attach method

  1. @override
void attach (covariant PipelineOwner owner)
override

Mark this node 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 first call their inherited attach method, and then attach all their children to the same owner.

Implementation 

@override
void attach(PipelineOwner owner) {
  super.attach(owner);
  _opacity.addListener(_updateOpacity);
  _updateOpacity(); // in case it changed while we weren't listening
 }