Yii 2—— layout查找顺序

public function findLayoutFile($view)
 {
     $module = $this->module;
     if (is_string($this->layout)) {
         $layout = $this->layout;
     } elseif ($this->layout === null) {
         while ($module !== null &&  $module->layout === null) {
             $module =  $module->module;
         }
         if ($module !== null && is_string($module->layout)) {
             $layout = $module->layout;
         }
     }