setFirstFocus method Null safety

void setFirstFocus(
  1. FocusScopeNode scope
)

Make the given scope the active child scope for this scope.

If the given scope is not yet a part of the focus tree, then add it to the tree as a child of this scope. If it is already part of the focus tree, the given scope must be a descendant of this scope.

Implementation

void setFirstFocus(FocusScopeNode scope) {
  assert(scope != null);
  assert(scope != this, 'Unexpected self-reference in setFirstFocus.');
  assert(_focusDebug('Setting scope as first focus in $this to node:', <String>[scope.toString()]));
  if (scope._parent == null) {
    _reparent(scope);
  }
  assert(scope.ancestors.contains(this), '$FocusScopeNode $scope must be a child of $this to set it as first focus.');
  if (hasFocus) {
    scope._doRequestFocus(findFirstFocus: true);
  } else {
    scope._setAsFocusedChildForScope();
  }
}