createChild method

@override void createChild(TKey nodeId)

Creates or updates the child for the given node.

Implementation

@override
void createChild(TKey nodeId) {
  assert(_inLayout, 'createChild must be called during layout');
  final existing = _children[nodeId];
  // Three cases handled here:
  //   1. No existing element: build a fresh widget via [nodeBuilder].
  //   2. Existing element, queued as dirty by a prior update / notify:
  //      rebuild with a fresh widget so the row picks up any new state
  //      captured by the `nodeBuilder` closure or new controller data.
  //   3. Existing element, not dirty: no-op — this is the hot path
  //      every layout hits for already-mounted cache-region keys.
  final needsRefresh = existing != null && _dirtyKeys.remove(nodeId);
  if (existing != null && !needsRefresh) {
    return;
  }
  owner!.buildScope(this, () {
    final nodeData = widget.controller.getNodeData(nodeId);
    if (nodeData == null) {
      return;
    }
    final depth = widget.controller.getDepth(nodeId);
    final childWidget = widget.nodeBuilder(this, nodeId, depth);
    final element = updateChild(existing, childWidget, nodeId);
    if (element != null) {
      _children[nodeId] = element;
    } else if (existing != null) {
      _children.remove(nodeId);
    }
  });
}