hook_element_info_alter

修改元素的默认值

function hook_element_info_alter(array &$info) {
  // 判断元素textfield是否有size属性，有的话设置大小为40
  if (isset($info['textfield']['#size'])) {
    $info['textfield']['#size'] = 40;
  }
}
function hook_element_info_alter(array &$info) {
  // 判断元素是否是submit，为真添加自定义class
  if (isset($info['submit'])) {
    $info['submit']['#attributes']['class'] = 'btn btn-success';
  }
}

hook_form_system_theme_settings_alter

更改主题特定的设置表单
添加表单元素，更改默认值，删除表单元素

function hook_form_system_theme_settings_alter(&$form, \Drupal\Core\Form\FormStateInterface $form_state) {
  // Add a checkbox to toggle the breadcrumb trail.
  $form['toggle_breadcrumb'] = [
    '#type' => 'checkbox',
    '#title' => t('Display the breadcrumb'),
    '#default_value' => theme_get_setting('features.breadcrumb'),
    '#description' => t('Show a trail of links from the homepage to the current page.'),
  ];
}

hook_theme_suggestions_HOOK

提供备用主题命名建议

function hook_theme_suggestions_HOOK(array $variables) {
  $suggestions = [];
  $suggestions[] = 'hookname__' . $variables['elements']['#langcode'];
  return $suggestions;
}

hook_theme_suggestions_HOOK_alter

主题钩子命名的建议

它会重新排序或删除由hook_theme_suggestions_HOOK提供的建议或先调用此钩子

function hook_theme_suggestions_HOOK_alter(array &$suggestions, array $variables) {
  if (empty($variables['header'])) {
    $suggestions[] = 'hookname__' . 'no_header';
  }
}

hook_theme_suggestions_alter

更改所有主题钩子命名建议

function MYMODULE_theme_suggestions_alter(array &$suggestions, array $variables, $hook) {
    // 根据登录的用户为节点和分类术语模板提供了替代模板建议
  if (\Drupal::currentUser()->isAuthenticated() && in_array($hook, array('node', 'taxonomy_term'))) {
    $suggestions[] = $hook . '__' . 'logged_in';
  }
}
function hook_theme_suggestions_alter(array &$suggestions, array $variables, $hook) {
  // Add an interface-language specific suggestion to all theme hooks.
  $suggestions[] = $hook . '__' . \Drupal::languageManager()->getCurrentLanguage()->getId();
}

hook_css_alter

更改css文件

function hook_css_alter(&$css, \Drupal\Core\Asset\AttachedAssetsInterface $assets) {
  // Remove defaults.css file.
  unset($css[drupal_get_path('module', 'system') . '/defaults.css']);
}

hook_page_attachments

将资源库添加到页面中

function hook_page_attachments(array &$attachments) {
  // Unconditionally attach an asset to the page.
  $attachments['#attached']['library'][] = 'core/domready';

  // Conditionally attach an asset to the page.
  if (!\Drupal::currentUser()->hasPermission('may pet kittens')) {
    $attachments['#attached']['library'][] = 'core/jquery';
  }
}

hook_page_attachments_alter

删除或者更改页面的资源库，或者将附件添加到依赖于另一个模块附件的页面上

此钩子在hook_page_attachments()之后运行

function hook_page_attachments_alter(array &$attachments) {
  // Conditionally remove an asset.
  if (in_array('core/jquery', $attachments['#attached']['library'])) {
    $index = array_search('core/jquery', $attachments['#attached']['library']);
    unset($attachments['#attached']['library'][$index]);
  }
}