将自定义metabox字段添加到类别循环

Question

我试图使帖子的自定义metabox陷入循环，但无法正常工作。我需要在args中通过meta_query进行调用吗？或者我可以直接进入循环？我在wordpress开发人员网站上查看但无法正常工作。

      <?php

      global $post;
      $args = array(
        'posts_per_page'   => 5,
        'offset'           => 0,
        'cat'         => '',
        'category_name'    => 'new-posts',
        'orderby'          => 'date',
        'order'            => 'DESC',
        'include'          => '',
        'exclude'          => '',
        'meta_key'         => 'rd_custom_title',
        'meta_value'       => '',
        'post_type'        => 'post',
        'post_mime_type'   => '',
        'post_parent'      => '',
        'author'       => '',
        'author_name'      => '',
        'post_status'      => 'publish',
        'suppress_filters' => true,
        'fields'           => '',
        'meta_query' => array(
              array(
                  'key' => '_thumbnail_id',
                  'compare' => 'EXISTS'
              ),
          )
      );


      $myposts = get_posts( $args );
      foreach ( $myposts as $post ) : setup_postdata( $post ); ?>
        <li>
          <?php the_post_thumbnail(); ?>
          <?php get_post_meta($post_id, 'rd_custom_title', true); ?>
          <?php get_post_meta($post->ID, 'rd_custom_title', true); ?>
          <a href="<?php the_permalink(); ?>"><?php the_title(); ?></a>
        </li>
      <?php endforeach; 
      wp_reset_postdata();?>