WordPress输出Bootstrap导航栏结构的菜单例子

最近tennfy在用Bootstrap重写博客主题，由于之前没有用过Bootstrap，所以也是花了不少功夫来了解Bootstrap。Bootstrap提供了很完整的css样式布局，对于有一定前端基础的人来说真的非常方便。

利用Bootstrap做wordpress主题遇到的第一个问题就是输出Bootstrap导航栏结构的菜单，这样才能够利用Bootstrap提供的样式进行菜单的显示。本文就来介绍下如何实现wordpress输出Bootstrap的菜单结构。

Bootstrap导航栏结构

常见的Bootstrap导航栏为如下形式：

defaultnavbar_demo

其HTML结构为：

自定义wp_nav_menu函数

熟悉wordpress的朋友都知道，wordpress一般采用wp_nav_menu函数输出菜单，而通过该函数输出的菜单是得不到上述的html结构的。不过值得高兴的是，wp_nav_menu函数支持自定义输出html结构。

wordpress中wp_nav_menu函数的参数如下所示：

$defaults = array(
'theme_location' => '',
'menu' => '',
'container' => 'div',
'container_class' => '',
'container_id' => '',
'menu_class' => 'menu',
'menu_id' => '',
'echo' => true,
'fallback_cb' => 'wp_page_menu',
'before' => '',
'after' => '',
'link_before' => '',
'link_after' => '',
'items_wrap' => '

%3$s

',
'depth' => 0,
'walker' => ''
);

wp_nav_menu( $defaults );

?>

其中，我们需要修改的就是walker参数。

输出Bootstrap导航栏结构菜单

在header.php中，通过如下代码输出导航栏菜单：

上面代码中walker参数的值是一个类，所以接下来你需要添加这个类，在主题的functions.php文件中添加下面代码：

/**
* Class Name: wp_bootstrap_navwalker
* GitHub URI: https://github.com/twittem/wp-bootstrap-navwalker
* Description: A custom WordPress nav walker class to implement the Bootstrap 3 navigation style in a custom theme using the WordPress built in menu manager.
* Version: 2.0.4
* Author: Edward McIntyre - @twittem
* License: GPL-2.0+
* License URI: http://www.g***nu.org/licenses/gpl-2.0.txt
*/

class wp_bootstrap_navwalker extends Walker_Nav_Menu {

/**
* @see Walker::start_lvl()
* @since 3.0.0
*
* @param string $output Passed by reference. Used to append additional content.
* @param int $depth Depth of page. Used for padding.
*/
public function start_lvl( &$output, $depth = 0, $args = array() ) {
$indent = str_repeat( "t", $depth );
$output .= "n$indent

n";
}

/**
* @see Walker::start_el()
* @since 3.0.0
*
* @param string $output Passed by reference. Used to append additional content.
* @param object $item Menu item data object.
* @param int $depth Depth of menu item. Used for padding.
* @param int $current_page Menu item ID.
* @param object $args
*/
public function start_el( &$output, $item, $depth = 0, $args = array(), $id = 0 ) {
$indent = ( $depth ) ? str_repeat( "t", $depth ) : '';

/**
* Dividers, Headers or Disabled
* =============================
* Determine whether the item is a Divider, Header, Disabled or regular
* menu item. To prevent errors we use the strcasecmp() function to so a
* comparison that is not case sensitive. The strcasecmp() function returns
* a 0 if the strings are equal.
*/
if ( strcasecmp( $item->attr_title, 'divider' ) == 0 && $depth === 1 ) {
$output .= $indent . '
• ';
  } else if ( strcasecmp( $item->title, 'divider') == 0 && $depth === 1 ) {
  $output .= $indent . '
• ';
  } else if ( strcasecmp( $item->attr_title, 'dropdown-header') == 0 && $depth === 1 ) {
  $output .= $indent . '
• ' . esc_attr( $item->title );
  } else if ( strcasecmp($item->attr_title, 'disabled' ) == 0 ) {
  $output .= $indent . '
• ';
  } 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 . '
• ';
  
  $atts = array();
  $atts['title'] = ! empty( $item->title ) ? $item->title : '';
  $atts['target'] = ! empty( $item->target ) ? $item->target : '';
  $atts['rel'] = ! empty( $item->xfn ) ? $item->xfn : '';
  
  // If item has_children add atts to a.
  if ( $args->has_children && $depth === 0 ) {
  $atts['href'] = '#';
  $atts['data-toggle'] = 'dropdown';
  $atts['class'] = 'dropdown-toggle';
  $atts['aria-haspopup'] = 'true';
  } 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;
  
  /*
  * Glyphicons
  * ===========
  * Since the the menu item is NOT a Divider or Header we check the see
  * if there is a value in the attr_title property. If the attr_title
  * property is NOT null we apply it as the class name for the glyphicon.
  */
  if ( ! empty( $item->attr_title ) )
  $item_output .= '' : '';
  $item_output .= $args->after;
  
  $output .= apply_filters( 'walker_nav_menu_start_el', $item_output, $item, $depth, $args );
  }
  }
  
  /**
  * Traverse elements to create list from elements.
  *
  * Display one element if the element doesn't have any children otherwise,
  * display the element and its children. Will only traverse up to the max
  * depth and no ignore elements under that depth.
  *
  * This method shouldn't be called directly, use the walk() method instead.
  *
  * @see Walker::start_el()
  * @since 2.5.0
  *
  * @param object $element Data object
  * @param array $children_elements List of elements to continue traversing.
  * @param int $max_depth Max depth to traverse.
  * @param int $depth Depth of current element.
  * @param array $args
  * @param string $output Passed by reference. Used to append additional content.
  * @return null Null on failure with no changes to parameters.
  */
  public function display_element( $element, &$children_elements, $max_depth, $depth, $args, &$output ) {
  if ( ! $element )
  return;
  
  $id_field = $this->db_fields['id'];
  
  // Display this element.
  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 );
  }
  
  /**
  * Menu Fallback
  * =============
  * If this function is assigned to the wp_nav_menu's fallback_cb variable
  * and a manu has not been assigned to the theme location in the WordPress
  * menu manager the function with display nothing to a non-logged in user,
  * and will add a link to the WordPress menu manager if logged in as an admin.
  *
  * @param array $args passed from the wp_nav_menu function.
  *
  */
  public static function fallback( $args ) {
  if ( current_user_can( 'manage_options' ) ) {
  
  extract( $args );
  
  $fb_output = null;
  
  if ( $container ) {
  $fb_output = '
  if ( $container_id )
  $fb_output .= ' id="' . $container_id . '"';
  
  if ( $container_class )
  $fb_output .= ' class="' . $container_class . '"';
  
  $fb_output .= '>';
  }
  
  $fb_output .= '
  
  if ( $menu_id )
  $fb_output .= ' id="' . $menu_id . '"';
  
  if ( $menu_class )
  $fb_output .= ' class="' . $menu_class . '"';
  
  $fb_output .= '>';
  $fb_output .= '
• ';
  $fb_output .= '

';

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

echo $fb_output;
}
}
}