我在PSD和WordPress之间创建了一个主题，但主页上没有显示“下一步”-“上一步”按钮。

这是的代码single.php:

    <div id="primary" class="site-content">
        <div id="content" role="main">

            <?php while ( have_posts() ) : the_post(); ?>

                <?php get_template_part( \'content\', get_post_format() ); ?>

                <nav class="nav-single">

                    <h3 class="assistive-text"><?php _e( \'Post navigation\', \'aquaponicfamily\' ); ?></h3>
                    <span class="nav-previous"><?php previous_post_link( \'%link\', \'<span class="meta-nav">\' . _x( \'&larr;\', \'Previous post link\', \'aquaponicfamily\' ) . \'</span> %title\' ); ?></span>
                    <span class="nav-next"><?php next_post_link( \'%link\', \'%title <span class="meta-nav">\' . _x( \'&rarr;\', \'Next post link\', \'aquaponicfamily\' ) . \'</span>\' ); ?></span>
                </nav><!-- .nav-single -->

                <?php comments_template( \'\', true ); ?>

            <?php endwhile; // end of the loop. ?>

        </div><!-- #content -->
    </div><!-- #primary -->

<?php get_sidebar(); ?>
<?php get_footer(); ?>