在Drupal8的控制器中编辑自定义模块的配置变量

mymodule_api_key: 'default_value'

namespace Drupal\mymodule\Form;

use Drupal\Core\Form\ConfigFormBase;
use Drupal\Core\Form\FormStateInterface;

class MyModuleSettingsForm extends ConfigFormBase {

  /**
   * {@inheritdoc}
   */
  protected function getEditableConfigNames() {
    return ['mymodule.settings'];
  }

  /**
   * {@inheritdoc}
   */
  public function getFormId() {
    return 'mymodule_settings_form';
  }

  /**
   * {@inheritdoc}
   */
  public function buildForm(array $form, FormStateInterface $form_state) {
    $config = $this->config('mymodule.settings');

    $form['mymodule_api_key'] = [
      '#type' => 'textfield',
      '#title' => $this->t('API Key'),
      '#default_value' => $config->get('mymodule_api_key'),
    ];

    return parent::buildForm($form, $form_state);
  }

  /**
   * {@inheritdoc}
   */
  public function submitForm(array &$form, FormStateInterface $form_state) {
    $config = $this->config('mymodule.settings');
    $config->set('mymodule_api_key', $form_state->getValue('mymodule_api_key'));
    $config->save();

    parent::submitForm($form, $form_state);
  }

}

mymodule.settings_form:
  path: '/admin/config/mymodule/settings'
  defaults:
    _form: '\Drupal\mymodule\Form\MyModuleSettingsForm'
    _title: 'MyModule Settings'
  requirements:
    _permission: 'administer site configuration'