drupal 8 中block系统由plugin API和entity API组成。也就是说即有可重用特性，又有fieldable特性。

Block最小化实现

.info.yml

src/Plugin/Block/ExampleEmptyBlock.php

/**
 * Provides a 'Example: empty block' block.
 *
 * @Block(
 *   id = "example_empty",
 *   admin_label = @Translation("Example: empty block")
 * )
 */
class ExampleEmptyBlock extends BlockBase {
  /**
   * {@inheritdoc}
   */
  public function build() {
    // We return an empty array on purpose. The block will thus not be rendered
    // on the site. See BlockExampleTest::testBlockExampleBasic().
    return array('#markup' => t('empty block'));
  }
}

练习

.info.yml

rotate_image_block.module

/**
* Implements hook_theme().
*/
function rotate_image_block_theme($existing, $type, $theme, $path) {
  return array(
      'rotate_image_block' => array(
          'variables' => array('image_path' => NULL),
          'template' => 'rotate-image-block',
      ),
  );
}

templates/rotate-image-block.html.twig

1	<img class="rotate" src="{{ image_path }}"/>

src/Plugin/Block/RotateImageBlock.php

<?php
namespace Drupal\rotate_image_block\Plugin\Block;
use Drupal\Core\Block\BlockBase;
use Drupal\Core\Form\FormStateInterface;
use Drupal\file\Entity\File;
/**
 * Provides a 'Example: configurable text string' block.
 *
 * Drupal\Core\Block\BlockBase gives us a very useful set of basic functionality
 * for this configurable block. We can just fill in a few of the blanks with
 * defaultConfiguration(), blockForm(), blockSubmit(), and build().
 *
 * @Block(
 *   id = "rotate_image_block",
 *   admin_label = @Translation("Rotate image")
 * )
 */
class RotateImageBlock extends BlockBase {
  /**
   * {@inheritdoc}
   */
  public function blockForm($form, FormStateInterface $form_state) {
    $form['icon_upload'] = array(
      '#type' => 'managed_file',
      '#title' => $this->t('Icon image'),
      '#description' => $this->t('If you\'d like an image to display next to this menu item, upload it here.'),
        '#upload_validators'  => array(
            'file_validate_extensions' => array('gif png jpg jpeg svg'),
        ),
       '#upload_location' => 'public://menu_icons/',
        '#default_value' => ["3"],
    );
    return $form;
  }
  /**
   * {@inheritdoc}
   */
  public function blockSubmit($form, FormStateInterface $form_state) {
      // First we just grab the file ID for the icon we uploaded, if any.
      $icon_field = $form_state->getValue('icon_upload');
      $file_id = empty($icon_field) ? FALSE : reset($icon_field);
      if (!empty($file_id)) {
          // Make this a permanent file so that cron doesn't delete it later.
          $file = File::load($file_id);
          $file->status = FILE_STATUS_PERMANENT;
          $file->save();
          // Grab the image's path for referencing it as a background image.
          $image_path = $file->getFileUri();
          $path = file_url_transform_relative(file_create_url($image_path));
          $this->configuration['image_path'] = $path;
      }
  }
  /**
   * {@inheritdoc}
   */
  public function build() {
    return array(
      '#theme' => 'rotate_image_block',
      '#image_path' => $this->configuration['image_path'],
    );
  }
}

Create a form block which can send an e-mail to an address provided in the form. (block form)

.info.yml

src/Form/SimpleForm.php
定义Form，用来输入email

  public function buildForm(array $form, FormStateInterface $form_state) {
    $form['email'] = [
      '#type' => 'email',
      '#title' => $this->t('email'),
      '#description' => $this->t('Title must be a valid email address.'),
      '#required' => TRUE,
    ];
    // Group submit handlers in an actions element with a key of "actions" so
    // that it gets styled correctly, and so that other modules may add actions
    // to the form. This is not required, but is convention.
    $form['actions'] = [
      '#type' => 'actions',
    ];
    // Add a submit button that handles the submission of the form.
    $form['actions']['submit'] = [
      '#type' => 'submit',
      '#value' => $this->t('Submit'),
    ];
    return $form;
  }
  public function getFormId() {
    return 'send_email_block_simple_form';
  }
  public function submitForm(array &$form, FormStateInterface $form_state) {
    /*
     * This would normally be replaced by code that actually does something
     * with the title.
     */
    $email = $form_state->getValue('email');
      $newMail = \Drupal::service('plugin.manager.mail');
      $params['email'] = $email;
      $newMail->mail('send_email_block', 'send_email', $email, 'en', $params, $reply = NULL, $send = TRUE);
      drupal_set_message('Mail has been sent.', 'status');
  }
}

src/Plugin/Block/SendEmailBlock.php
render SimpleForm到block

public function build() {
  $form = \Drupal::formBuilder()->getForm('Drupal\send_email_block\Form\SimpleForm');
  return $form;
}

send_email_block.module
实现hook_mail构建mail内容


function send_email_block_mail($key, &$message, $params) {
    // E-mail formatting will be exactly as below, so do not use indenting!
    $body =
        "Hi,
I'm just showing off my work ...
Works nicely huh?
Should probably add a password here somewhere?
Your username: " . $params['email'] . "
See ya!";
    $message['subject'] = "Exercise account registration";
    $message['body'][] = Drupal\Core\Mail\MailFormatHelper::htmlToText($body);
}

发送mail方法参照这里

参考资料

Blocks, Configuration, and Forms

Block最小化实现

练习

Create a block which displays a rotating banner of images.(Block configuration)

Create a form block which can send an e-mail to an address provided in the form. (block form)

参考资料