How can I get row field in hook_preprocess_views_view_unformatted(&$variables)?
You find the field handlers you have configured in the Fields list in $view-&gt;field. A field handler has methods like getValue(), render() and advancedRender(), which accept as argument the row variable:

Example:

$view = $variables['view'];
$rows = $variables['rows'];
foreach ($rows as $id =&gt; $row) {
  $field_value = $view-&gt;field['field_name']-&gt;getValue($row);
}


See also Get result view with formatter programmattically