flutter overlay with opacity

flutter_overlay.dart

Stack(
  children: <Widget>[
    Column(
      children: <Widget>[
        Container(),
        Container(),
      ],
    ),
    _overlay(True)
  ],
),



  Positioned _overlay(bool show){
    return Positioned(
      right: show ? 5.0 : double.infinity,
      top: 0.0,
      left: 0.0,
      bottom: 0.0,
      child: Container(
        color: Colors.white70.withOpacity(0.7),
      ),
    );
  }