对于自定义帖子类型，以“单个”显示附件

我正在使用Types插件来构建自定义帖子类型和自定义分类法，效果很好。现在，我尝试显示某个帖子的内容，并将附件上传到该帖子（仅允许一个，不允许多个），但是我无法使其正常工作。这是我在single-legislacion.php模板上所做的：

<div class="legislacion-col-izq">
    <div class="CajaIzq">
        <?php if ( have_posts() ) : ?>
            <?php while ( have_posts() ) : the_post(); ?>
                <h4><?php the_title(); ?></h4>
            <?php endwhile; ?>
        <?php endif; ?>
        <?php
        $args = array(
            'order'       => 'ASC',
            'post_type'   => 'attachment',
            'post_parent' => the_ID(),
            'post_status' => 'inherit',
            'numberposts' => 1
        );

        $attachments = get_posts( $args );
        if ( $attachments ) {
            foreach ( $attachments as $attachment ) { ?>
                <div class="BaseIco">
                    <a class="IcoDescargas" href="<?php echo wp_get_attachment_url( $attachment->ID, true ); ?>">
                        <img src="<?php echo get_template_directory_uri(); ?>/images/ico_descargas.png"><br>
                        Descargar PDF
                    </a>
                </div>
            <?php }
        }
        ?>
        <div class="ModSuscrip">
            <p class="A">¿Deseas ver comentarios y jurisprudencia sobre esta ley?</p>
            <p class="B"><a href="#">Suscríbete a cualquiera de nuestros planes</a> y podrás ver material
                complementario, enlaces, y mucho más para enreiquecer tu investigación</p>
        </div>
        <?php echo do_shortcode( '[toc label="Índice por Títulos"]' ) ?>
    </div>
</div>
<div class="legislacion-col-der">
    <div class="CajaInfo">
        <div class="titulo">¿Estás buscando una palabra o frase en particular?</div>
        Recuerda que puedes usar la función de búsqueda de tu navegador (Ctrl + F o Command + F)
    </div>
    <div class="CajaContenido">
        <h1 class="titulo"><?php the_title(); ?></h1>
        <?php if ( have_posts() ) : ?>
            <?php while ( have_posts() ) : the_post(); ?>
                <?php $options = get_option( 'responsive_theme_options' ); ?>
                <?php if ( $options['breadcrumb'] == 0 ): ?>
                    <?php echo responsive_breadcrumb_lists(); ?>
                <?php endif; ?>

                <div id="post-<?php the_ID(); ?>">
                    <div class="post-entry">
                        <?php the_content( __( 'Read more &#8250;', 'responsive' ) ); ?>
                        <?php wp_link_pages( array(
                            'before' => '<div class="pagination">' . __( 'Pages:',
                                    'responsive' ),
                            'after'  => '</div>'
                        ) ); ?>
                    </div>
                    <!-- end of .post-entry -->
                    <?php if ( comments_open() ) : ?>
                        <div class="post-data">
                            <?php the_tags( __( 'Tagged with:', 'responsive' ) . ' ', ', ', '<br />' ); ?>
                            <?php the_category( __( 'Posted in %s', 'responsive' ) . ', ' ); ?>
                        </div><!-- end of .post-data -->
                    <?php endif; ?>
                    <div class="post-edit"><?php edit_post_link( __( 'Edit', 'responsive' ) ); ?></div>
                </div><!-- end of #post-<?php the_ID(); ?> -->
                <?php comments_template( '', true ); ?>
            <?php endwhile; ?>
            <?php if ( $wp_query->max_num_pages > 1 ) : ?>
                <?php if ( function_exists( 'wp_paginate' ) ) {
                    wp_paginate();
                } ?>
            <?php endif; ?>
        <?php else : ?>
            <h1 class="title-404"><?php _e( '404 &#8212; Fancy meeting you here!', 'responsive' ); ?></h1>
            <p><?php _e( 'Don&#39;t panic, we&#39;ll get through this together. Let&#39;s explore our options here.',
                    'responsive' ); ?></p>
            <h6><?php printf( __( 'You can return %s or search for the page you were looking for.', 'responsive' ),
                    sprintf( '<a href="%1$s" title="%2$s">%3$s</a>',
                        esc_url( get_home_url() ),
                        esc_attr__( 'Home', 'responsive' ),
                        esc_attr__( '&larr; Home', 'responsive' )
                    ) );
                ?></h6>
            <?php get_search_form(); ?>
        <?php endif; ?>
    </div>
</div>

但是我从任何帖子中都得到了附件，而不是这篇文章的附件，我怎么知道？因为帖子上的URL是这个URL，http://project.dev/wp-content/uploads/2014/12/file.pdf而我在前面得到了这个URL，所以http://project.dev/wp-content/uploads/2013/08/SC-1081-30.docx怎么了？我如何获得该CPT的附件？