ScaleTransition from a Card to Full Screen Widget

I have a grid of cards that on onTap, I would like it to Expand to fill the screen. Just like on iOS when we click on a app launcher icon.

I manage to get it to expand, but it is always from the middle of the screen, with this:

 onTap: () {
        Navigator.of(context).push(new PageRouteBuilder(pageBuilder:
            (BuildContext context, Animation animation,
                Animation secondaryAnimation) {
          return MyWidget();
        }, transitionsBuilder: (BuildContext context,
            Animation<double> animation,
            Animation<double> secondaryAnimation,
            Widget child) {
          return Align(
            child: ScaleTransition(
              child: child,
              scale: animation,
            ),
          );
        }));
      }

I saw that ScaleTransition have a alignment, but I couldn't figure out how to use that to set it to the point in the middle of my Card.