Flutter 从下向下动画打开新页面

void _onPress(int id) {
    Navigator.of(context)
        .push(new PageRouteBuilder(pageBuilder: (context, _, __) {
      return new ChildOnePage(id);
    }, transitionsBuilder: (_, Animation<double> animation, __, Widget child) {
      return new FadeTransition(
        opacity: animation,
        child: new SlideTransition(
          position:
              new Tween<Offset>(begin: const Offset(0.0, 1.0), end: Offset.zero)
                  .animate(animation),
          child: child,
        ),
      );
    }));
  }