know whether index is seen or not gridview flutter code example

Example: gridview flutter get index

class Grid4 extends StatelessWidget {
  void tapped(int index){
    if(index == 1){
      print("huray 1");
    } else {
      print("not the one :(");
    }
  }
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(),
      body: Container(
        padding: const EdgeInsets.symmetric(horizontal: 20.0, vertical: 10),
        color: Colors.orange,
        child: GridView.builder(
          itemCount: 25,
          itemBuilder: (context, index) =>
              GestureDetector(
                  onTap: () => tapped(index),
                  child: Container(decoration: BoxDecoration(
                          color: Colors.white70, shape: BoxShape.circle))),
          gridDelegate: SliverGridDelegateWithFixedCrossAxisCount(
            crossAxisCount: 5,
            mainAxisSpacing: 40,
            crossAxisSpacing: 50,
          ),
        ),
      ),
    );
  }
}