```dart
class Weather extends StatefulWidget {
  State<Weather> createState() => _WeatherState();
}

class _WeatherState extends State<Weather> {
  Completer<void> _refreshCompleter;

  @override
  void initState() {
    super.initState();
    _refreshCompleter = Completer<void>();
  }

  @override
  Widget build(BuildContext) {
    ...
  }
```
