154     lv_obj_t * btn = lv_button_create(parent);  in btn_create()  local
155     lv_obj_set_flex_grow(btn, 1);  in btn_create()
156     lv_obj_set_height(btn, lv_pct(100));  in btn_create()
157     lv_obj_set_style_radius(btn, 0, 0);  in btn_create()
158     lv_subject_add_observer_obj(&current_tab_subject, btn_observer_cb, btn, NULL);  in btn_create()
159     lv_obj_add_event_cb(btn, btn_click_event_cb, LV_EVENT_CLICKED, NULL);  in btn_create()
161     lv_obj_t * label = lv_label_create(btn);  in btn_create()
168     lv_obj_t * btn = lv_event_get_target(e);  in btn_click_event_cb()  local
169     uint32_t idx = lv_obj_get_index(btn);  in btn_click_event_cb()
178     lv_obj_t * btn = lv_observer_get_target(observer);  in btn_observer_cb()  local
179     int32_t idx = (int32_t)lv_obj_get_index(btn);  in btn_observer_cb()
181     if(idx == prev_v) lv_obj_remove_state(btn, LV_STATE_CHECKED);  in btn_observer_cb()
182     if(idx == cur_v) lv_obj_add_state(btn, LV_STATE_CHECKED);  in btn_observer_cb()