anchor.diff:  
     @override
     Widget build(BuildContext context) {
  -    return Center(
  -      alignment: Alignment.center,
  -      child: Column(
  -        mainAxisAlignment: MainAxisAlignment.center,
  -        children: <Widget>[
  -          if (errorMsg != null) Text(errorMsg),
  -          RaisedButton(
  -            color: Colors.redAccent,
  -            child: const Text('Try again'),
  -            onPressed: () async {
  -              await handler.fetchAndDispatch();
  -            },
  -          ),
  -        ],
  -      ),
  +    return Column(
  +      mainAxisAlignment: MainAxisAlignment.center,
  +      children: <Widget>[
  +        if (errorMsg != null) Text(errorMsg),
  +        RaisedButton(
  +          color: Colors.redAccent,
  +          child: const Text('Try again'),
  +          onPressed: () async {
  +            await Provider.of<_PlanetHandler>(context, listen: false)
  +                .fetchAndDispatch();
  +          },
  +        ),
  +      ],
       );
     }
   }
  
positive.code:         }
  
          final planet = state.planetPage.results[index - 1];
          return ListTile(
            title: Text(planet.name),
          );
        },
      );
    }
  
negative.code:   @override
    Widget build(BuildContext context) {
      final state = Provider.of<AppState>(context);
      MainAxisAlignment buttonAlignment;
      if (state.planetPage.previous == null) {
        buttonAlignment = MainAxisAlignment.end;
      } else if (state.planetPage.next == null) {
        buttonAlignment = MainAxisAlignment.start;
      } else {
        buttonAlignment = MainAxisAlignment.spaceBetween;
      }
  
      return Row(
        mainAxisAlignment: buttonAlignment,
        children: <Widget>[
          if (state.planetPage.previous != null) _LoadPageButton(next: false),
          if (state.planetPage.next != null) _LoadPageButton(next: true)
        ],
      );
    }
  }
  