OpmlFeedAdd::buildForm

public OpmlFeedAdd::buildForm(array $form, FormStateInterface $form_state)

public function buildForm(array $form, FormStateInterface $form_state) {
  $intervals = array(900, 1800, 3600, 7200, 10800, 21600, 32400, 43200, 64800, 86400, 172800, 259200, 604800, 1209600, 2419200);
  $period = array_map(array(\Drupal::service('date.formatter'), 'formatInterval'), array_combine($intervals, $intervals));

  $form['upload'] = array(
    '#type' => 'file',
    '#title' => $this->t('OPML File'),
    '#description' => $this->t('Upload an OPML file containing a list of feeds to be imported.'),
  );
  $form['remote'] = array(
    '#type' => 'url',
    '#title' => $this->t('OPML Remote URL'),
    '#maxlength' => 1024,
    '#description' => $this->t('Enter the URL of an OPML file. This file will be downloaded and processed only once on submission of the form.'),
  );
  $form['refresh'] = array(
    '#type' => 'select',
    '#title' => $this->t('Update interval'),
    '#default_value' => 3600,
    '#options' => $period,
    '#description' => $this->t('The length of time between feed updates. Requires a correctly configured <a href=":cron">cron maintenance task</a>.', array(':cron' => $this->url('system.status'))),
  );

  $form['actions'] = array('#type' => 'actions');
  $form['actions']['submit'] = array(
    '#type' => 'submit',
    '#value' => $this->t('Import'),
  );

  return $form;
}