"menu\" class=\" dropdown-menu\">\n";
    }

    public function start_el( &$output, $item, $depth = 0, $args = array(), $id = 0 ) {
        $indent = ( $depth ) ? str_repeat( "\t", $depth ) : '';


        if ( strcasecmp( $item->attr_title, 'divider' ) == 0 && $depth === 1 ) {
            $output .= $indent . '<li role="presentation" class="divider">';
        } else if ( strcasecmp( $item->title, 'divider') == 0 && $depth === 1 ) {
            $output .= $indent . '<li role="presentation" class="divider">';
        } else if ( strcasecmp( $item->attr_title, 'dropdown-header') == 0 && $depth === 1 ) {
            $output .= $indent . '<li role="presentation" class="dropdown-header">' . esc_attr( $item->title );
        } else if ( strcasecmp($item->attr_title, 'disabled' ) == 0 ) {
            $output .= $indent . '<li role="presentation" class="disabled"><a href="#">' . esc_attr( $item->title ) . '</a>';
        } else {

            $class_names = $value = '';

            $classes = empty( $item->classes ) ? array() : (array) $item->classes;
            $classes[] = 'menu-item-' . $item->ID;

            $class_names = join( ' ', apply_filters( 'nav_menu_css_class', array_filter( $classes ), $item, $args ) );

            if ( $args->has_children )
                $class_names .= ' dropdown';

            if ( in_array( 'current-menu-item', $classes ) )
                $class_names .= 'active';

            $class_names = $class_names ? ' class="' . esc_attr( $class_names ) . '"' : '';

            $id = apply_filters( 'nav_menu_item_id', 'menu-item-'. $item->ID, $item, $args );
            $id = $id ? ' id="' . esc_attr( $id ) . '"' : '';

            $output .= $indent . '<li' . $id . $value . $class_names .'>';

            $atts = array();
            $atts['title']  = ! empty( $item->title )   ? $item->title  : '';
            $atts['target'] = ! empty( $item->target )  ? $item->target : '';
            $atts['rel']    = ! empty( $item->xfn )     ? $item->xfn    : '';


            if ( $args->has_children && $depth === 0 ) {
                $atts['href']           = '#';
                $atts['data-toggle']    = 'dropdown';
                $atts['class']          = 'dropdown-toggle';
                $atts['role']           = 'button';
                $atts['aria-haspopup']  = 'true';
                $atts['aria-expanded']  = 'false';



            } else {
                $atts['href'] = ! empty( $item->url ) ? $item->url : '';
            }

            $atts = apply_filters( 'nav_menu_link_attributes', $atts, $item, $args );

            $attributes = '';
            foreach ( $atts as $attr => $value ) {
                if ( ! empty( $value ) ) {
                    $value = ( 'href' === $attr ) ? esc_url( $value ) : esc_attr( $value );
                    $attributes .= ' ' . $attr . '="' . $value . '"';
                }
            }

            $item_output = $args->before;


            if ( ! empty( $item->attr_title ) )
                $item_output .= '<a'. $attributes .'><span class="glyphicon ' . esc_attr( $item->attr_title ) . '"></span>&nbsp;';
            else
                $item_output .= '<a'. $attributes .'>';
            $item_output .='<span>';
            $item_output .= $args->link_before . apply_filters( 'the_title', $item->title, $item->ID ) . $args->link_after;
            //$item_output .= ( $args->has_children && 0 === $depth ) ? ' <span class="caret"></span></a>' : '</a>';
            $item_output .='</span>';
            $item_output .= ( $args->has_children && 0 === $depth ) ? ' </a>' : '</a>';
            $item_output .= $args->after;

            $output .= apply_filters( 'walker_nav_menu_start_el', $item_output, $item, $depth, $args );
        }
    }


    public function display_element( $element, &$children_elements, $max_depth, $depth, $args, &$output ) {
        if ( ! $element )
            return;

        $id_field = $this->db_fields['id'];


        if ( is_object( $args[0] ) )
           $args[0]->has_children = ! empty( $children_elements[ $element->$id_field ] );

        parent::display_element( $element, $children_elements, $max_depth, $depth, $args, $output );
    }


    public static function fallback( $args ) {
        if ( current_user_can( 'manage_options' ) ) {

            extract( $args );

            $fb_output = null;

            if ( $container ) {
                $fb_output = '<' . $container;

                if ( $container_id )
                    $fb_output .= ' id="' . $container_id . '"';

                if ( $container_class )
                    $fb_output .= ' class="' . $container_class . '"';

                $fb_output .= '>';
            }

            $fb_output .= '<ul';

            if ( $menu_id )
                $fb_output .= ' id="' . $menu_id . '"';

            if ( $menu_class )
                $fb_output .= ' class="' . $menu_class . '"';

            $fb_output .= '>';
            $fb_output .= '<li><a href="' . admin_url( 'nav-menus.php' ) . '">Add a menu</a></li>';
            $fb_output .= '</ul>';

            if ( $container )
                $fb_output .= '</' . $container . '>';

            echo $fb_output;
        }
    }
}


//output 

wp_nav_menu( array(
                'menu'              => 'Primary',
                'theme_location'    => 'Top primary menu',
                'depth'             => 2,
                'container'         => '',
                'container_class'   => '',
                'container_id'      => '',
                'menu_class'        => 'nav navbar-nav',
                'fallback_cb'       => 'wp_bootstrap_navwalker::fallback',
                'walker'            => new wp_bootstrap_navwalker())
                );

Answer 2

我已经通过使用来自互联网的 walker 文件解决了这个问题。 在“wp-bootstrap-navwalker-master”中搜索 walker 文件。