appBar: PreferredSize(
        preferredSize: Size.fromHeight(90),
        child: AppBar(
          title: Text(
            'About This App',
            style: TextStyle(fontSize: 28),
          ),
          centerTitle: true,
          backgroundColor: Color(0xffbf360c),
          elevation: 10,
          shadowColor: Color(0xff3f51b5),
          shape: RoundedRectangleBorder(
            borderRadius: BorderRadius.only(
              bottomLeft: Radius.circular(25),
              bottomRight: Radius.circular(25),
            ),
          ),
        ),
      ),