reparentScopeIfNeeded method

void reparentScopeIfNeeded (FocusScopeNode child)

Adopts the given scope if it is the first focus of another scope.

A widget that sets a scope as the first focus of another scope should call this method during its build method in case the widget is moved from one location in the tree to another location that has a different focus scope.

If the given scope is not the first focus of its old parent, the scope is simply detached from its old parent.

Implementation 

void reparentScopeIfNeeded(FocusScopeNode child) {
  assert(child != null);
  if (child._parent == null || child._parent == this)
    return;
  if (child.isFirstFocus)
    setFirstFocus(child);
  else
    child.detach();
}