--- /dev/null
+<?php
+
+namespace Drupal\image_module_test\Plugin\Field\FieldWidget;
+
+use Drupal\Core\Ajax\AjaxResponse;
+use Drupal\Core\Field\FieldItemListInterface;
+use Drupal\Core\Field\WidgetBase;
+use Drupal\Core\Form\FormStateInterface;
+
+/**
+ * Default widget for Dummy AJAX test.
+ *
+ * @FieldWidget(
+ * id = "image_module_test_dummy_ajax_widget",
+ * label = @Translation("Dummy AJAX widget"),
+ * field_types = {
+ * "image_module_test_dummy_ajax"
+ * },
+ * multiple_values = TRUE,
+ * )
+ */
+class DummyAjaxWidget extends WidgetBase {
+
+ /**
+ * {@inheritdoc}
+ */
+ public function formElement(FieldItemListInterface $items, $delta, array $element, array &$form, FormStateInterface $form_state) {
+ $element['select_widget'] = [
+ '#type' => 'select',
+ '#title' => $this->t('Dummy select'),
+ '#options' => ['pow' => 'Pow!', 'bam' => 'Bam!'],
+ '#required' => TRUE,
+ '#ajax' => [
+ 'callback' => get_called_class() . '::dummyAjaxCallback',
+ 'effect' => 'fade',
+ ],
+ ];
+
+ return $element;
+ }
+
+ /**
+ * Ajax callback for Dummy AJAX test.
+ *
+ * @param array $form
+ * The build form.
+ * @param \Drupal\Core\Form\FormStateInterface $form_state
+ * The form state.
+ *
+ * @return \Drupal\Core\Ajax\AjaxResponse
+ * Ajax response.
+ */
+ public static function dummyAjaxCallback(array &$form, FormStateInterface $form_state) {
+ return new AjaxResponse();
+ }
+
+}