moveRight method
void
moveRight()
Moves focus right by one cell with wrapping.
At the end of a row, wraps to the start of the next row. At the last item, wraps to item 0.
Implementation
void moveRight() {
if (_itemCount == 0) return;
_focusedIndex = _focusedIndex == _itemCount - 1 ? 0 : _focusedIndex + 1;
}