activatePrevious method
void
activatePrevious()
Activates previous element in the list, if the active item is not already the first item.
Implementation
void activatePrevious() {
if (_items.isEmpty) {
_activeIndex = -1;
} else if (_activeIndex > 0) {
_activeIndex--;
} else if (_loop) {
_activeIndex = _items.length - 1;
}
_modelChanged.add(null);
}