class ImageScreen extends StatefulWidget {
  @override
  _ImageScreenState createState() => new _ImageScreenState();
}

class _ImageScreenState extends State<ImageScreen>
    with TickerProviderStateMixin, ImagePickerListener {
  File _image;
...
}

class Overview extends StatefulWidget {
  @override
  State<StatefulWidget> createState() {
    return _overview();
  }
}

class _overview extends State<overview> {
 @override
  Widget build(BuildContext context) {

return Scaffold(
        appBar: topAppBar(_ImageScreenState._image),
        body: Scaffold()
}

class Overview extends StatefulWidget {
    File image ;
    Overview ( this.image) ;

      @override
      State<StatefulWidget> createState() {
        return _overview();
      }
    }

    class ImageScreen extends StatefulWidget {
      @override
      _ImageScreenState createState() => new _ImageScreenState();
    }

    class _ImageScreenState extends State<ImageScreen>
        with TickerProviderStateMixin, ImagePickerListener {
      File _image;

    void _redirect ( ) {
     Navigator.push(
            context,
            MaterialPageRoute(
              builder: (context) => Overview (
                Image: _image,
              ),
            ),
          ); }
    }