Adding the current title to the breadcrumb

We can use hook_system_breadcrumb_alter in .module file to add the current title to breadcrumb.

use Drupal\Core\Breadcrumb\Breadcrumb;
use Drupal\Core\Routing\RouteMatchInterface;
use Drupal\Core\Link;
/**
 * Implements hook_system_breadcrumb_alter().
 */
function mymodule_base_system_breadcrumb_alter(Breadcrumb &$breadcrumb, RouteMatchInterface $route_match, array $context) {
  if ($breadcrumb && !\Drupal::service('router.admin_context')
      ->isAdminRoute()) {
    $title = \Drupal::service('title_resolver')
      ->getTitle(\Drupal::request(), $route_match->getRouteObject());
    if (!empty($title)) {
      $breadcrumb->addLink(Link::createFromRoute($title, '<none>'));
    }
  }
}

If we have more complicated logic for our breadcrumb items and if we have to build almost every item in breadcrumb through some logic then we must develop a custom BreadcrumbBuilder. BreadcrumbBuilder also helps us to build breadcrumbs for views, custom controllers, etc.

Custom BreadcrumbBuilder

File - my_module.services.yml

# File - my_module.services.yml
services:
  my_module.breadcrumb:
    class: Drupal\my_module\BreadcrumbBuilder
    arguments:
      - '@router.admin_context'
    tags:
      - { name: breadcrumb_builder, priority: 100 }

File - /src/BreadcrumbBuilder.php

<?php
namespace Drupal\my_module;
use Drupal\Core\Breadcrumb\Breadcrumb;
use Drupal\Core\Breadcrumb\BreadcrumbBuilderInterface;
use Drupal\Core\Link;
use Drupal\Core\Routing\AdminContext;
use Drupal\Core\Routing\RouteMatchInterface;
use Drupal\Core\StringTranslation\StringTranslationTrait;
use Drupal\node\NodeInterface;
/**
 * Provides custom BreadcrumbBuilder for askhub theme.
 */
class BreadcrumbBuilder implements BreadcrumbBuilderInterface {
  use StringTranslationTrait;
  /**
   * AdminContext service.
   *
   * @var \Drupal\Core\Routing\AdminContext
   */
  protected $adminContext;
  /**
   * Creates a new ThemeNegotiator instance.
   *
   * @param \Drupal\Core\Routing\AdminContext $admin_context
   *   AdminContext service.
   */
  public function __construct(AdminContext $admin_context) {
    $this->adminContext = $admin_context;
  }
  /**
   * {@inheritdoc}
   */
  public function applies(RouteMatchInterface $route_match) {
    $node = $route_match->getParameter('node');
    $view = $route_match->getParameter('view_id');
    $view_display_id = $route_match->getParameter('display_id');
    if (!$this->adminContext->isAdminRoute() &&
      $node instanceof NodeInterface &&
      $node->bundle() == "askhub") {
      return TRUE;
    }
    elseif (!$this->adminContext->isAdminRoute() && 
    $view == 'askhub' && $view_display_id == 'askhub') {
      return TRUE;
    }
    return FALSE;
  }
  /**
   * {@inheritdoc}
   */
  public function build(RouteMatchInterface $route_match) {
    $breadcrumb = new Breadcrumb();
    $breadcrumb->addCacheContexts(['route']);
    // Breadcrumb links.
    $links[] = Link::createFromRoute($this->t('Home'), '<front>');
    // Add current node title.
    $node = $route_match->getParameter('node');
    if ($node instanceof NodeInterface) {
      $links[] = Link::createFromRoute($this->t('Ask Hub'), 'view.askhub.askhub');
      $links[] = Link::createFromRoute($node->getTitle(),
        '<none>');
    }
    else {
      $links[] = Link::createFromRoute($this->t('Ask Hub'), '<none>');
    }
    $breadcrumb->setLinks($links);
    return $breadcrumb;
  }
}