Just wrap InkWell() in Material()
// Example: Material(child: InkWell(onTap: (){}))
InkWell(
splashColor: Colors.grey,
onTap: () {
Future.delayed(const Duration(milliseconds: 300), () {
Navigator.push(
context, MaterialPageRoute(builder: (context) => NextPage()));
});
},
child:Somewidget,
)