使用当前ID发布子内容

Question

I have this loop that displays the child of a parent though this is working. Generally I want this to be converted dynamically main problem is, I only want to display the child of the current Page using it's ID.

        <?php
        $args = array(
            'post_type' => 'page',
            'post_status' => 'publish',
            'posts_per_page' => -1,
            'post_parent' => ,
            'orderby'=> 'menu_order',
            'order'=> 'asc',
        );
        $query = new WP_Query($args);
        $catNull = get_template_directory_uri();
        echo '<ul class="all-service">';
        while ($query->have_posts()) {
            $query->the_post(); ?>
            <li class="all-service-item">
                <a href="<?php the_permalink(); ?>">
                <div class="content">
                    <h4><?php the_title(); ?></h4>  
                    <?php the_content(); ?>
                </div></a>
            </li>
            <?php
        }
        wp_reset_postdata();?>
        </ul>

I'm using the post_parent => then e.g. '1' the ID of the parent but I want this basically to be the_ID() which is the current ID problem is its rendering all of the ID not the current one. Not quite sure if I have to convert the_ID to a variable to load it as string not constant.

Code below generates all post and page then display whatever is declared on the loop

    <?php
    $args = array(
        'post_type' => 'page',
        'post_status' => 'publish',
        'posts_per_page' => -1,
        'post_parent' => the_ID,
        'orderby'=> 'menu_order',
        'order'=> 'asc',
    );
    $query = new WP_Query($args);
    $catNull = get_template_directory_uri();
    echo '<ul class="all-service">';
    while ($query->have_posts()) {
        $query->the_post(); ?>
        <li class="all-service-item">
            <a href="<?php the_permalink(); ?>">
            <div class="content">
                <h4><?php the_title(); ?></h4>  
                <?php the_content(); ?>
            </div></a>
        </li>
        <?php
    }
    wp_reset_postdata();?>