AnimatedContainer with FutureBuilder

main.dart

FutureBuilder(
  future: future,
  builder: (BuildContext context, AsyncSnapshot<String> snapshot) {
    double width;
    switch(snapshot.connectionState) {
      case ConnectionState.none:
      case ConnectionState.waiting:
      case ConnectionState.active:
        width = 0;
        break;
      case ConnectionState.done:
        width = 500;
        break;
    }
    return AnimatedContainer(
      width: width,
      child: Image.asset('assets/star.png'),
      duration: Duration(seconds: 1),
    );
  }
),