Change the text on button

How-to
2

Try:

static lv_obj_t *btn, *label;

static void btn_handler(lv_event_t *e)
{
  lv_event_code_t code = lv_event_get_code(e);

  if (code == LV_EVENT_CLICKED)
  {
    lv_label_set_text(label, "Clicked!");
  }
}

btn = lv_btn_create(parent);
lv_obj_add_event_cb(btn, btn_handler, LV_EVENT_ALL, NULL);

label = lv_label_create(btn);
lv_label_set_text(label, "Click on button");

You can also do this using the lv_event_get_user_data function.