custom field in checkout page not working with ajax cart woocommerce

I am using this code to add custom ‘agree’ check box in checkout page, it is working with simple checkout in wordpress.

add_action('woocommerce_after_order_notes', 'my_custom_checkout_field');

function my_custom_checkout_field( $checkout ) {

  echo '<div id="my-new-field"><h3>'.__('My Checkbox: ').'</h3>';

  woocommerce_form_field( 'my_checkbox', array(
    'type'          => 'checkbox',
    'class'         => array('input-checkbox'),
    'label'         => __('I have read and agreed.'),
    'required'  => true,
    ), $checkout->get_value( 'my_checkbox' ));

  echo '</div>';
}

/**
 * Process the checkout
**/
add_action('woocommerce_checkout_process', 'my_custom_checkout_field_process');

function my_custom_checkout_field_process() {
    global $woocommerce;

   // Check if set, if its not set add an error.
    if (!$_POST['my_checkbox'])
       $woocommerce->add_error( __('Please agree to my checkbox.') );
}

/**
 * Update the order meta with field value
 **/
add_action('woocommerce_checkout_update_order_meta', 'my_custom_checkout_field_update_order_meta');

function my_custom_checkout_field_update_order_meta( $order_id ) {
    if ($_POST['my_checkbox']) update_post_meta( $order_id, 'My Checkbox', esc_attr($_POST['my_checkbox']));
}

but if i change woocommerce to ajax cart from admin section. my code is not working. so is there any way to work this code with ajax cart in wordpress woocommerce?

Thanks.