Event callback function error occurs everytime

How-to
9

Please note that v8 is not released yet and thus the documentation is not complete. If you are looking for complete documentation and stability, I recommend continuing to use the release/v7 branch.

As I noted in your previous post, at least part of the issue is that your event handler signature is incorrect. Event handlers now take one parameter (lv_event_t *). Here is an example:

static void event_handler(lv_event_t *e)
{
    LV_UNUSED(obj);
    if(e->code == LV_EVENT_CLICKED) {
        LV_LOG_USER("Clicked");
    }
    else if(e->code == LV_EVENT_VALUE_CHANGED) {
        LV_LOG_USER("Toggled");
    }
}