接下来讲解如何使用wp-bootstrap navwalker实现带有WordPress主题的Bootstrap导航栏。 这个脚本非常流行，它可以整合你的导航栏，方便你创建子项目。
- 打开网址www.github.com/twittem/wp-bootstrap-navwalker ，选择V3-branch版本（适合bootstrap3.x），找到wp-bootstrap-navwalker.php文件，打开这个文件，将其内部代码全部复制（不要直接下载这个文件，下载的文件里包含一个网页脚本，会让站点后台定向到此文件的内部代码页）。代码:
<?php
/**
* WP Bootstrap Navwalker.
*
* @package WP-Bootstrap-Navwalker
*
* @wordpress-plugin
* Plugin Name: WP Bootstrap Navwalker
* Plugin URI: https://github.com/wp-bootstrap/wp-bootstrap-navwalker
* Description: A custom WordPress nav walker class to implement the Bootstrap 4 navigation style in a custom theme using the WordPress built in menu manager.
* Author: Edward McIntyre - @twittem, WP Bootstrap, William Patton - @pattonwebz
* Version: 4.3.0
* Author URI: https://github.com/wp-bootstrap
* GitHub Plugin URI: https://github.com/wp-bootstrap/wp-bootstrap-navwalker
* GitHub Branch: master
* License: GPL-3.0+
* License URI: http://www.gnu.org/licenses/gpl-3.0.txt
*/
/* Check if Class Exists. */
if ( ! class_exists( 'WP_Bootstrap_Navwalker' ) ) {
/**
* WP_Bootstrap_Navwalker class.
*
* @extends Walker_Nav_Menu
*/
class WP_Bootstrap_Navwalker extends Walker_Nav_Menu {
/**
* Starts the list before the elements are added.
*
* @since WP 3.0.0
*
* @see Walker_Nav_Menu::start_lvl()
*
* @param string $output Used to append additional content (passed by reference).
* @param int $depth Depth of menu item. Used for padding.
* @param stdClass $args An object of wp_nav_menu() arguments.
*/
public function start_lvl( &$output, $depth = 0, $args = array() ) {
if ( isset( $args->item_spacing ) && 'discard' === $args->item_spacing ) {
$t = '';
$n = '';
} else {
$t = "\t";
$n = "\n";
}
$indent = str_repeat( $t, $depth );
// Default class to add to the file.
$classes = array( 'dropdown-menu' );
/**
* Filters the CSS class(es) applied to a menu list element.
*
* @since WP 4.8.0
*
* @param array $classes The CSS classes that are applied to the menu `<ul>` element.
* @param stdClass $args An object of `wp_nav_menu()` arguments.
* @param int $depth Depth of menu item. Used for padding.
*/
$class_names = join( ' ', apply_filters( 'nav_menu_submenu_css_class', $classes, $args, $depth ) );
$class_names = $class_names ? ' class="' . esc_attr( $class_names ) . '"' : '';
/**
* The `.dropdown-menu` container needs to have a labelledby
* attribute which points to it's trigger link.
*
* Form a string for the labelledby attribute from the the latest
* link with an id that was added to the $output.
*/
$labelledby = '';
// find all links with an id in the output.
preg_match_all( '/(<a.*?id=\"|\')(.*?)\"|\'.*?>/im', $output, $matches );
// with pointer at end of array check if we got an ID match.
if ( end( $matches[2] ) ) {
// build a string to use as aria-labelledby.
$labelledby = 'aria-labelledby="' . esc_attr( end( $matches[2] ) ) . '"';
}
$output .= "{$n}{$indent}<ul$class_names $labelledby role=\"menu\">{$n}";
}
/**
* Starts the element output.
*
* @since WP 3.0.0
* @since WP 4.4.0 The {@see 'nav_menu_item_args'} filter was added.
*
* @see Walker_Nav_Menu::start_el()
*
* @param string $output Used to append additional content (passed by reference).
* @param WP_Post $item Menu item data object.
* @param int $depth Depth of menu item. Used for padding.
* @param stdClass $args An object of wp_nav_menu() arguments.
* @param int $id Current item ID.
*/
public function start_el( &$output, $item, $depth = 0, $args = array(), $id = 0 ) {
if ( isset( $args->item_spacing ) && 'discard' === $args->item_spacing ) {
$t = '';
$n = '';
} else {
$t = "\t";
$n = "\n";
}
$indent = ( $depth ) ? str_repeat( $t, $depth ) : '';
$classes = empty( $item->classes ) ? array() : (array) $item->classes;
// Initialize some holder variables to store specially handled item
// wrappers and icons.
$linkmod_classes = array();
$icon_classes = array();
/**
* Get an updated $classes array without linkmod or icon classes.
*
* NOTE: linkmod and icon class arrays are passed by reference and
* are maybe modified before being used later in this function.
*/
$classes = self::separate_linkmods_and_icons_from_classes( $classes, $linkmod_classes, $icon_classes, $depth );
// Join any icon classes plucked from $classes into a string.
$icon_class_string = join( ' ', $icon_classes );
/**
* Filters the arguments for a single nav menu item.
*
* WP 4.4.0
*
* @param stdClass $args An object of wp_nav_menu() arguments.
* @param WP_Post $item Menu item data object.
* @param int $depth Depth of menu item. Used for padding.
*/
$args = apply_filters( 'nav_menu_item_args', $args, $item, $depth );
// Add .dropdown or .active classes where they are needed.
if ( isset( $args->has_children ) && $args->has_children ) {
$classes[] = 'dropdown';
}
if ( in_array( 'current-menu-item', $classes, true ) || in_array( 'current-menu-parent', $classes, true ) ) {
$classes[] = 'active';
}
// Add some additional default classes to the item.
$classes[] = 'menu-item-' . $item->ID;
$classes[] = 'nav-item';
// Allow filtering the classes.
$classes = apply_filters( 'nav_menu_css_class', array_filter( $classes ), $item, $args, $depth );
// Form a string of classes in format: class="class_names".
$class_names = join( ' ', $classes );
$class_names = $class_names ? ' class="' . esc_attr( $class_names ) . '"' : '';
/**
* Filters the ID applied to a menu item's list item element.
*
* @since WP 3.0.1
* @since WP 4.1.0 The `$depth` parameter was added.
*
* @param string $menu_id The ID that is applied to the menu item's `<li>` element.
* @param WP_Post $item The current menu item.
* @param stdClass $args An object of wp_nav_menu() arguments.
* @param int $depth Depth of menu item. Used for padding.
*/
$id = apply_filters( 'nav_menu_item_id', 'menu-item-' . $item->ID, $item, $args, $depth );
$id = $id ? ' id="' . esc_attr( $id ) . '"' : '';
$output .= $indent . '<li itemscope="itemscope" itemtype="https://www.schema.org/SiteNavigationElement"' . $id . $class_names . '>';
// initialize array for holding the $atts for the link item.
$atts = array();
// Set title from item to the $atts array - if title is empty then
// default to item title.
if ( empty( $item->attr_title ) ) {
$atts['title'] = ! empty( $item->title ) ? strip_tags( $item->title ) : '';
} else {
$atts['title'] = $item->attr_title;
}
$atts['target'] = ! empty( $item->target ) ? $item->target : '';
$atts['rel'] = ! empty( $item->xfn ) ? $item->xfn : '';
// If item has_children add atts to <a>.
if ( isset( $args->has_children ) && $args->has_children && 0 === $depth && $args->depth > 1 ) {
$atts['href'] = '#';
$atts['data-toggle'] = 'dropdown';
$atts['aria-haspopup'] = 'true';
$atts['aria-expanded'] = 'false';
$atts['class'] = 'dropdown-toggle nav-link';
$atts['id'] = 'menu-item-dropdown-' . $item->ID;
} else {
$atts['href'] = ! empty( $item->url ) ? $item->url : '#';
// Items in dropdowns use .dropdown-item instead of .nav-link.
if ( $depth > 0 ) {
$atts['class'] = 'dropdown-item';
} else {
$atts['class'] = 'nav-link';
}
}
$atts['aria-current'] = $item->current ? 'page' : '';
// update atts of this item based on any custom linkmod classes.
$atts = self::update_atts_for_linkmod_type( $atts, $linkmod_classes );
// Allow filtering of the $atts array before using it.
$atts = apply_filters( 'nav_menu_link_attributes', $atts, $item, $args, $depth );
// Build a string of html containing all the atts for the item.
$attributes = '';
foreach ( $atts as $attr => $value ) {
if ( ! empty( $value ) ) {
$value = ( 'href' === $attr ) ? esc_url( $value ) : esc_attr( $value );
$attributes .= ' ' . $attr . '="' . $value . '"';
}
}
/**
* Set a typeflag to easily test if this is a linkmod or not.
*/
$linkmod_type = self::get_linkmod_type( $linkmod_classes );
/**
* START appending the internal item contents to the output.
*/
$item_output = isset( $args->before ) ? $args->before : '';
/**
* This is the start of the internal nav item. Depending on what
* kind of linkmod we have we may need different wrapper elements.
*/
if ( '' !== $linkmod_type ) {
// is linkmod, output the required element opener.
$item_output .= self::linkmod_element_open( $linkmod_type, $attributes );
} else {
// With no link mod type set this must be a standard <a> tag.
$item_output .= '<a' . $attributes . '>';
}
/**
* Initiate empty icon var, then if we have a string containing any
* icon classes form the icon markup with an <i> element. This is
* output inside of the item before the $title (the link text).
*/
$icon_html = '';
if ( ! empty( $icon_class_string ) ) {
// append an <i> with the icon classes to what is output before links.
$icon_html = '<i class="' . esc_attr( $icon_class_string ) . '" aria-hidden="true"></i> ';
}
/** This filter is documented in wp-includes/post-template.php */
$title = apply_filters( 'the_title', esc_html( $item->title ), $item->ID );
/**
* Filters a menu item's title.
*
* @since WP 4.4.0
*
* @param string $title The menu item's title.
* @param WP_Post $item The current menu item.
* @param stdClass $args An object of wp_nav_menu() arguments.
* @param int $depth Depth of menu item. Used for padding.
*/
$title = apply_filters( 'nav_menu_item_title', $title, $item, $args, $depth );
/**
* If the .sr-only class was set apply to the nav items text only.
*/
if ( in_array( 'sr-only', $linkmod_classes, true ) ) {
$title = self::wrap_for_screen_reader( $title );
$keys_to_unset = array_keys( $linkmod_classes, 'sr-only', true );
foreach ( $keys_to_unset as $k ) {
unset( $linkmod_classes[ $k ] );
}
}
// Put the item contents into $output.
$item_output .= isset( $args->link_before ) ? $args->link_before . $icon_html . $title . $args->link_after : '';
/**
* This is the end of the internal nav item. We need to close the
* correct element depending on the type of link or link mod.
*/
if ( '' !== $linkmod_type ) {
// is linkmod, output the required closing element.
$item_output .= self::linkmod_element_close( $linkmod_type );
} else {
// With no link mod type set this must be a standard <a> tag.
$item_output .= '</a>';
}
$item_output .= isset( $args->after ) ? $args->after : '';
/**
* END appending the internal item contents to the output.
*/
$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. It is possible to set the
* max depth to include all depths, see walk() method.
*
* This method should not be called directly, use the walk() method instead.
*
* @since WP 2.5.0
*
* @see Walker::start_lvl()
*
* @param object $element Data object.
* @param array $children_elements List of elements to continue traversing (passed by reference).
* @param int $max_depth Max depth to traverse.
* @param int $depth Depth of current element.
* @param array $args An array of arguments.
* @param string $output Used to append additional content (passed by reference).
*/
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 menu 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( 'edit_theme_options' ) ) {
/* Get Arguments. */
$container = $args['container'];
$container_id = $args['container_id'];
$container_class = $args['container_class'];
$menu_class = $args['menu_class'];
$menu_id = $args['menu_id'];
// initialize var to store fallback html.
$fallback_output = '';
if ( $container ) {
$fallback_output .= '<' . esc_attr( $container );
if ( $container_id ) {
$fallback_output .= ' id="' . esc_attr( $container_id ) . '"';
}
if ( $container_class ) {
$fallback_output .= ' class="' . esc_attr( $container_class ) . '"';
}
$fallback_output .= '>';
}
$fallback_output .= '<ul';
if ( $menu_id ) {
$fallback_output .= ' id="' . esc_attr( $menu_id ) . '"'; }
if ( $menu_class ) {
$fallback_output .= ' class="' . esc_attr( $menu_class ) . '"'; }
$fallback_output .= '>';
$fallback_output .= '<li class="nav-item"><a href="' . esc_url( admin_url( 'nav-menus.php' ) ) . '" class="nav-link" title="' . esc_attr__( 'Add a menu', 'wp-bootstrap-navwalker' ) . '">' . esc_html__( 'Add a menu', 'wp-bootstrap-navwalker' ) . '</a></li>';
$fallback_output .= '</ul>';
if ( $container ) {
$fallback_output .= '</' . esc_attr( $container ) . '>';
}
// if $args has 'echo' key and it's true echo, otherwise return.
if ( array_key_exists( 'echo', $args ) && $args['echo'] ) {
echo $fallback_output; // WPCS: XSS OK.
} else {
return $fallback_output;
}
}
}
/**
* Find any custom linkmod or icon classes and store in their holder
* arrays then remove them from the main classes array.
*
* Supported linkmods: .disabled, .dropdown-header, .dropdown-divider, .sr-only
* Supported iconsets: Font Awesome 4/5, Glypicons
*
* NOTE: This accepts the linkmod and icon arrays by reference.
*
* @since 4.0.0
*
* @param array $classes an array of classes currently assigned to the item.
* @param array $linkmod_classes an array to hold linkmod classes.
* @param array $icon_classes an array to hold icon classes.
* @param integer $depth an integer holding current depth level.
*
* @return array $classes a maybe modified array of classnames.
*/
private function separate_linkmods_and_icons_from_classes( $classes, &$linkmod_classes, &$icon_classes, $depth ) {
// Loop through $classes array to find linkmod or icon classes.
foreach ( $classes as $key => $class ) {
// If any special classes are found, store the class in it's
// holder array and and unset the item from $classes.
if ( preg_match( '/^disabled|^sr-only/i', $class ) ) {
// Test for .disabled or .sr-only classes.
$linkmod_classes[] = $class;
unset( $classes[ $key ] );
} elseif ( preg_match( '/^dropdown-header|^dropdown-divider|^dropdown-item-text/i', $class ) && $depth > 0 ) {
// Test for .dropdown-header or .dropdown-divider and a
// depth greater than 0 - IE inside a dropdown.
$linkmod_classes[] = $class;
unset( $classes[ $key ] );
} elseif ( preg_match( '/^fa-(\S*)?|^fa(s|r|l|b)?(\s?)?$/i', $class ) ) {
// Font Awesome.
$icon_classes[] = $class;
unset( $classes[ $key ] );
} elseif ( preg_match( '/^glyphicon-(\S*)?|^glyphicon(\s?)$/i', $class ) ) {
// Glyphicons.
$icon_classes[] = $class;
unset( $classes[ $key ] );
}
}
return $classes;
}
/**
* Return a string containing a linkmod type and update $atts array
* accordingly depending on the decided.
*
* @since 4.0.0
*
* @param array $linkmod_classes array of any link modifier classes.
*
* @return string empty for default, a linkmod type string otherwise.
*/
private function get_linkmod_type( $linkmod_classes = array() ) {
$linkmod_type = '';
// Loop through array of linkmod classes to handle their $atts.
if ( ! empty( $linkmod_classes ) ) {
foreach ( $linkmod_classes as $link_class ) {
if ( ! empty( $link_class ) ) {
// check for special class types and set a flag for them.
if ( 'dropdown-header' === $link_class ) {
$linkmod_type = 'dropdown-header';
} elseif ( 'dropdown-divider' === $link_class ) {
$linkmod_type = 'dropdown-divider';
} elseif ( 'dropdown-item-text' === $link_class ) {
$linkmod_type = 'dropdown-item-text';
}
}
}
}
return $linkmod_type;
}
/**
* Update the attributes of a nav item depending on the limkmod classes.
*
* @since 4.0.0
*
* @param array $atts array of atts for the current link in nav item.
* @param array $linkmod_classes an array of classes that modify link or nav item behaviors or displays.
*
* @return array maybe updated array of attributes for item.
*/
private function update_atts_for_linkmod_type( $atts = array(), $linkmod_classes = array() ) {
if ( ! empty( $linkmod_classes ) ) {
foreach ( $linkmod_classes as $link_class ) {
if ( ! empty( $link_class ) ) {
// update $atts with a space and the extra classname...
// so long as it's not a sr-only class.
if ( 'sr-only' !== $link_class ) {
$atts['class'] .= ' ' . esc_attr( $link_class );
}
// check for special class types we need additional handling for.
if ( 'disabled' === $link_class ) {
// Convert link to '#' and unset open targets.
$atts['href'] = '#';
unset( $atts['target'] );
} elseif ( 'dropdown-header' === $link_class || 'dropdown-divider' === $link_class || 'dropdown-item-text' === $link_class ) {
// Store a type flag and unset href and target.
unset( $atts['href'] );
unset( $atts['target'] );
}
}
}
}
return $atts;
}
/**
* Wraps the passed text in a screen reader only class.
*
* @since 4.0.0
*
* @param string $text the string of text to be wrapped in a screen reader class.
* @return string the string wrapped in a span with the class.
*/
private function wrap_for_screen_reader( $text = '' ) {
if ( $text ) {
$text = '<span class="sr-only">' . $text . '</span>';
}
return $text;
}
/**
* Returns the correct opening element and attributes for a linkmod.
*
* @since 4.0.0
*
* @param string $linkmod_type a sting containing a linkmod type flag.
* @param string $attributes a string of attributes to add to the element.
*
* @return string a string with the openign tag for the element with attribibutes added.
*/
private function linkmod_element_open( $linkmod_type, $attributes = '' ) {
$output = '';
if ( 'dropdown-item-text' === $linkmod_type ) {
$output .= '<span class="dropdown-item-text"' . $attributes . '>';
} elseif ( 'dropdown-header' === $linkmod_type ) {
// For a header use a span with the .h6 class instead of a real
// header tag so that it doesn't confuse screen readers.
$output .= '<span class="dropdown-header h6"' . $attributes . '>';
} elseif ( 'dropdown-divider' === $linkmod_type ) {
// this is a divider.
$output .= '<div class="dropdown-divider"' . $attributes . '>';
}
return $output;
}
/**
* Return the correct closing tag for the linkmod element.
*
* @since 4.0.0
*
* @param string $linkmod_type a string containing a special linkmod type.
*
* @return string a string with the closing tag for this linkmod type.
*/
private function linkmod_element_close( $linkmod_type ) {
$output = '';
if ( 'dropdown-header' === $linkmod_type || 'dropdown-item-text' === $linkmod_type ) {
// For a header use a span with the .h6 class instead of a real
// header tag so that it doesn't confuse screen readers.
$output .= '</span>';
} elseif ( 'dropdown-divider' === $linkmod_type ) {
// this is a divider.
$output .= '</div>';
}
return $output;
}
}
}
在主题目录下创建一个同名文件，打开它将刚刚复制的代码粘贴进去，保存代码。
2. 打开functions.php文件，在顶部使用 require_once() 引入wp_bootstrap_navwalker.php文件
<?php
require_once('wp-bootstrap-navwalker.php');
function theme_setup(){
// Featured Image Support
add_theme_support('post-thumbnails');
}
add_action('after_setup_theme', 'theme_setup');3. 回到GitHub页面，我们现在将处理这些Usage。 我们想用导航栏内部的wp_nav_menu（）函数。 我们复制突出显示的部分
4. 进入导航栏所在的header文件，找到collapse类div，将刚刚复制的代码粘贴进去，如下所示：
<div class="collapse navbar-collapse" id="bs-example-navbar-collapse-1">
<?php
wp_nav_menu(
array('theme_location' => 'primary',
'depth' => 2,'container' => 'div',
'container_class' => 'collapse navbar-collapse',
'container_id' => 'bs-example-navbar-collapse-1',
'menu_class' => 'nav navbar-nav',
'fallback_cb' => 'WP_Bootstrap_Navwalker::fallback',
'walker' => new WP_Bootstrap_Navwalker(),));?>
<form class="navbar-form navbar-left"></form>
</div>
<!-- /.navbar-collapse -->5. 这些代码定义了一系列基本选项。 我们不需要所有这些，我们删掉几项，保存代码。 这是更新后的代码：
wp_nav_menu(
array('theme_location' => 'primary',
'depth' => 2,
'container' => false,
'menu_class' => 'nav navbar-nav',
'fallback_cb' => 'wp_bootstrap_navwalker::fallback',
'walker' => new wp_bootstrap_navwalker()));6. 回到 functions.php文件，在 theme_setup() 函数中添加代码注册导航菜单
// Nav Menus
register_nav_menus(array('primary' => __('Primary Menu')));}
add_action('after_setup_theme', 'theme_setup');我们在 register_nav_menus() 中传入一个数组，然后将primary设置为__（），然后可读名称是Primary Menu。
7.回到站点后台，外观功能下多了菜单选项
8. 现在创建一个名为“关于”的额外页面，然后单击发布。 让我们再创造一个名为“团队”的页面：
9. 打开菜单功能，点击“创建菜单”，确保 Primary Menu选项被勾选
10. 回到前端刷新页面，就可以看到刚刚添加的导航菜单了
11. 现在让我们测试一下“下拉菜单”功能。 我们把“示例页面”和“团队”放在“关于”页面的下级：
回到前端页面刷新，现在下拉菜单就出现了
学到这里你会发现实现导航栏非常容易。
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