performRebuild method

Implementation

@override
void performRebuild() {
  _childWidgets.clear(); // Reset the cache, as described above.
  super.performRebuild();
  _currentBeforeChild = null;
  assert(_currentlyUpdatingChildIndex == null);
  try {
    void processElement(int index) {
      _currentlyUpdatingChildIndex = index;
      final Element newChild = updateChild(_childElements[index], _build(index), index);
      if (newChild != null) {
        _childElements[index] = newChild;
        final SliverMultiBoxAdaptorParentData parentData = newChild.renderObject.parentData;
        if (!parentData.keptAlive)
          _currentBeforeChild = newChild.renderObject;
      } else {
        _childElements.remove(index);
      }
    }
    // processElement may modify the Map - need to do a .toList() here.
    _childElements.keys.toList().forEach(processElement);
    if (_didUnderflow) {
      final int lastKey = _childElements.lastKey() ?? -1;
      processElement(lastKey + 1);
    }
  } finally {
    _currentlyUpdatingChildIndex = null;
  }
}