WP_list_table prepare_items()

I create custom WP_list_table with side form like (adding new category form), but when i submit that form wp_list_table doesn’t refresh. When I once again refresh page information appears.I use wp_list_table_example plugin everything is the same except for geting example_data.

function prepare_items() {
        $data = array();
        $example_data = array();
    $terms = get_terms( 'productcat', array('hide_empty' => false));

        if ( ! empty( $terms )  ){
     foreach ( $terms as $term ) {
           $data[] = array(
							'ID'          =>  $term->term_id,
							'title'       => $term->name
							);

     }
 }

        $example_data = $data;

When I once again refresh page information appears, I’m adding new taxonomy like this on form submit

$new_term =  $_POST['term'];
        $description = $_POST['description'];
        wp_insert_term(
          $new_term,
          'productcat',
            array(
    'description'=> $description,
  )
        );

Is it in the way of passing and receiving data problem, and how to submit form and refresh wp_list_table.