attach method
Mark this render object as attached to the given owner.
Typically called only from the parent's attach method, and by the
owner
to mark the root of a tree as attached.
Subclasses with children should override this method to
attach all their children to the same owner
after calling the inherited method, as in super.attach(owner)
.
Implementation
@override
void attach(PipelineOwner owner) {
super.attach(owner);
_controller.addListener(markNeedsLayout);
}