anchor.diff:  ///     _nodeAttachment.reparent();
   ///     return GestureDetector(
   ///       onTap: () {
  -///         if (_node.hasFocus) {
  -///           setState(() {
  +///         if (_focused) {
   ///             _node.unfocus();
  -///           });
   ///         } else {
  -///           setState(() {
  -///             _node.requestFocus();
  -///           });
  +///            _node.requestFocus();
   ///         }
   ///       },
   ///       child: Center(
   ///         child: Container(
   ///           width: 400,
   ///           height: 100,
  -///           color: _node.hasFocus ? _color : Colors.white,
  +///           color: _focused ? _color : Colors.white,
   ///           alignment: Alignment.center,
   ///           child: Text(
  -///               _node.hasFocus ? "I'm in color! Press R,G,B!" : 'Press to focus'),
  +///               _focused ? "I'm in color! Press R,G,B!" : 'Press to focus'),
   ///         ),
   ///       ),
   ///     );
  
positive.code: ///
  /// class _ColorfulButtonState extends State<ColorfulButton> {
  ///   FocusNode _node;
  ///   FocusAttachment _nodeAttachment;
  ///   Color _color = Colors.white;
  ///
  
negative.code: ///   void initState() {
  ///     super.initState();
  ///     _node = FocusNode(debugLabel: 'Button');
  ///     _node.addListener(_handleFocusChange);
  ///     _nodeAttachment = _node.attach(context, onKey: _handleKeyPress);
  ///   }
  ///
  ///   void _handleFocusChange() {
  ///     if (_node.hasFocus != _focused) {
  ///       setState(() {
  ///         _focused = _node.hasFocus;
  ///       });
  ///     }
  ///   }
  ///
  ///   bool _handleKeyPress(FocusNode node, RawKeyEvent event) {
  