performLayout method
Override this method to lay out and position all children given this widget's size.
This method must call layoutChild for each child. It should also specify the final position of each child with positionChild.
Implementation
@override
void performLayout(Size size) {
for (var itemIndex = 0; itemIndex < sizedItems.length;) {
final item = sizedItems.elementAt(itemIndex);
final itemPos = itemsPosition.elementAt(itemIndex);
layoutChild(item.id, BoxConstraints.tight(Size(item.width, item.height)));
positionChild(item.id, itemPos);
itemIndex++;
}
}