add lv_obj_get_type

lv_objx/lv_slider.c

@@ -443,6 +443,14 @@ static lv_res_t lv_slider_signal(lv_obj_t * slider, lv_signal_t sign, void * par
             if(ext->action != NULL) ext->action(slider);
         }
     }
+    else if(sign == LV_SIGNAL_GET_TYPE) {
+        lv_obj_type_t * buf = param;
+        uint8_t i;
+        for(i = 0; i < LV_MAX_ANCESTOR_NUM - 1; i++) {  /*Find the last set data*/
+            if(buf->type[i] == NULL) break;
+        }
+        buf->type[i] = "lv_slider";
+    }
 
     return res;
 }