最后我解决了这个问题。下面是下载按钮的代码。将此代码放入您的post循环中，它将显示一个下载按钮。

     <form action="<?php echo esc_url( home_url( \'/your_redirected_page_slug\' ) ); ?>" method="GET" id="form1">
    <?php  global $post;
         //$post_slug=$post->post_name;

    ?>
    <input id="myButton" type="submit" name="a" value="Download" class="single-download-button" />
     <input type="hidden" name="appk" id="mkval" value="<?php echo get_the_ID(); ?>" />                                                  
 </form>

<?php
$id = $_GET[\'appk\']; // get form data 
$popularpost = new WP_Query( array(\'post_type\' => \'your_cusom_post_name\',
     \'posts_per_page\' => 9, 
     // \'meta_key\' => \'wpb_post_views_count\', 
     //\'orderby\' => \'meta_value_num\',                               
     \'order\' => \'DESC\',
     \'p\' => $id, 
      ) );


    while ( $popularpost->have_posts() ) : $popularpost->the_post();
    $id = get_the_ID();

    ?>


    <!-- Your Code Function here -->

<?php
    endwhile;
    // Reset Post Data
        wp_reset_postdata();
    ?>