void Init()
 {
     if (preview == null)
     {
         GameObject obj = GameObject.Find(name);
         if (obj == null)
         {
             GameObject prefab = AssetDatabase.LoadAssetAtPath <GameObject> (
                 SWCommon.ProductFolder() + "/Prefabs/Preview.prefab");
             obj           = GameObject.Instantiate(prefab);
             obj.name      = name;
             obj.hideFlags = HideFlags.HideInHierarchy;
         }
         preview = obj.GetComponent <SWPreview> ();
         preview.Init(startPos);
     }
 }