SizedBox(width: 200.0, height:100.0, 
  child: Shimmer.fromColors(
    baseColor: Colors.red,
    highlightColor: Colors.yellow,
    child: Text('Shimmer', 
      textAlign: TextAlign.center,
      style: TextStyle(
        fontSize: 40.0, fontWeight: FontWeight.bold,
      ),
    ),
  ),
)l