I made a GridView with children that each has a GestureDetector and a onTap method set. But the onTap event gets called only when the view is created and not when the item has been tapped. What am I doing wrong here?

class MyGridView extends StatelessWidget {

  @override
  Widget build(BuildContext context) {
    return new Column(
        children: <Widget>[
          new Expanded(
              child: new GridView.count(
                  crossAxisCount: 2,
                  children: [
                    new GridItem(0),
                    new GridItem(1)
                  ]
              )
          )
        ]
    );
  }
}

class GridItem extends StatelessWidget {
  final int code;
  GridItem(this.code);

  @override
  Widget build(BuildContext context) {
    return new GestureDetector(
        onTap: print(code),
        child: new Container(
            height: 48.0,
            child: new Text('$code')
        )
    );
  }
}