void showOverlay(BuildContext context) async {
    final OverlayState overlayState = Overlay.of(context);
    final OverlayEntry overlayEntry = OverlayEntry(
      builder: (BuildContext context)=>Positioned(
        left: 0.0,
        right: 0,
        bottom: 90.0,
        child: Container(
            margin: const EdgeInsets.all(15.0),
            padding: const EdgeInsets.all(3.0),
            decoration: BoxDecoration(
              borderRadius: BorderRadius.circular(25.0),
                border: Border.all(color: Colors.blueAccent)
            ),
          child:
                Text('Focus, lighting and contrast help',style: TextStyle(fontWeight: FontWeight.normal,
                    color: Colors.white,
                    fontSize: 18.0,
                    decoration: TextDecoration.none)),

          )
        ),
    );
    overlayState.insert(overlayEntry);
    await Future<dynamic>.delayed(Duration(seconds: 2));
    overlayEntry.remove();

  }