Add custom field in activity page and display the value submitted in the custom field in lightbox

functions.php

<?php
function rtmedia_uploader_before_start_upload_button_callback() {
    global $rtmedia_media;
    ?>  <div> city :<input class="rtmedia_city" id="rtmedia_city" type="text" name="city" value="" /> </div>
    <?php
}
add_action('rtmedia_uploader_before_start_upload_button', 'rtmedia_uploader_before_start_upload_button_callback');


function wp_ajax_rtmedia_add_city_to_media_callback(){
	if( ! function_exists( 'update_rtmedia_meta' ) ) {
		die();
	}
	$media_id = ( !empty( $_POST['media_id'] ) ) ? wp_strip_all_tags( $_POST['media_id'] , true ) : false;
	$media_id = filter_var( $media_id , FILTER_SANITIZE_NUMBER_INT);
	$city = ( !empty( $_POST['city'] ) ) ? wp_strip_all_tags( $_POST['city'], true ) : false;
	if( $media_id  && $city ){
		update_rtmedia_meta( $media_id, 'city', $city );
	}else{
		die( "error" );
	}
}
add_action( 'wp_ajax_rtmedia_add_city_to_media', 'wp_ajax_rtmedia_add_city_to_media_callback' );
add_action( 'wp_ajax_nopriv_rtmedia_add_city_to_media', 'wp_ajax_rtmedia_add_city_to_media_callback' );

function rtmedia_actions_before_description_callback( $media_id ) {
	if( ! function_exists( 'get_rtmedia_meta' ) ) {
		return;
	}
	if( $media_id ){
		$city = get_rtmedia_meta( $media_id, 'city' );
		if( !empty( $city ) ){ ?>
		    <div class="rtmedia-media-city">
		    	<span>City: <?php echo $city; ?></span>
			</div>
			<?php
		}
	}
}
add_action('rtmedia_actions_before_description', 'rtmedia_actions_before_description_callback', 100, 1);

function rtmedia_uploader_before_start_upload_button_script() {
?>
<script type="text/javascript">
  	if ( undefined !== window.jQuery ) {
	    jQuery( 'document' ).ready( function( $ ) {
		    rtMediaHook.register( 'rtmedia_js_after_file_upload', function( $args ) {
		    	var rtmedia_city = jQuery( "#rtmedia_city" ).val();

		    	if( $args[2] && rtmedia_city ){
		    		jQuery.ajax({
						type: "POST",
						url: rtmedia_ajax_url,
						data: {
						    action: 'rtmedia_add_city_to_media',
						    media_id: $args[2],
						    city: rtmedia_city,
						},
						success : function(data){
						}
					});
		    	}
		    });
		});
  	}
</script>
<?php
}
add_action( 'wp_footer', 'rtmedia_uploader_before_start_upload_button_script' );